What is the Alexander technique

The Alexander technique is a taught self-care method that helps people enhance their control of reaction and improve their way of going about everyday activities ¹⁾. Alexander technique uses enhanced kinesthetic awareness and voluntary inhibition to prevent non-beneficial movement patterns ²⁾. The primary focus is put on the relationship between head, neck and back as crucial in effecting an overall integrated pattern of coordinated behavior. Through this conscious re-education of thinking and moving unnecessary muscle tension is released, which leads to more ease in movement and breathing and a better coordinated “use” (technical Alexander technique term describing the manner in which a person moves and behaves). Alexander technique is usually taught one-to-one by licensed teachers and combines verbal instructions with hands-on guidance. The psychophysical connection through hands-on work is specific for Alexander technique and distinguishes it from bodywork techniques.

Alexander technique has been defined as “lessons in proprioceptive musculoskeletal education (without exercises)” but can be more simply described as a type of taught therapy involving a series of movements designed to correct posture and bring the body into natural alignment with the object of helping it to function efficiently ³⁾ and is reported to aid relaxation ⁴⁾. At the end of the 19th century the Australian actor Frederick Matthias Alexander developed this technique in order to improve his voice ⁵⁾. The Alexander technique increases your awareness of body position and movement, eliminating bad habits of posture, muscle tension and movement. The Alexander technique is a ‘re-education’ method rather than a therapy, and practitioners call themselves teachers.

The main principles of the Alexander technique are:

• “how you move, sit and stand affects how well you function”
• “the relationship of the head, neck and spine is fundamental to your ability to function optimally”
• “becoming more mindful of the way you go about your daily activities is necessary to make changes and gain benefit”
• “the mind and body work together intimately as one, each constantly influencing the other”

Teachers of the Alexander technique say that conditions such as backache and other sorts of long-term pain are often the result of misusing your body over a long period of time, such as moving inefficiently and standing or sitting with your weight unevenly distributed.

The aim of the Alexander technique is to help you “unlearn” these bad habits and achieve a balanced, more naturally aligned body.

According to n Alexander Technique website ⁶⁾ – “the Alexander Technique is a skill for self-development teaching you to change long-standing habits that cause unnecessary tension in everything you do.” The chief principle underlying Alexander technique can be expressed as: “use affects functioning.” By this reasoning, it can also be said that mis-use results in dysfunction. Alexander technique sets out to “re-educate” the body to a state of liberated capacity for movement and uninhibited, efficient respiration. Because results of Alexander technique training include, in many cases, the decrease of stress and its documented constricting effects on thoracic function, it is argued those who suffer from illnesses which have emotional or stress-related components also stand to gain particular benefits from Alexander technique ⁷⁾.

Everyday things like tensing when the phone rings, rushing to pick up the children from school or worrying about deadlines lead to physical and mental strain. Over the years, this accumulates and can cause illness, injury or common aches and pains that may seem to come from nowhere. Working with your Alexander Technique teacher, you will learn to recognize your usual reactions to the stresses of life. You will find out how you have been contributing to your problems, how to prevent them and regain control.

The Alexander Technique is a taught self-care method that helps people enhance their control of reaction and improve their way of going about everyday activities. It is usually taught through one-to-one practical lessons involving integrated didactic and hands-on implicit guidance, that enable people to reduce habits associated with musculoskeletal pain ⁸⁾. Applying the Alexander Technique in daily life is associated with improved postural tone, balance, coordination and motor control ⁹⁾, whilst health benefits include long-term improvements in chronic low-back pain ¹⁰⁾. Alexander Technique lessons have been found in a recent trial to be beneficial for people with chronic neck pain at 12 months, however the cost-effectiveness of this intervention is unknown ¹¹⁾.

Alexander technique lessons stimulate your ability to learn simultaneously on different levels; physically, intellectually and emotionally. You learn to recognize your harmful habits, how to stop and think, and to choose a better response. Gradually you learn to apply your new understanding and skill in everyday activities and more complex ones, to bring awareness and poise into everything you do. You learn to become aware of, and then gradually strip away, the habits of movement, tension and reaction that interfere with natural and healthy coordination. Just like riding a bike, once learned, the Alexander technique stays with you for life ¹²⁾.

The Alexander technique teaches you the skilful ”use of the self”, i.e. how you use yourself when moving, resting, breathing, learning, organizing your awareness and focus of attention and, above all, choosing your reactions to increasingly demanding situations.

While Alexander technique is a taught discipline and requires practice, it does not involve physical exercise as the term is generally understood. Leading practitioners of Alexander technique such as the late Dr Wilfred Barlow have maintained that this is particularly important to remember in the case of sufferers from breathing disorders who emphatically do not require, in his words, “breathing exercises” but instead, “breathing education” ¹³⁾.

The Alexander technique is well-known amongst performing artists (musicians, singers and actors in particular) throughout most of the developed world. Many such performers practise Alexander technique regularly, reportedly in order to enhance voice projection and stamina. Linked to these reported benefits are many anecdotes of improvement amongst performers and non-performers with asthma who find that their symptoms and dependence on medication decreases as they become more proficient in Alexander technique ¹⁴⁾. Clinical literature examining the effects of the Alexander technique on respiratory function, however, is scant.

Austin 1992 ¹⁵⁾ reported benefit in a group of ten healthy subjects who received 20 private Alexander technique lessons at weekly intervals, as against a matched control group who received no treatment and showed no significant changes in respiratory function.
There was a significant increase in:

• the highest forced expiratory flow measured with a peak flow meter (PEF) (9%)
• maximum voluntary ventilation (MVV) (6%)
• maximal inspiratory pressure (MIP) (12%)
• maximal expiratory mouth pressure (MEP) (9%)

Calls for empirical studies of Alexander technique have been made by those with an interest in voice disorders following anecdotal reports of its beneficial effects ¹⁶⁾ and these too are suggestive of possible benefits to those who suffer from asthma. Calls for randomized controlled trials in the area of pulmonary/respiratory function and other areas have yet to be heard although progress is being made in other areas, e.g. a planned trial in Parkinsons disease ¹⁷⁾. However, the currently available evidence is insufficient to assess the potential for Alexander technique in the treatment of asthma.

Does Alexander technique work?

Proponents of the Alexander technique often claim it can help people with a wide range of health conditions. Some of these claims are supported by scientific evidence, but some have not yet been properly tested.

There’s evidence suggesting the Alexander technique can help people with:

• long-term back pain – lessons in the Alexander technique may lead to reduced back pain-associated disability and reduce how often you feel pain for up to a year or more ¹⁸⁾
• long-term neck pain – lessons in the Alexander technique may lead to reduced neck pain and associated disability for up to a year or more ¹⁹⁾, ²⁰⁾
• Parkinson’s disease – lessons in the Alexander technique may help you carry out everyday tasks more easily and improve how you feel about your condition ²¹⁾

If you have one of these conditions and are considering trying the Alexander technique, it’s a good idea to speak to your doctor or specialist first to check if it might be suitable for you.

Some research has also suggested the Alexander technique may improve general long-term pain, stammering and balance skills in elderly people to help them avoid falls. But the evidence in these areas is limited and more studies are needed.

There’s currently little evidence to suggest the Alexander technique can help improve other health conditions, including asthma, headaches, osteoarthritis, difficulty sleeping (insomnia) and stress.

Alexander technique risks and limitations

For most people, Alexander technique lessons are safe and pose no health risks. No manipulation of your body is involved, just gentle touch.

However, the technique may not be suitable for certain people, such as those with:

• a specific spinal injury
• severe pain from a herniated (ruptured) disc
• severe spinal stenosis (narrowing of the spine)
• a fracture of the vertebrae (the bones in the spine)

In such cases, specialist medical treatment will be needed.

It’s important to remember that most teachers of the Alexander technique aren’t medical professionals. They do not diagnose, offer advice on or treat conditions that should be managed by a suitably qualified mainstream healthcare professional.

Alexander technique back and neck pain

Neck and back pain together now represent the leading cause of disability in all high income countries, and globally for the 25–64 year age group ²²⁾. Chronic neck pain is regarded as often complex in origin and nature and particularly difficult to manage ²³⁾. Furthermore, the challenge of chronic neck pain is likely to grow due to increasing computer and mobile technology use, with recognized consequences such as ‘text neck’ ²⁴⁾.

A randomized controlled trial ²⁵⁾ designed to examine the effectiveness of the Alexander technique, massage, exercise advice, and behavioral counseling for chronic and recurrent low back pain. The Alexander technique involves assessment of the individual’s normal posture and movements, aiming to release tension from the head, neck and spine, and improve musculoskeletal use when seated and moving. Sixty-four general practitioners surgeries from the south and west of England were recruited to the study. From each surgery a random selection of patients (aged 18 to 65) with chronic or recurrent back pain were invited to participate. Participants had presented to the surgery with back pain more than three months previously (this criteria excluded acute presentations), were suffering pain for three or more weeks and scored above four on the Roland disability scale (number of activities impaired by pain). Patients indicate the number of specified activities or functions limited by back pain (for example, getting out of the house less often, walking more slowly than usual, not doing usual jobs around the house) ²⁶⁾. The Roland disability scale is designed for self report and has good validation characteristics ²⁷⁾. The second primary outcome measure was number of days in pain during the past four weeks (a four week period facilitated recall): this is distinct from intensity of pain or disability ²⁸⁾. The researchers excluded anyone with potential spinal disease, a previous spinal surgery, nerve root pain in the leg, alcohol abuse, a history of psychosis, unable to walk 100m, or who had previous experience in the Alexander technique.

People from each surgery (total of 579) were randomly allocated to one of eight treatment groups (average 72 in each group). Four of the groups were instructed to do extra exercise (doctor prescription of exercises and nurse-led behavioral counseling) along with one of the following treatments: normal care, six sessions of therapeutic massage, six lessons in the Alexander technique, or 24 lessons in the Alexander technique. The other four groups had the same treatments but with no added exercise.

A total of 152 Alexander technique teachers and therapists were involved in educating and carrying out the techniques. People were assessed by postal questionnaire at start of the study, three months, and one year after they had been allocated a treatment. The main outcome that the researchers examined was disability, assessed using the Roland Morris questionnaire and covering issues such as types of activities limited by pain. They also looked at other outcomes of quality of life and other back pain and disability scales.

What were the results of the study?

Of the 579 people who were allocated a group and completed the questionnaire at the beginning of the study, 80% of the study sample (463) completed the one-year follow-up. When they first enrolled in the study, the characteristics of the participants were similar across all treatment groups and the majority had chronic back pain, experiencing 90 or more days of pain over the past year.

At three months, after exercise had been taken into account, Roland disability score and average number of days with back pain over the past month had significantly decreased in all groups compared to control (massages and 6 or 24 Alexander technique lessons). At one year, 6 or 24 Alexander technique lessons had significantly decreased Roland disability score and average number of days with back pain compared to control, but massage no longer showed significant decrease in disability score. The greatest improvement was seen in the 24-lesson group. Compared to control, exercise, following adjustment for the other techniques, significantly decreased both Roland disability score and average number of days with back pain at three months, but at one year, exercise was only significantly effective on disability score.

When the researchers compared individual groups, they found that the effect of 24 Alexander technique lessons combined with exercise was no different to the effect of 24 Alexander technique lessons alone. Six Alexander technique lessons combined with exercise were 72% as effective as 24 lessons alone without exercise. No adverse effects were reported for the Alexander technique.

What interpretations did the researchers draw from these results?

The researchers conclude that one-to-one instruction in the Alexander technique by registered teachers has long-term benefits in chronic back pain. Six lessons combined with exercise had almost comparable effectiveness to 24 lessons in the Alexander technique.

This well conducted randomized trial has strengths in that it involved a large number of participants with a sample size large enough to assess meaningful differences in the measured outcomes for each of the different treatments. It also followed the majority of these participants across the one year period. The study demonstrates the effectiveness of the Alexander technique, with and without exercise, in reducing disability score on a recognized scale.

A few points to consider:

• Instruction and education in the Alexander techniques involved a large number of trained professionals (152) and there may have been minor differences in the treatments given across the sample.
• The fact that the Alexander technique requires education by a registered professional does mean that referral is going to be affected by local care arrangements and resources across the country.
• Although the effectiveness was measured up to one year, longer follow-up would be valuable to assess longer-term outcomes and possible adverse effects.
• Assessments were by postal questionnaire and disability, quality of life and pain are highly subjective measures. How one person views their level of pain and disability is going to be different from another.
• All people in the groups had chronic back pain and fulfilled certain criteria. Many that the researchers contacted initially were not eligible for the study. Importantly, this study has no implications for care of acute low back pain.

Low back pain is a highly prevalent condition in the US with many adults suffering at some point in their lives, some of whom experience recurrent problems. It can also be highly disabling, cause significant work loss, and reduced quality of life for the individual. It is now well known that remaining active, rather than bed rest, is the best approach to back pain. However, there has been conflicting evidence on the effectiveness of posture or exercise education. These new findings are likely to promote further research into the benefits and possible limitations of the Alexander technique, the people for whom it would be most suitable, and the best approach to instructing sufferers.

If you’re thinking about trying the Alexander technique, it’s important to choose a teacher who’s experienced and qualified.

There aren’t currently any laws or regulations stating what training someone must have to teach the Alexander technique. Professional organizations offer courses (often for three years) and membership upon successful completion of the course.

Nutmeg essential oil

Nutmeg oil is a volatile essential oil from nutmeg (the seed of Myristica fragrans Houtt., family Myristicaceae) ¹⁾. At present, nutmeg still maintains its status as a unique kitchen spice with growing evidence for many of its traditional uses as a natural remedy. The evergreen nutmeg tree can reach 20 m in height and continues to be cultivated in its original location (Indonesian East Indies islands and Srilanka) as well as the West Indies (Caribbean Grenada islands) where the tree was introduced in the 19th century ²⁾. The lemon-like yellowish fruit contains the seed (nutmeg kernel, Figure 1) which is enveloped in a reddish net-like spongy tissue known as the aril or arillus (nutmeg mace, Figure 1). Both nutmeg kernel and nutmeg arillus are rich in essential oil that imparts the characteristic aroma and taste to nutmeg as a unique culinary ingredient. Primary metabolites (carbohydrates, lipids/fatty acids and proteins) constitute up to 80% of the weight of dry nutmeg kernel while the remaining weight comprises secondary metabolites of diverse chemical nature. They include essential oils (terpenes and phenylpropanoids) and phenolic compounds (caffeic, ferulic and protocatechuic acids, lignans/neolignans, and diarylalaknes) as the major constituents ³⁾. Polyphenols and pigments (catechins, epicatechins, falvonoids, and cyanidins) are also present (Table 1). Nutmeg mace is separately processed from nutmeg and has relatively less fats and carbohydrates.

Table 1. Relative chemical composition of nutmeg kernel and methods of preparation of major constituents 

Figure 1. Nutmeg fruit anatomy

Figure 2. Nutmeg kernel

Figure 3. Nutmeg oil

Chemistry of major secondary metabolites of nutmeg essential oil

The essential oil is obtained by the steam distillation of ground nutmeg and is used heavily in the perfumery and pharmaceutical industries. The nutmeg essential oil is used as a natural food flavoring in baked goods, syrups, beverage and sweets etc. Nutmeg essential oil replaces ground nutmeg as it leaves no particles in the food. The essential oil is also used in the cosmetic and pharmaceutical industries for instance in tooth paste and as a major ingredient in some cough syrups. In traditional medicine nutmeg and nutmeg oil were used for illnesses related to the nervous and digestive systems.

The essential oil constitutes up to 16% of nutmeg (w/w) and is rich in monoterpenes (approximately 90%) and phenylpropanoids ⁷⁾. A number of recent reports listed between 27–37 components present at various concentrations as determined by gas chromatography–mass spectrometry. In two independent studies by Wahab et al. ⁸⁾ and Piaru et al. ⁹⁾, the total number of compounds identified in the nutmeg essential oil was 37. In other studies, Du et al. ¹⁰⁾ reported 27 compounds, Muchtaridi and co-workers ¹¹⁾ listed 32 compounds while Piras et al. ¹²⁾ identified 30 compounds. Based on these most recent reports, the average number of compounds identified in nutmeg essential oil is 34. The monoterpenes -pinene (1, 7.4±3.5 %), 4-terpineol (2, 16.0±10.6 %), -terpinene (3, 5.3±3.3 %), limonene (4, 5.9±2.8 %), sabinene (5, 16.4±4.8 %), -terpineol (6, 2.4±2.2 %), -terpinene (7, 4.4±3.7 %), and -pinene (8, 5.2±3.0 %); and the phenylpropanoids myristicin (9, 12.4±11.7 %), elemicin (10, 1.9±1.7 %), methyleugenol (11, 3.8±7.2 %), safrole (12, 2.6±1.9 %), eugenol (13, 6.8±11.4 %), and methylisoeugenol (14, 5.7±9.6 %) were the most detected constituents in the five reported samples. Interestingly, isoeugenol the propenyl isomer of 13 or the O-demethyl isomer of 14, was present in trace amounts in only one of the five recent reports on the essential oil of nutmeg (Muchtaridi et al. 2010). Mean concentrations shown between parentheses reflects a wide range of variability (chemical structures are shown in Figure 2).

Table 1. Chemical composition of nutmeg essential oil from nutmeg seeds

Figure 4. Nutmeg essential oil major secondary metabolites – monoterpenes (90% approx.) and phenylpropanoids

Lignans and neolignans

Based on the number of identified compounds, lignans and neolignans constitute the most abundant class of secondary metabolites present in nutmeg kernel and mace ¹⁵⁾. A lignan can be loosely identified as a product of tail-to-tail dimerization of two phenylpropanoids while neolignans are formed mainly via head-to-tail coupling, with other possible non-C-2/C-2 couplings. Thus, the basic skeleton of a lignan usually comprises a dibenzyl-substituted tetrahydrofuran, a hexahydrofurofuran or a butane moiety while that of a neolignan may be an ether, a benzofuran, a benzodioxane, or a biphenyl (head-to-head coupling). Due to the abundance of phenylpropanoids (see Figure 4 above number 9-14) in nutmeg, all identified lignans and neolignans represent various dimerization patterns between these five phenylpropanoids.

Diphenylalkanes

In addition to lignans, which can be chemically classified as diphenylbutanes, two types of diphenylalkanes have been identified in nutmeg. The diphenylnonanoid malabaricones A-D were originally isolated Myristica malabarica (wild nutmeg), and, of these malabaricone B and C (59 & 60, respectively, Figure 5) are among common constituents later isolated from the kernel and mace of nutmeg as well as the bark of another Myristica species, Myristica cinnamomea (compound 60) ¹⁶⁾. Another -terpineol ether of malabaricone C (61) was isolated and reported as a new compound by Duan et al ¹⁷⁾. 1,3-Diphenylpropanes constitute a number of less common diphenylalkanes that were recently reported by Cuong et al. in the course of a bioassay-directed isolation project. Three compounds were isolated and identified as 5-¹⁸⁾. It is noteworthy that diarylpropanoids reported by Forrest et al. in 1974 ¹⁹⁾ are more appropriately classified as neolignans based on their benzofuranoid and 8,4’-oxyneolignan core structures.

Figure 5. Nutmeg essential oil major secondary metabolites – Diphenylalkanes

It seems that most promising biologically active secondary metabolites of nutmeg are either lignans/neolignans or diarylnonanoids.

The chemical groups, lignans and neolignans seem to be among the most studied. Nguyen et al. ²⁰⁾, in search of novel AMP-protein kinase (5’-adenosine monophosphate-activated protein kinase, AMPK) activators, isolated 2,5-bis-aryl-3,4-dimethyltetarhydrofuran lignans 15-20 & 22 from nutmeg. AMPK enzyme system plays a crucial role in regulating lipid and glucose homeostasis in a various tissue types. Studies have emphasized its role in obesity, diabetes, and cardiovascular diseases. Activation of AMPK has recently emerged as a therapeutic target for the aforementioned disease states ²¹⁾. Because of antihyperlipidemic and anti-atheroscelorotic activities reported for nutmeg extract ²²⁾, Nguyen et al. ²³⁾ screened the seed extract of AMPK activator activity, followed by isolation of pure lignan compounds. Out of the seven isolated compounds, tetrahydrofuroguaiacin, nectandrin A, and nectandrin B exerted strong activation of AMPK in differentiated C2C12 muscle cells, at 5 M concentration ²⁴⁾. The study also examined the effect of administration of a nectandrin B-rich active fraction in a high fat-induced animal model of obesity. The results showed a protective effect of the fraction against weight gain and blood glucose elevation caused by the high fat diet, suggesting potential application for nutmeg and its compounds in obesity, type 2 diabetes mellitus, and metabolic syndrome. A follow up study reported that nectandrin B activated AMPK in vascular smooth muscle cells and inhibited vascular smooth muscle cells proliferation and neointima formation, events that are critical in the development of vascular occlusive diseases. An elaborate study of the mechanism of vascular smooth muscle cells anti-proliferative effect revealed that AMPK activation resulted in P53 and P21 induction, that in turn downregulated retinoblastoma (Rb) phosphorylation, E2 transcription factor 1 (E2F1) resulting in inhibition of pin1 gene expression. The cascade of events results in inhibition of intimal hyperplasia ²⁵⁾. These results support a therapeutic potential for nectandrin B in the treatment or prevention of various occlusive vascular diseases, however further studies, particularly clinical studies are still needed.

Reviewing the literature reveals that lignans have received wide attention for their potential role in prevention of osteoporosis. Lignans are classified as phytoestrogens that exert estrogenic activity through binding to the estrogen receptor. Various phytoestrogens, especially isoflavones, have demonstrated beneficial clinical effects against bone loss in both preclinical and clinical studies ²⁶⁾. Machilin A, one of the lignan components of nutmeg, was reported to stimulate osteoblast differentiation through activation of the p38 mitogen activated protein kinase pathway ²⁷⁾. In early stage osteoblast differentiation, machilin A significantly increase alkaline phosphatase (ALP) activity, a commonly used marker for stimulating differentiation. Similarly, machilin A activated late stage differentiation and significant bone mineralization. The observed bone anabolic activity occurred in a dose-dependent manner. Other activities for machilin A include inhibition of proliferation of blood lymphocytes, human leukemia HL-60 cells, and topoisomerase I and II inhibition, suggesting potential anticancer properties ²⁸⁾. Follow-up studies and proper clinical evaluation of these properties remain uninvestigated.

Several pharmacological activities have been attributed to macelignan the main bioactive component identified in nutmeg mace. The activities range from anti-microbial, anti-inflammatory, anti-cancer, to antidiabetic, hepato- and neuro-protective ²⁹⁾. The anti-inflammatory effects of macelignan have been extensively studied. Shin et al. ³⁰⁾ reported that treatment with macelignan prevents the development of allergen-induced asthma in experimental animal models. The protective effect was coupled to a reduction in CD4+ T cells production of interleukin-4 (IL-4), but with no apparent effect on IL-17 or interferon-cells. Animals administered macelignan showed lower expression of the type-2 T helper cell (Th2) transcription factor, GATA3, an effect that needs might contribute to the protective anti-asthma activity, but requires further mechanistic studies. An earlier study demonstrated that macelignan inhibits the activation of mast cells in response to allergen exposure. Macelignan inhibited the release of histamine, calcium influx, degranulation, as well as various inflammatory mediators’ release ³¹⁾. The protective effect of macelignan has been tested in a variety of models of neurological dysfunction. Cui et al. ³²⁾ reported a protective effect of oral administration of macelignan against lipopolysaccharide-induced hippocampus microglial cells in rats. It also protected against impaired spatial learning induced by chronic lipopolysaccharide administration, implying potential therapeutic benefit for Alzheimer’s Disease patients. The mechanism of anti-inflammatory effect was investigated by Ma et al. ³³⁾. The study reported that macelignan suppressed lipopolysaccharide-induced activation of the Toll-like receptor 4 pathway, as evidenced by suppression of the nuclear factor NF-κB, reduction in cyclooxygenase type-2 (COX-2) expression, and inhibition of reactive oxygen species (ROS) generation. The results were in agreement with anti-inflammatory and protective effects of macelignan observed in animal models of diabetes and hepatotoxicity ³⁴⁾. A recent study corroborated the neuroprotective effect of macelignan. Using midbrain slice cultures, macelignan treatment protected dopaminergic neurons against the interferon (IFN)-γ and lipopolysaccharide-induced degeneration ³⁵⁾. Mechanistic studies revealed the protective neuroprotective effect observed was mediated by macelignan activation of the peroxisome proliferator activated receptor (PPAR-γ), which in turns activated arginase 1 enzyme expression. The result of the study implicates probable protective role of maceliganan against Parkinson’s Disease and other neurodegenerative disorders. The use of macelignan as an antiphotoaging agent stems from its antioxidant, antionflammtory, as well as its documented ability to protect human skin fibroblasts against damaging effects of UVB irradiation. The observed protective effect is mediated by suppression of two cellular responses involved in premature skin aging: the upregulation of matrix metalloproteinases and reduced collagen synthesis ³⁶⁾. Another potential skin application for macelignan was reported by Choi et al. ³⁷⁾ whereby the authors suggested the use of macelignan as a natural depigmenting agent based on its ability, at 10 M concentration, to inhibit melanosome transfer and dendrite formation in B16F10 melanoma cells. In addition to its earlier documented anti-diabetic effect, macelignan, isolated from Schisandra grandiflora, was recently reported to possess an inhibitory action against advanced glycation end products, an effect that adds to its potential role in the management of diabetes and metabolic syndrome ³⁸⁾.

Nutmeg essential oil uses and potential benefits

In folkloric medicine, nutmeg has long been used as a remedy for gastrointestinal problems, such as flatulence, colic, indigestion and diarrhea ³⁹⁾. The traditional use of nutmeg to treat tumors and infectious diseases, such as parasites and plague, has also been reported ⁴⁰⁾. Nutmeg has been used externally to treat skin infections, rheumatism and paralysis ⁴¹⁾. Other interesting uses for nutmeg include the treatment of psychological disorders ⁴²⁾, and as a cheap substitute for marijuana especially among teenagers, sailors and prison inmates ⁴³⁾.

Despite the myriad of folkloric uses of nutmeg, preclinical and clinical studies supporting such uses are relatively limited. Pharmacological studies have confirmed a few activities of nutmeg extracts, including antidiarrheal, antimicrobial, antioxidant, and different central nervous system (CNS) activities. Gorver et al. ⁴⁴⁾ examined the effects of crude nutmeg suspension, aqueous, as well as petroleum ether extracts in a variety of activities. The study ⁴⁵⁾ revealed a significant antidiarrheal effect exerted by both the crude suspension and petroleum ether nutmeg extract. However, only the petroleum ether extract had a significant sedative effect. None of the extracts showed significant cardiovascular effects as measured by blood pressure and ECG changes. On the other hand, a cardioprotective effect against myocardial infarction (heart attack) has been reported. Abdul Kareem et al. ⁴⁶⁾ examined the effect of daily administration of aqueous nutmeg extract (100 mg/kg, orally) for 30 days on isoproterenol-induced heart attack in adult male rats. Data collected show that pretreatment with nutmeg extract offered protection against isoproterenol effects on blood glucose, plasma lipids, as well as histological myocardiac changes, suggesting a potential cardiovascular protective role of nutmeg consumption.

Very few studies examined the antimicrobial activity of nutmeg extracts. Methanolic extracts possess potent antifungal activity against various plant pathogenic fungi, with three lignans (erythro-austrobailignan-6 [macelignan, 23], meso-dihydroguaiaretic acid [30] and nectandrin B [19]) identified as the primary constituents responsible for the reported antifungal activity ⁴⁷⁾. Similar antimicrobial activity was reported for nutmeg against the pathogenic Escherichia coli O157 and O111. The activity proved to be selective against the pathogenic versus the non-pathogenic E. coli strains ⁴⁸⁾. On the other hand, evaluation of nutmeg ethanolic extract against clinical isolates of Staphylococcus aureus, E. coli, and Streptococcus pyogenes resulted in lack of antimicrobial activity against all tested bacteria ⁴⁹⁾. Ethyl acetate and ethanolic extracts of the seed, mace, and flesh of nutmeg demonstrated high bactericidal activity against several Gram positive and Gram negative oral pathogens ⁵⁰⁾. In vitro evaluation of antimalarial activity of 27 herbal extracts and 5 formulations proved nutmeg to be among the identified eight extracts that exhibited potent antimalarial activity with IC50 value less than 10 mg/mL. In addition, the activity showed a selectivity index of >10 against multidrug resistant Plasmodium falciparum versus human renal epithelial cells ⁵¹⁾. Chemical investigation of nutmeg resulted in the isolation of a wide range of phenolic compounds belonging to the lignan group. With such compounds identified, research efforts intensified at evaluating the antioxidant potential of nutmeg. A study conducted by Assa et al. ⁵²⁾ examined the antioxidant capacity of methanolic extracts of nutmeg mace, seed, and flesh. Results attributed the highest free radical scavenging antioxidant activity to the seed extract based on the 1,1-diphneyl-2-picrylhydrazyl (DPPH) and ferric-reducing antioxidant power assays. Phytochemical evaluation correlated the high antioxidant capacity of the seed extract to its tannin, terpenoid, and flavonoid components. Lack of antioxidant activity of mace was also reported by Yadav and Bhatnagar ⁵³⁾ and was attributed to the relatively low polyphenolic content. The antioxidant properties of the aqueous extract of nutmeg seem to be responsible for its observed antimuatgenic and antimitotic actions against the cyclophosphamide-induced carcinogenic effects in the Allium cepa test ⁵⁴⁾.

Unlike the plethora of preclinical studies evaluating the nutmeg extracts, very few studies examined the potential activities of nutmeg oil. Wahab et al. ⁵⁵⁾ reported a dose-dependent activity of nutmeg oil in various animal seizure models. The oil exerted significant anticonvulsant effect against seizures induced by maximal electroshock, pentylenetetrazole, and strychnine, at doses that did not impair locomotor activity. Higher doses of the nutmeg essential oil seem to possess a weak proconvulsant effect, potentiating the clonic seizures induced by both pentylenetetrazole and bicuculline. Administration of nutmeg essential oil to experimental animals via the inhalation route showed a dose-dependent depressant effect on locomotor activity, with potential sedative effect attributed to myristicin, safrole, and 4-terpineol oil constituents ⁵⁶⁾. Using the DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging assay, Piaru et al. ⁵⁷⁾ reported a significant antioxidant activity of nutmeg oil. The oil also showed strong cytotoxic action against colorectal cancer carcinoma cell line and breast carcinoma cell line.

Limited studies focused on preclinical pharmacological evaluation of myristicin. Leiter et al. ⁵⁸⁾ examined the anxiolytic effect of myristicin (see Figure 4 above – phenylpropanoids of nutmeg essential oil – number 9) in the experimental elevated plus maze animal model. In line with a previous report by Sonvane and co-workers ⁵⁹⁾, myristicin failed to show anxiolytic action in the Leiter et al. study. The results demonstrated that myristicin may actually have some anxiogenic effect and may antagonize the actions of benzodiazepine, the GABAA receptors allosteric potentiators. In addition the CNS activity, antihelmintic ⁶⁰⁾, insecticidal ⁶¹⁾, apoptotic, and protection against DNA damage ⁶²⁾ effects were reported to myristicin ⁶³⁾. However, most of these activities are scattered in the literature, with no systematic follow up studies that further corroborate the findings or carry them further to application.

The most studied pharmacological activity attributed to nutmeg is its effects on the central nervous system (CNS). As early as the 12th century, nutmeg has been used and known for its central nervous system activity. Available literature has recognized a variety of nervous system effects of nutmeg and its major constituents. Earlier anecdotes report psychoactive and hallucinogenic properties of nutmeg ⁶⁴⁾. These reports were the basis of Shulgin’s hypothesis that attributed nutmeg’s psychoactivity to metabolic conversion of its main phenylpropanoid constituents to amphetamine-like metabolites ⁶⁵⁾. So far, the hypothesis has not been experimentally supported. Inconsistent animal findings and lack of detection of the amphetamine-like metabolites in biological fluids of nutmeg abusers led to reevaluation of the validity of the hypothesis ⁶⁶⁾. Further experimental data have ascribed several additional nervous system effects to nutmeg. Hayfaa et al. ⁶⁷⁾ reported analgesic activity of acidulated ethanolic extract of nutmeg (1 g/kg dose) in acetic acid-induced writhing animal model in support of earlier reports of the analgesic activity of the n-hexane nutmeg extract ⁶⁸⁾. Neurobehavioral effects exerted by nutmeg have been documented in various animal models, with numerous activities reported. Sonavane et al. ⁶⁹⁾ reported an anxiogenic activity exerted by the n-hexane extract of nutmeg, at doses of 10 and 30 mg/kg, i.p., as well by trimyristin (10, 30, and 100 mg/kg, intra-peritoneal). On the other hand, Ayurvedic literature reports the use of aqueous nutmeg extract as an anxiolytic agent ⁷⁰⁾. Such claim has not been substantiated by experimental dependent anxiolytic activity of aqueous nutmeg extract in the open field test experimental model. Similar to reported results for its effect on anxiety, conflicting data have been documented for nutmeg’s (and its components) effect on depression. Dhingra et al. ⁷¹⁾ and Moinuddin et al. ⁷²⁾ reported antidepressant activity of nutmeg extracts in both models of behavioral despair as well in reserpine reversal test paradigms, respectively. The studies also suggested the involvement of adrenergic, serotonergic, and dopaminergic systems in the observed antidepressant effect, since it was inhibited by 1 and dopaminergic receptor antagonists as well as a serotonin synthesis inhibitor. On the other hand, tryimyristin exerted a depressant effect when tested in behavioral despair animal models and potentiated hypothermia induced by reserpine. The observed effects were blocked by pre-administration of a serotonin 5-HT2A receptor antagonist ⁷³⁾. A previous study in a laboratory ⁷⁴⁾ evaluated the neurobehavioral effects of nutmeg in the four-point tetrad assay as compared to common drugs of abuse, Δ9-tetrahydrocannabinol (Δ9-THC), morphine, and amphetamine. The results of the study showed that nutmeg extracts have various activities in the assay, depending on the nature of the extract, as well as the route of administration. The study demonstrated that the dichloromethane nutmeg extract, when injected at 100 and 300 mg/kg doses, intra-peritoneal, exerted some cannabimimetic activity in the tetrad assay at ⁷⁵⁾.

Maity and co-workers reported a significant healing effect of malabaricone B against indomethacin-induced stomach ulcer ⁷⁶⁾. Administration of malabaricone B attenuated the increased nitric oxide synthesis induced by indomethacin, while enhancing the arginase pathway, thus favoring an anti / pro inflammatory cytokine ratio. Malabaricone C has potential pharmacological benefits in vascular disease ⁷⁷⁾, promotion of healing, anti-inflammation and angiogenesis caused by stomach ulcers ⁷⁸⁾, antioxidant activity ⁷⁹⁾ and cytotoxic activity against certain cancers ⁸⁰⁾. Malabaricone C also has anti-anaerobic, antifungal, and antibacterial properties ⁸¹⁾ as well as anti-parasitic, leishmanicidal and nematocidal activity ⁸²⁾.

For a long time studies have focused on lignans as the main active components of nutmeg. Recent research efforts explored the activities of neolignan-type compounds. Kang et al. reported an antiplatelet activity to erythro-(7S,8R)-7-acetoxy-3,4,3’,5’-tetramethoxy-8-O-4’-neolignan (EATN) ⁸³⁾. Results of the study showed that erythro-(7S,8R)-7-acetoxy-3,4,3’,5’-tetramethoxy-8-O-4’-neolignan (EATN), exerted a concentration dependent inhibition of platelet aggregation induced by platelet activating-factor and thrombin, and arachidonic acid. EATN had IC50 values of 3.2 ± 0.4 and 3.4 ± 0.4 M against platelet activating factor and thrombin-induced platelet aggregation, respectively. Further mechanistic investigation delineated the mechanism of anti-platelet activity. EATN regulates the level of cAMP, a crucial second messenger in the activation of platelet aggregation. EATN elevates intracellular cAMP levels inhibiting the Ca2+-induced mobilization of platelets activated by thrombin. Though these results are promising and elude to potential therapeutic application of EATN in atherothrombotic diseases, in vivo and clinical studies are still in demand. Licarin E, another neolignan, proved to protect against UVB irradiation damage to human skin fibroblasts ⁸⁴⁾. It reversed the two events induced by UVB: elevation of matrix metalloproteinase-1 and reduction of procollagen expression. The molecular mechanism of these effects proved to be via stimulation of transforming growth factor (TGF )/Smad signaling pathway. Similar to macelignan, licarin E could offer a novel therapeutic agent for photoaging. Using rat basophilic leukemia cells, stimulated by dinitrophenyl-human serum albumin, the effect of the neolignan licarin A on histamine release and mast cell activation was examined ⁸⁵⁾. The results demonstrated that licarin A inhibited mast cell activation, as evidenced by inhibiting tumor necrosis factor (TNF ), COX-2, and prostaglandin production. Further studies are needed to corroborate the role of licarin A in the treatment of immediate hypersensitivity cases. In vitro studies have elucidated that licarin A, isolated from Machilus thunbergii, may possess neuroprotective value against glutamate-induced toxicity of rat cortical cells ⁸⁶⁾. The protective effect was also evident against kainic acid-induced neurotoxicity, though more selective protection was observed for glutamate toxicity. The neuroprotective effect was attributed to the potent antioxidant properties of licarin A, evidenced by reduction of NO (nitric oxide), peroxide, free radical production as well as enhancing the activity of antioxidant enzyme systems. In addition, licarin A effectively suppressed Ca2+ influx that is typically induced by glutamate. Synthetic (−)-licarin A was reported to possess concentration-dependent anti-parasitic activity ⁸⁷⁾. In vitro studies reported potent inhibition of growth Leishmania promastigotes, suggesting promising application as a leishmanicidal agent. Using a tuberculosis murine animal model, Leon-Diaz et al. ⁸⁸⁾ demonstrated that licarin A possesses a significant suppressant action of the pulmonary burden and pneumonia in animals infected with both drug sensitive as well as drug-resistant tuberculosis strains. Animals administered licarin A (5mg/kg for 30 days) showed significant reduction in lung bacilli and pneumonia incidence. The anti-parasitic effect of licarin A was further corroborated against both Schistosoma mansoni and Trypanosoma cruzi ⁸⁹⁾. It is evident that the potential anti-parasitic activity of licarin A is worth further investigation in the hope of future development of effective medications.

Nutmeg essential oil side effects

Myristicin (see Figure 4 above – phenylpropanoids of nutmeg essential oil – number 9) is the major phenylpropanoid constituent of nutmeg essential oil. Various toxicological reports have attributed adverse effects associated with nutmeg ingestion to myristicin ⁹⁰⁾. These adverse effects include gastrointestinal; vomiting, and paralytic ileus, nervous system; drowsiness, paresthesia, numbness, reality detachment, and cardiovascular; hypotension, tachycardia, symptoms ⁹¹⁾, ⁹²⁾.

The central nervous system depressant effect of trimyristin, the main triglyceride constituent of nutmeg butter, was documented in mice ⁹³⁾. Trimyristin significantly increased immobility time in both forced swim and tail suspension murine tests, indicating a depressant-like action, when administered intraperitoneal injection (abdominal cavity injection) at 10 and 30 mg/kg doses. Furthermore the activity was inhibited by various antidepressant medications including the selective serotonin reuptake inhibitor fluoxetine, the tricyclic antidepressants imipramine, and the atypical antidepressant mianserin. However, the mechanism of such depressant action remains unclear.

Summary of nutmeg essential oil uses and benefits

Nutmeg kernel and mace have a long history of use as a spice and traditional remedy that goes back to the 12th century. Traditional uses of nutmeg in alleviating gastrointestinal disorders, managing rheumatic pain, healing skin wounds and infections as well as its use as a calming agent resulted in massive contemporary efforts to evaluate its different extracts, fractions. Despite the traditional uses and activities reported for nutmeg, the mechanisms underlying its effects remain unclear and further pharmacological studies are certainly needed to properly assess the therapeutic potential of this natural product ⁹⁴⁾, ⁹⁵⁾.

One of the most commonly evaluated activities of nutmeg essential oil and extracts is their effect on the CNS. In addition to the essential oil which is rich in terpenes and phenylpropanoids, nutmeg has significant levels of non-volatile secondary metabolites of the lignan/neolignan-type as well as diarylalkanes that have been isolated and identified. Preclinical studies to evaluate such compounds as myristicin, macelignan, nectandrin A & B, licarin A-E, and malabaricone B & C are abundant in recent literature with focus on anxiolytic, antioxidant/chemopreventive, anti-inflammatory, anti-infective effects of individual compounds. On the other hand, clinical trials are not as abundant in the current literature. They are limited in size, design and focus (topical application of nutmeg or use of a mixed herbal product containing nutmeg among other extracts) with no individual pure compounds included.

While phytochemical studies have supported some of the folkloric uses of nutmeg, very few clinical studies systematically investigated the clinical efficacy of nutmeg uses. A thorough literature search revealed merely two small clinical studies. A randomized, placebo-controlled, double blind trial examined the clinical effects of using topical nutmeg extract in patients with painful diabetic neuropathy ⁹⁶⁾. The study included 74 diabetic neuropathy patients (males and females, ages 30–85 years) who were randomized to receive the different topical treatment: nutmeg extract, mace oil, nutmeg oil, coconut oil, methyl salicylate, menthol, or placebo. The study used a validated Brief Pain Inventory that has been modified for painful diabetic neuropathy in addition to the Neuropathic Pain Symptom Inventory. Following four weeks of treatment, patients showed within group significant improvement of pain, mood scores, and daily functions. However no statistically significant effect was reported between the nutmeg treated and placebo groups. Being the only study that assessed the clinical analgesic effect of nutmeg, it is hard to draw conclusions because of the study limitations. The small sample size, short duration of the study, lack of inert placebo, poor patient compliance, and use of non-standardized nutmeg preparations are all limitations that hinder proper evaluation of the therapeutic role of nutmeg in pain disorders. The other study retrieved describes an open, uncontrolled trial that examined the effect of administration of a nutmeg-containing herbal product in a total of 251 patients ⁹⁷⁾. The product used, Revivin, contained a mixture of various plant extracts including nutmeg in addition to carbohydrate molecules, and is commonly used to enhance performance, improve appetite, and reduce weakness and fatigue. Patients (average age 44 years, males and females) received the capsule daily for 4 weeks. Outcomes were assessed by self-filled patients’ questionnaire. Patients reported improvement in mood, insomnia, and overall weakness, and no adverse effects were reported by the patient. The study suffers from several limitations: subjectivity of outcome evaluation, short duration, and lack of placebo control. In addition, since the study used a product where nutmeg constituted only one component of the mixture, the clinical nutmeg effect cannot be isolated. As evident, there is a lack of well-designed controlled clinical trials that evaluate the potential therapeutic place of nutmeg and its components.

What is frankincense oil

Frankincense essential oil is prepared by the steam distillation of frankincense gum resin (olibanum) is one of the most commonly used essential oils in aromatherapy. Frankincense is an aromatic resin hardened from exuded gums obtained from trees of the genus Boswellia (Burseraceae family). Boswellia species includes Boswellia sacra from Oman and Yemen, Boswellia carteri from Somalia, and Boswellia serrata from India and China ¹⁾. The frankincense gum resin (olibanum) has been used in incense and fumigants, as well as a fixative in perfumes. Aroma from these resins is valued for its superior qualities for religious rituals since the time of ancient Egyptians ²⁾. Boswellia species resins have also been considered throughout the ages to have a wealth of healing properties. Considerable amount of work has been attempted to identify chemical compositions of frankincense essential oils from different commercial brands. Chemical constituents of frankincense essential oils differ significantly due to climates, time of harvest, storage conditions, geographical sources of resins ³⁾, and methods of preparations. The frankincense essential oil has been demonstrated in test tube studies to modulate critical biological activities including anti-rheumatism, anti-inflammatory ⁴⁾, antibacterial, antifungal and anticancer activities ⁵⁾. Boswellic acids from frankincense gum resins have been suggested to be a major compound in mediating various biological functions including anti-inflammatory and anti-cancer activities. Chevrier et al. ⁶⁾ reported that ethanol extracts of Boswellia carteri gum resins comprise 7 boswellic acids. Akihisa et al. ⁷⁾ reported that methanol extracts of Boswellia carteri resins consist of 15 triterpene acids including boswellic acids. Acetyl-11-keto-β-boswellic acid (AKBA) provides protective effects in a chemically induced mouse ulcerative colitis model ⁸⁾. It has been shown that β-boswellic acids from methanol extracts of Boswellia cateri gum resins exhibit potent cytotoxic activities against human neuroblastoma cell lines, IMR-32, NB-39, and SK-N-SH ⁹⁾. Shao et al. ¹⁰⁾ compared 4 triterpene acids including β-boswellic acid, 3-O-acetyl-β-boswellic acid and acetyl-11-keto-β-boswellic acid (AKBA) isolated from Boswellia serrata gum resins for their anti-cancer activity in vitro. Acetyl-11-keto-β-boswellic acid (AKBA) is the most pronounced inhibitory effects among the 4 triterpene acids in suppressing human leukemia HL-60 cell growth as well as DNA, RNA, and protein synthesis ¹¹⁾. AKBA also exhibits anti-proliferative and pro-apoptotic activities against human prostate cancer LNCaP and PC-3 cells in vitro and in animal models ¹²⁾, and induces cytotoxicity in human meningioma cells in culture ¹³⁾. Acetyl-11-keto-β-boswellic acid (AKBA) have also been proposed to provide anti-neoploastic activity through their anti-proliferative and pro-apoptotic properties in multiple human cancer cell lines including hepatoma cells ¹⁴⁾, melanoma cells ¹⁵⁾, fibrosarcoma cells ¹⁶⁾, colon cancer cells ¹⁷⁾, pancreatic cancer cells ¹⁸⁾ and prostate cancer cells ¹⁹⁾. Moreover, boswellic acids may not be the only compounds in frankincense essential oil for inducing pancreatic cancer cell death. Total boswellic acids contents were not proportionally related to essential oil-induced tumor cell cytotoxicity among different fractions. Additionally, frankincense hydrosol, the aqueous distillate of hydrodistilled Boswellia sacra gum resins, contained 0.0 to 15.5% boswellic acids, but did not have detectible cytoxicity against tumor cells even when a 1:5 dilution was added to the cultures. Tirucallic acids purified from Boswellia carteri gum resins have been shown to induce human prostate cancer cells death ²⁰⁾. Some researchers also observed that frankincense essential oil enriched with high molecular weight compounds but lower boswellic acids contents frankincense essential oil was much more potent at inducing cytotoxicity in cultured pancreatic cancer cells.

Higher boswellic acids contents are present in frankincense essential oil hydrodistilled at higher temperature. A study by Hostanska et al. ²¹⁾ reported that components other than AKBA from solvent extracts of Boswellia serrata gum resins can induce cytotoxicity in malignant cells. Additionally, Estrada et al. ²²⁾ reported that tirucallic acids purified from Boswellia carteri gum resins induce apoptosis in human prostate cancer cell lines. Although the active compound(s) in Boswellia sacra frankincense essential oil responsible for anti-tumor activity cannot be identified immediately due the complexity of frankincense essential oils, chemical compositions and/or ratios of these components present in the oil obtained at 100 °C (212 °F) would play significant roles in tumor cell-specific cytotoxicity.

Frankincense essential oil-regulated cell cycle regulators and signaling pathways were compared to boswellia acids-activated pathways in a variety of cancer cell lines. It has been reported that boswellic acids can regulate tumor cell viability by activating a variety of mechanisms. Acetyl-keto-beta-boswellic acid (AKBA) arrests cancer cells at the G1 phase of cell cycle, suppresses levels of cyclin D1 and E, cdk 2 and 4, and Rb phosphorylation, as well as increases expression of p21 through a p53-independent pathway ²³⁾. Acetyl-keto-beta-boswellic acid (AKBA) activates death receptor-5 through elevated expression of CATT/enhancer binding protein homologus protein in human prostate cancer LNCaP and PC-3 cells ²⁴⁾. Boswellic acids including AKBA strongly induce apoptosis through activation of caspase-3, -8, and −9 and cleavages of PARP in colon cancer HT29 cells and hepatoma HepG2 cells ²⁵⁾. In addition, AKBA inhibits topoisomerases I and II without inhibiting DNA fragmentation in glioma and leukemia HL-60 cells ²⁶⁾.

Boswellia sacra essential oil also suppresses important malignant features of tumor cells, such as invasion and multicellular tumor spheroids growth. Tumor cell plasticity enables highly malignant tumor cells to express endothelial cell-specific markers and form vessel-like network structures on basement membranes. The in vitro Matrigel-based tumor invasion model has been shown to correlate with in vivo metastatic potential ²⁷⁾. This in vitro model has been used to study mechanisms of cancer aggressive behavior, metastasis, and poor prognosis ²⁸⁾, and has been used as a tool to screen therapeutic agents for their anti-metastatic property ²⁹⁾. Boswellia sacra frankincense essential oil obtained at 100 °C (212 °F) is more potent than essential oil obtained at 78 °C hydrodistillation in disruption cellular networks on Matrigel and spheroids. More importantly, observations obtained in the above described experimental models are consistent with clinical responses in human cancer cases. These results suggest that Boswellia sacra frankincense essential oil may represent an effective therapeutic agent for treating invasive breast cancer. The anti-tumor activity of frankincense essential oil is mediated through multiple signaling pathways and cell cycle regulators. To further confirm these anti-cancer and other therapeutic activities of frankincense essential oil and frankincense resin extracts which are derived from animal and test tube studies, human clinical studies are required to support their uses in human diseases. Currently, a Boswellia serrata extracts is undergoing a phase I trial to study how well Boswellia serrata extract works in treating patients with ductal breast carcinoma in situ, stage I-III breast cancer, or stage I-III colon cancer that are undergoing surgery ³⁰⁾.

Frankincense essential oil uses and benefits

In traditional Chinese medicine, frankincense from Boswellia carterii is commonly used for topical treatment of pain and inflammation ³¹⁾. A study carried out to investigate the antinociceptive and anti-inflammatory action of frankincense oil and water extracts and three of its main componentes, i.e., linalool, α-pinene and 1-octanol, via xylene-induced ear edema and a formalin-inflamed hindpaw model in male Kunming mice, showed consistent evidence about their anti-inflammatory and analgesic effects. Frankincense oil extract, which contains more linalool, α-pinene and 1-octanol than frankincense water extract, produced a faster and more effective reduction of the swelling and pain than the water extract ³²⁾. In addition, the combination of linalool, α-pinene and 1-octanol exhibited stronger biological effect on hindpaw inflammation and cyclooxygenase-2 (COX-2) overexpression than the three compounds used separately, indicating that they contribute to the topical antinociceptive and anti-inflammatory properties of frankincense by inhibiting cyclooxygenase-2 (COX-2) activation ³³⁾. For example, resins of Boswellia species have been used for the treatment of rheumatoid arthritis and other inflammatory diseases ³⁴⁾ such as Crohn’s disease ³⁵⁾. The anti-inflammatory activity has been attributed to the frankincense gum resin’s ability in regulating immune cytokine production ³⁶⁾ and leukocyte infiltration ³⁷⁾.

In a well conducted systematic study by Cochrane researchers ³⁸⁾ comparing Boswellia serrata extract, bismuth subsalicylate (Pepto-Bismol®), mesalamine, cholestyramine, probiotics, prednisolone and budesonide therapy in collagenous colitis – a type of microscopic colitis, a condition characterized by chronic watery non-bloody diarrhea. People with collagenous colitis have a normal appearing bowel when assessed by an endoscope (a camera used to look at the bowel); but have microscopic inflammation of the bowel when assessed by a biopsy (a tissue sample taken during endoscopy). The cause of this disorder is unknown. Budesonide is an immunosuppressive steroid drug that is quickly metabolized by the liver resulting in reduced steroid-related side-effects. Prednisolone is a steroid drug used to treat inflammation. Mesalamine (also known as 5-ASA) is an anti-inflammatory drug. Cholestyramine is a drug that helps the body remove bile acids. Pepto-Bismol®, is an antacid medication used to treat discomforts of the stomach and gastrointestinal tract. Probiotics are found in yogurt or dietary supplements and contain potentially beneficial bacteria or yeast. The researchers investigated whether these treatments improve symptoms (e.g. diarrhea) or microscopic inflammation of collagenous colitis and whether any side effects (harms) result from treatment. The outcome of that Cochrane review ³⁹⁾ was there is a low quality evidence suggesting that budesonide may be effective for inducing and maintaining clinical and histological response in patients with collagenous colitis. Furthermore, due to small sample sizes and low study quality, the study authros were uncertain about the benefits and harms of therapy with Pepto-Bismol®, Boswellia serrata extract, mesalamine with or without cholestramine, prednisolone and probiotics. These agents and other therapies require further study.

Madisch 2007 ⁴⁰⁾ completed a randomized, placebo-controlled, double-blind study at multiple German centers to evaluate the clinical response of Boswellia serrata extract on patients with collagenous colitis compared to placebo over 6 weeks. Thirty-one patients (aged 18 to 80 years) with clinically and histologically confirmed collagenous colitis (“at least five liquid or soft stools per day on average per week, and a complete colonoscopy performed within the last 4 weeks before randomization”) were randomized to receive Boswellia serrata extract (three 400 mg/day; n = 16) or identically matched placebo (n = 15). Patients were excluded in they had received budesonide, salicylates, steroids, prokinetics, antibiotics, ketoconazole, or non-steroidal anti-inflammatory drugs within four weeks of randomization or if they had other endoscopically or histologically verified causes for diarrhea, infectious diarrhea, previous colonic surgery, or known intolerance to Boswellia serrata extract or were pregnant or lactating. The primary endpoint was clinical remission after 6 weeks (stool frequency of < 3 per day); secondary outcomes included histological improvements and quality of life measures. “Patients who did not respond to treatment after 6 weeks were individually unblinded. If they were in the active treatment group, they were judged as treatment failure. If they were in the placebo group, crossover therapy with open-labelled Boswellia serrata extract 400 mg, given orally three times daily was offered.” Intention to treat analysis demonstrated no significant effect of Boswellia serrata extract compared to placebo on achieving clinical remission, 43.8% vs 26.7%, respectively) ⁴¹⁾. In Madisch 2007 ⁴²⁾, there was a slight reduction in the thickness of the subepithelial collagen band and inflammation score in both the Boswellia serrata and placebo groups at the end of 6 weeks of therapy, but no difference compared to baseline or between the groups. At the end of 6 weeks of therapy, there were no significant changes in quality of life scores in either the Boswellia serrata or placebo groups compared to baseline or between groups ⁴³⁾.

In another 2014 Cochrane review ⁴⁴⁾ involving oral herbal therapies for treating osteoarthritis. Thirty-three different medicinal plant products were compared with placebo or active intervention controls and many comparisons had single studies only; the authors have restricted reporting of results to multiple studies of Boswellia serrata (monoherbal) and avocado-soyabean unsaponifiables (ASU) (two herb combination) products. The authors’ conclusions were there was evidence for the proprietary avocado-soyabean unsaponifiables (ASU) product Piasclidine® in the treatment of osteoarthritis symptoms seems moderate for short term use, but studies over a longer term and against an apparently active control are less convincing. Several other medicinal plant products, including extracts of Boswellia serrata, have moderate-quality evidence for trends of benefits that warrant further investigation in light of the fact that the risk of adverse events appear low ⁴⁵⁾.

There is no evidence that Piasclidine® significantly improves joint structure, and limited evidence that it prevents joint space narrowing. Structural changes were not tested for with any other herbal intervention ⁴⁶⁾.

Further investigations are required to determine optimum daily doses producing clinical benefits without adverse events ⁴⁷⁾.

Key results of the oral herbal therapies for treating osteoarthritis ⁴⁸⁾:

Boswellia serrata

Pain on a scale of 0 to 100 points (lower scores mean reduced pain):

• people who used 100 mg of enriched Boswellia serrata extract rated their pain 17 points lower (range 8 to 26 points lower) (17% absolute improvement) at 90 days compared with placebo;
• people who used enriched Boswellia serrata extract 100 mg rated their pain as 23 points;
• people who used a placebo preparation rated their pain as 40 points.

Physical function on a scale of 0 to 100 points (lower scores means better physical function):

• people who used 100 mg of enriched Boswellia serrata extract rated their physical function 8 points better (2 to 14 points better) on a 100 point scale (8% absolute improvement) at 90 days compared with placebo;
• people who used 100 mg of enriched Boswellia serrata extract rated their physical function as 25 points;
• people who used placebo rated their physical function as 33 points.

Avocado-soyabean unsaponifiables (ASU) product Piascledine®

Pain on a scale of 0 to 100 points (lower scores mean less pain):

• people who used avocado-soyabean unsaponifiables 300 mg rated their pain 8 points lower (1 to 16 points lower) on a 100 point scale (8% absolute improvement) at 3 to 12 months compared with placebo;
• people who used avocado-soyabean unsaponifiables 300 mg rated their pain as 33 points;
• people who used placebo rated their pain as 41 points.

Physical function on a scale of 0 to 100 mm scale (lower scores means better physical function):

• people who used avocado-soyabean unsaponifiables 300 mg rated their physical function 7 mm better (2 to 12 mm better) on a 100 mm scale (7% absolute improvement) at 3 to 12 months compared with placebo;
• people who used avocado-soyabean unsaponifiables 300 mg rated their physical function as 40 mm;
• people who used placebo rated their physical function as 47 mm.

Summary and quality of the evidence

There is moderate-quality evidence that in people with osteoarthritis Boswellia serrata slightly improved pain and function. Further research may change the estimates.

There is moderate-quality evidence that avocado-soybean unsaponifiables (ASU) probably improved pain and function slightly, but may not preserve joint space. Further research may change the estimates.

The study authors were uncertain whether other oral herbal products improve osteoarthritis pain or function, or slow progression of joint structure damage because the available evidence is limited to single studies or studies that cannot be pooled, and some of these studies are of low to very low quality. Quality of life was not measured.

Herbal therapies may cause side effects, however they were uncertain if there is an increased risk of these.

Figure 1. Frankincense gum resin

Figure 2. Frankincense essential oil

Frankincense oil side effects

There is only little published material as far as side effects are concerned. In the clinical trials described in this study ⁴⁹⁾, two out of 40 patients who received frankincense gum resin of 300 mg three times daily over a period of 6 weeks complained about epigastric pain, hyperacidity and nausea ⁵⁰⁾. In the study dealing with ulcerative colitis ⁵¹⁾, 6 out of 34 patients complained about retrosternal burning, nausea, fullness of abdomen, epigastric pain and anorexia. In a study reported by Böker et al. ⁵²⁾, some patients developed nausea and vomiting, in two patients skin irritations have also been observed. The side effects were reversible after omission of the treatment. In the study of Streffer et al. ⁵³⁾, some gastrointestinal symptoms were observed.

In a retrospective analysis in 2000, the laboratory parameters before and after treatment of patients suffering from rheumatoid arthritis, ulcerative colitis, Crohn’s disease, neurodermitis, lupus erythematosus, multiple sclerosis, astrocytoma, glioblastoma, bronchial asthma and psoriasis and receiving the Boswellia preparation H15TM over a period of 6 years before and after treatment were tested. No significant changes related to the therapy were observed ⁵⁴⁾.

In Madisch 2007 ⁵⁵⁾ randomized, placebo-controlled, double-blind study at multiple German centers to evaluate the clinical response of Boswellia serrata extract on patients with collagenous colitis compared to placebo over 6 weeks, 12.5% (2/16) of patients treated with Boswellia serrata extract reported an adverse event. Of these, 1 patient withdrew from the trial due to hypoglycemia, dizziness and anorexia. The other developed bacterial enteritis but completed the trial. One of 15 patients (7%) in the placebo group reported an adverse event (eczema and Coxsackie virus infection), but completed the trial. There was no significant different between the groups in adverse events or withdrawals due to adverse events. Twelve per cent (2/16) of patients treated with Boswellia serrata extract had an adverse event compared to 7% (1/15) of patients treated with placebo. Six (1/16) of patients treated with Boswellia serrata extract withdrew due to an adverse event compared to 0% (0/15) of patients treated with placebo. None of the adverse events were considered serious.

What is neroli

Neroli (Citrus aurantium L. var. amara) is also called Bitter orange, Seville orange, Sour orange, Bigarade orange or Marmalade orange, refers to a citrus tree (Citrus × aurantium) and its fruit ¹⁾. Neroli (Citrus aurantium) which is native to eastern Africa and tropical Asia is now grown throughout the Mediterranean region and elsewhere, including California and Florida. The main constituents of Neroli orange peel are the volatile oil and an amorphous, bitter glucoside called aurantiamarin. Other constituents include hesperidin, a colorless, tasteless, crystalline glucoside occurring mainlyin the white zest of the peel, isohesperidin, hesperic acid, aurantiamaric acid, and a bitter acrid resin. In the peel of immature fruits, the chief constituents are naringin and hesperidin, while in the fruit flesh it is umbelliferone. p-Octopamine and p-synephrine, both adrenergic agonists, are the most frequently mentioned biogenic amines found in bitter orange peel and other Citrus aurantium preparations and other species such as Citrus reticulata Blanco (mandarin orange). Many varieties of Neroli are used for their essential oil and are found in perfume, used as a flavoring in foods and beverages or as a solvent. The Seville orange variety is used in the production of marmalade.

• Neroli has been used in traditional Chinese and Japanese herbal medicines and by indigenous people of the Amazon rainforest for constipation. Amazonian natives also used it for nausea and indigestion.
• Different preparations made from Neroli (Citrus aurantium L. var. amara) blossoms are commonly used in ethnobotanical practices for the treatment of pain and inflammation in Iran ²⁾.
• Today, people use various Neroli products as a dietary supplement for heartburn, loss of appetite, nasal congestion, and weight loss. It is also applied to the skin for pain, bruises, and bed sores.
• Neroli, used in some weight-loss products, contains synephrine (see Figure 3) ³⁾, which is similar to the main chemical in the herb ephedra. Ephedra is banned by the U.S. Food and Drug Administration because it raises blood pressure and is linked to heart attack and stroke ⁴⁾.
• The National Collegiate Athletic Association (NCAA) placed synephrine (bitter orange) on its current list of banned drugs.
• The fruit, peel, flower, and oil are used and can be taken by mouth in tablets and capsules. Bitter orange oil can be applied to the skin.

Neroli (bitter oranges) are grown mainly for processing as preserves (especially, marmalade) and syrup due to their tart flavor. The essential oil is used to add fragrance to beverages and liqueurs (e.g., Curacao and Grand Marnier), sweet foods like candies and cakes, soaps, detergents, cosmetics, perfumes, and in sauces for meats and poultry. Neroli orange peel is used in many pharmacopoeial preparations as a flavoring agent, stomachic (assisting digestion) and carminative (relieving flatulence). Additionally, Neroli (bitter oranges) is reported to be an expectorant, laxative, hypertensive, nervine, tonic, and diuretic. The extract has been added to many dietary supplements and herbal weight loss formulas (as an alternative to ephedra). Synephrine is the “active” ingredient of bitter orange and functions as a stimulant. It is also used as a vasoconstrictor in circulatory failure. Octopamine is used as a cardiotonic and to treat hypotension.

Exposure to Neroli (bitter oranges) peel and its constituents occurs primarily via ingestion of the fruit itself or its products (e.g., orange juice, marmalade, flavorings and fragrances, and dietary supplements). Weight loss formulas usually contain 100-200 mg bitter orange extract, which provides 10-40 mg synephrine per dose. Extracts can contain up to 95% synephrine. Exposure can also result from peel oil used in aromatherapy and flavoring.

Figure 1. Neroli (bitter orange)

Figure 2. Neroli orange blossom  

Neroli extract and human clinical studies

Neroli (Bitter orange) peel and its constituent synephrine are present in dietary supplements with and without ephedra (ma huang) for weight loss. Synephrine and other Neroli (Bitter orange) biogenic amine constituents—octopamine, N-methyltyramine, tyramine, and hordenine—have adrenergic activity and may result in cardiovascular or other adverse effects similar to those induced by ephedra alkaloids ⁵⁾.

Neroli (bitter orange) is regulated by the U.S. Food and Drug Administration (FDA) ⁶⁾; the peel, oil, extracts, and oleoresins are Generally Recognized as Safe as a direct additive to food ⁷⁾. The peel is used in many pharmacopoeial preparations for flavoring and treatment of digestive problems. Oils from the fruit, peel, and other plant parts are also used for flavoring and fragrance and do not contain alkaloids. p-Octopamine and p-synephrine, the most frequently mentioned biogenic amines found in bitter orange extract, are agonists for both a- and b-adrenoceptors (octopamine has weak b-adrenergic activity) ⁸⁾. Octopamine is used as a cardiotonic and to treat hypotension. Synephrine is used as a vasoconstrictor in circulatory failure. Extracts used in many dietary supplements and herbal weight-loss formulas as an alternative to ephedra have concentrations of the sympathomimetic alkaloid synephrine that are often much higher than the synephrine concentrations reported for traditional extracts of the dried fruit or peel.

Uncertainty has existed concerning the safety of Neroli (bitter orange) extract and p-synephrine. In general, there are the p-synephrine which is a phenylethylamine derivative that has the hydroxy group in the para position on the benzene ring and the synthetic m-synephrine (phenylephrine) which has a hydroxyl group in the meta position on the benzene ring) (Figures 3 and 4). m-Synephrine exhibits cardiovascular effects but is not a constituent of Neroli (bitter orange) ⁹⁾, ¹⁰⁾. Properties possessed by m-synephrine are inappropriately attributed to Neroli (bitter orange) extract and p-synephrine, and clinical case study reports and reviews involving bitter orange extract frequently make inappropriate references to m-synpephrine ¹¹⁾.

Concentrations of octopamine in extracts are less than those reported for synephrine. Weight loss formulas usually contain 100-200 mg bitter orange extract, which provides 10-40 mg synephrine per dose. Health concerns about bitter orange and other compounds in dietary supplements led to the FDA’s collection of product labels for the Center for Food Safety and Applied Nutrition to evaluate possible health risks. Concentrations of synephrine measured in several dietary  products were generally lower than that declared on the label.

Following intraveous administration of synephrine to patients, ~66 and 10% of the administered dose was recovered in the urine as deaminated p-hydroxymandelic acid and unchanged synephrine, respectively (2.5% of the dose was recovered as unchanged synephrine following ingestion). Trace amounts of p- and m-octopamine and p- and m-synephrine were found in plasma and platelets of healthy human subjects. Low concentrations of octopamine, thought to be a metabolic byproduct of catecholamine biosynthesis, are present in the central nervous system and peripheral tissues of vertebrates. Oral exposure of mice to extracts of Neroli (bitter orange) peel suppressed cell viability of splenocytes and thymocytes. Oral exposure of rats to aqueous extracts of the immature fruit caused decreased food intake and body weight gain, ventricular arrhythmias, and inhibited Type I allergic reactions. Synephrine affected the sense organs and caused convulsions, dyspnea, cyanosis, and respiratory stimulation in other animal studies. Octopamine and synephrine were not mutagenic in Aspergillus nidulans diploid strains or L5178Y mouse lymphoma cells, respectively.

Pharmacologically, synephrine is similar to ephedrine but does not have its central nervous system (CNS) effects ¹²⁾. Ephedrine is a plant derivative that agonizes α- and β-adrenergic receptors ¹³⁾ in the heart and blood vessels, causing peripheral vasoconstriction and increased heart rate. This can have dramatic functional effects on the heart, because increased afterload and heart rate result not only in greater myocardial oxygen demand but in decreased diastolic filling and supply of oxygen to myocytes. Synephrine is therefore being considered as an alternate for ephedrine in dietary supplements ¹⁴⁾. Synephrine and N-methyltyrosamine (chemicals found in immature C. aurantium fruit) have been shown to be effective antishock (i.e., primarily cardiotonic and vasoconstrictive) agents. In one study, 48 of 50 children with infective shock were cured when treated with synthetic synephrine and N-methyltyrosamine (1.66 to 24 mg/kg).

Case reports do exist of ischemic cerebrovascular accident, myocardial infarction, and unremitting tachycardia in association with synephrine use, but confounding factors exist in many of these reports ¹⁵⁾, ¹⁶⁾. The Canadian Health Department reports that, from 1 January 1998 through 28 February 2004, it received 16 reports of adverse cardiovascular events—including tachycardia, cardiac arrest, ventricular fibrillation, and syncope—in suspected association with the use of products containing bitter orange or synephrine ¹⁷⁾. Products containing synephrine and that are promoted for weight loss are not authorized for sale in Canada.

Octopamine is used in Chinese medicine as a cardiotonic and to treat hypotension. The natural D(-) form is more potent that the L(+) form in producing cardiovascular adrenergic responses. In some invertebrates, it can also serve as a neurotransmitter.

Several human safety and efficacy studies have been conducted on bitter orange extract (p-synephrine) alone. However results involving both published and unpublished clinical studies indicate that p-synephrine alone or in combination with caffeine does not appear to produce significant adverse cardiovascular effects or pose a risk to human health at doses commonly ingested orally ¹⁸⁾. No adverse effects have been directly attributable to bitter orange extract or p-synephrine ¹⁹⁾. p-Synephrine/bitter orange extract alone as well as in combination with other ingredients results in significant increases in resting metabolic rate, and when taken for periods of time up to 12 weeks may result in modest weight loss ²⁰⁾.

The results indicate that bitter orange extract and p-synephrine increase metabolism and energy expenditure ²¹⁾. The data accumulated to date do not support hypothesized concerns regarding potential adverse effects of p-synephrine particularly with respect to the cardiovascular system due to a paucity of binding to α-, β-1 and β-2 adrenergic receptors while exhibiting modest binding to β-3 adrenergic receptors ²²⁾. However, a need exists for additional well controlled, long term human efficacy and safety studies involving p-synephrine/bitter orange extract.

Figure 3. Chemical structure of p-Synephrine

Figure 4. Chemical structure of m-Synephrine

[Source ²⁴⁾]

Neroli essential oil

Neroli oil is an essential oil produced from the blossom of Neroli or the Citrus aurantium blossom. The bitter orange blossom is the fragrant flower of Neroli (bitter orange tree). Its scent is sweet, honeyed and somewhat metallic with green and spicy facets. The bitter orange blossom oil and extracts are extensively used in perfumery. Neroli orange blossom can be described as smelling sweeter, warmer and more floral than neroli (the bitter orange fruit). The difference between how neroli and orange blossom smell and why they are referred to with different names, is a result of the process of extraction that is used to obtain the oil from the blooms. Neroli is extracted by steam distillation and orange blossom is extracted via a process of enfleurage.

Enfleurage is a process that uses odorless fats that are solid at room temperature to capture the fragrant compounds exuded by plants. The process can be “cold” enfleurage or “hot” enfleurage.

• In cold enfleurage, a large framed plate of glass, called a chassis, is smeared with a layer of animal fat, usually lard or tallow (from pork or beef, respectively), and allowed to set. Botanical matter, usually petals or whole flowers, is then placed on the fat and its scent is allowed to diffuse into the fat over the course of 1-3 days. The process is then repeated by replacing the spent botanicals with fresh ones until the fat has reached a desired degree of fragrance saturation. This procedure was developed in southern France in the 18th century for the production of high-grade concentrates.

• In hot enfleurage, solid fats are heated and botanical matter is stirred into the fat. Spent botanicals are repeatedly strained from the fat and replaced with fresh material until the fat is saturated with fragrance. This method is considered the oldest known procedure for preserving plant fragrance substances.

However, the enfleurage method of fragrance extraction is now superseded by more efficient techniques such as solvent extraction or supercritical fluid extraction using liquid carbon dioxide (CO2) or similar compressed gases.

Neroli essential oil benefits

Neroli was analyzed by gas chromatography–mass spectrometry and twenty three constituents, representing 91.0 % of neroli oil were identified. The major components of neroli were characterized as linalool (28.5%), linalyl acetate (19.6%), nerolidol (9.1%) E,E-farnesol (9.1%), α-terpineol (4.9%) and limonene (4.6%) ²⁵⁾ which might be responsible for the anticonvulsant activity. The analgesic activity of linalool has been previously examined in two different pain models, including the acetic acid-induced writhing response and the hot plate test in mice, and since the results have shown marked analgesic activity ²⁶⁾. Furthermore, other constituents in neroli, such as linalyl acetate, nerolidol, farnesol, α-terpineol, or limonene, might be the related active ones also. Limonene has been reported as a potent antinociceptive compound in some biological assays ²⁷⁾. α-Terpineol also represented an important tool for the management and/or treatment of painful conditions in several pharmacological assays and was characterized as responsible compounds for the analgesic activity of the oils ²⁸⁾. α-Terpineol also represented an important tool for the management and/or treatment of painful conditions in several pharmacological assays and was characterized as responsible compounds for the analgesic activity of the oils ²⁹⁾.

The essential oil of Citrus aurantium L. var. amara, also known as neroli oil, has been reported to have antianxiety effects by regulating 5-HT (serotonin) receptors in rats ³⁰⁾ and to have antidepressant effects through the monoaminergic system in mice ³¹⁾. Neroli oil has also been reported to have sedative, antianxiety, and antidepressant effects on mice ³²⁾. In addition, limonene, one of the major chemical components in the essential oil of Neroli (Citrus aurantium L. var. amara), has been shown to have antianxiety ³³⁾ and motor relaxant effects, indicating sedative activity ³⁴⁾ in mice. Moreover, a study in rats reported that olfactory stimulation with grapefruit oil, which is rich in limonene, stimulated sympathetic nerves by activating histamine H1 receptors and that limonene treatment induced similar responses ³⁵⁾. Limonene-rich bergamot essential oil also demonstrated direct vasorelaxant effects ³⁶⁾.

Neroli essential oil also showed activity against acute and chronic inflammation. Carrageenan-induced edema has been commonly used as an experimental animal model for acute inflammation and is believed to be biphasic. The results for the paw edema showed significant reduction at doses of 40 and 80 mg/kg ³⁷⁾. The inhibitory activity shown by neroli during a period of 4 hour in carrageenan-induced paw inflammation was somehow similar to that exhibited by the group treated with diclofenac sodium (a nonsteroidal anti-inflammatory drug). These results indicate that neroli acts in later phases, probably involving arachidonic acid metabolites, which produce an edema dependent on neutrophils mobilization ³⁸⁾. The granulomatous tissue induction is a widely used method for the assessment of chronic anti-inflammatory substances ³⁹⁾. Neroli essential oil effectively and significantly reduced cotton pellet-induced granuloma, thereby suggesting its activity in the proliferative phase of the inflammation. The anti-inflammatory activity of neroli could be related to the inhibition of nitric oxide (NO) formation/release. Many reports have suggested that nitric oxide (NO), peripherally produced by different nitric oxide synthase (NOS) isoforms, contributes to edema formation ⁴⁰⁾. Regardless of the detailed mechanism, it is true that neroli produces an anti-inflammatory effect through the inhibition of NO production. Pharmacological evaluation of linalool in mice also revealed that linalool and the corresponding acetate play a major role in the anti-inflammatory activity displayed by the essential oils containing them, and provide further evidence suggesting that linalool and linalyl acetate-producing species are potentially anti-inflammatory agents ⁴¹⁾.

Neroli (Citrus aurantium L.) is used as an alternative treatment in some countries, including Iran, to relieve insomnia, anxiety, inflammation, depression, epilepsy, and seizures ⁴²⁾. Neroli essential oil has shown significant anticonvulsant activity and increases the latency period of tonic seizures in the pentylenetetrazol and maximal electroshock models ⁴³⁾. It was found that the Neroli blossoms extract also has a significant reduction effect on the latency of the onset of seizure and the duration of seizure with higher dose (300 mg/kg) ⁴⁴⁾ related to neroli (20 mg/kg) ⁴⁵⁾. Neroli (Citrus aurantium L.) blossom extract has also shown effectiveness in terms of reduction in preoperative anxiety before minor operations ⁴⁶⁾.

Neroli essential oil side effects

Neroli (bitter orange) is also employed in herbal medicine as a stimulant and appetite suppressant, due to its active ingredient, synephrine ⁴⁷⁾. Neroli (bitter orange) supplements have been linked to a number of serious side effects like fainting, heart-rhythm disorders, heart attack, stroke and even death ⁴⁸⁾. According to the National Center for Complementary and Integrative Health, there are case reports of healthy people experiencing fainting, heart attack, and stroke after taking bitter orange alone or with caffeine ⁴⁹⁾. Case reports have linked bitter orange supplements to strokes ⁵⁰⁾, ⁵¹⁾, angina ⁵²⁾ and ischemic colitis ⁵³⁾. Following an incident in which a healthy young man suffered a myocardial infarction (heart attack) linked to bitter orange, a case study found that dietary supplement manufacturers had replaced ephedra with its analogs from bitter orange ⁵⁴⁾. However, evidence regarding the effects of bitter orange (alone or combined with other substances, such as caffeine and green tea) on the heart and cardiovascular system are inconclusive ⁵⁵⁾. Because products that contain bitter orange may be unsafe, pregnant women and nursing mothers should avoid them.

In volunteers receiving skin applications of bitter orange peel oil expressed (5 μL/cm2 of 100% oil) under occlusion followed by exposure to visible light or ultraviolet A, all subjects exhibited phototoxic reactions.

Chronic exposure, cytotoxicity, carcinogenicity, or tumor initiation/promotion studies were not available ⁵⁶⁾.

What is patchouli

Patchouli (Pogostemon cablin) is commonly known as “guanghuoxiang” in Chinese, is a bushy herb that is a member of the mint family (Lamiaceae), with erect stems, reaching around 75 centimetres (2.5 ft) in height and bearing small, pale pink-white flowers ¹⁾. A strong-smelling oil taken from the patchouli leaves is used in perfumes, incense, detergents, insect repellents and hair conditioners. It has been used in some cultures as alternative medicines to prevent disease.

Patchouli (Pogostemon cablin) is traditionally used in China to treat various illnesses, including fever, common cold, diarrhea and nausea ²⁾. Previous studies have demonstrated that Patchouli also exerts numerous bioactivities, including radical-scavenging, anti-microbial, analgesic and anti-inflammatory activities ³⁾. Several studies have been carried out on the composition of Patchouli (Pogostemon cablin) and the presence of patchouli alcohol, pogostone, eugenol, α-bulnesene, rosmarinic acid, etc. has been revealed ⁴⁾. Patchouli essential oils constitute about 1.5% of Patchouli and among them >50% is patchouli alcohol ⁵⁾. Patchouli alcohol (see Figure 2), which is a tricyclic sesquiterpene, is the main active ingredient of Patchouli ⁶⁾. Oral administration of Patchouli alcohol has been demonstrated to offer protection against influenza virus infection in mice via the enhancement of host immune responses, and the attenuation of systemic and pulmonary inflammatory responses ⁷⁾. In addition, it has been reported that pretreatment with Patchouli alcohol attenuates reactive oxygen species (ROS) generation following Aβ25–35-induced toxicity ⁸⁾. These findings indicated that Patchouli alcohol possesses anti-inflammatory and antioxidative activities ⁹⁾. Patchouli alcohol has an oral median lethal dose value of 4,693 mg/kg in mice ¹⁰⁾.

Figure 1. Patchouli

Patchouli alcohol

Patchouli alcohol (C15H26O), a naturally occurring tricyclic sesquiterpene, is the critically biological active constituent among the patchouli oil extracted from Patchouli and usually used as a pivotal chemical marker compound for the assessments in quality control of Pogostemonis Herba and patchouli oil in China ¹¹⁾. However, the practices of using Patchouli alcohol are blank in medical field, despite Patchouli alcohol has been demonstrated in test tube studies to possess multibeneficial pharmacological properties, such as immunomodulatory, anti-inflammatory, antioxidative, antitumor, antimicrobial, insecticidal, antiatherogenic, antiemetic, whitening, and sedative activities ¹²⁾.

In nature, Patchouli alcohol primarily exists in volatile oil of Patchouli and its contents are about 48.8% ¹³⁾. In general, Patchouli alcohol contents were higher in the leaves than that in the root and/or stem and altered in different collection parts as well as harvest times. Patchouli alcohol is also detected within volatile oil from other plants, such as Herba Lysimachia paridiformis (22.54%) ¹⁴⁾, Rhizoma Valeriana jatamansi jones (5.88%) ¹⁵⁾, Rhizoma Nardostachys chinensis (4.5%) ¹⁶⁾, Radix Mallotus apelta (4.48%) ¹⁷⁾, Foliage Ficus microcarpa (4.05%) ¹⁸⁾, Herba Pholidota cantonensis (3.60%) ¹⁹⁾, Herba Asarum sieboldii (2.75%) ²⁰⁾, Herba Gendarussa vulgaris (2.68%) ²¹⁾, Radix Helleborus thibetanus (0.811%) ²²⁾, Herba Sedum sarmentosum (0.53%) ²³⁾, Aquilaria agallocha (0.392%) ²⁴⁾, Pericardium Citri reticulatae (China: Xinhui, 0.178%; Guangxi, 0.162%; and Fujian, 0.086%) ²⁵⁾, Fructus Periploca forrestii Schltr. (MAE, 0.12%; and SDE, 6012%) ²⁶⁾, and Foliage Microtoena patchouli ²⁷⁾.

Figure 2. Patchouli alcohol chemical structure

Figure 3. Possible mechanisms of bioactivities of Patchouli alcohol in immunomodulation, antitumor, anti-inflammation, and antioxidation

Note: Arrow up denotes activation or increase; arrow down denotes suppression or decrease. Inflammation and oxidation interact with each other.

The present information exhibited remarkably therapeutic properties of Patchouli Alcohol in vivo (animal) and in vitro (test tube) studies, which could contribute to the prevention and treatment of many diseases, such as immune disorders, infections by microbes, mosquitoes or Trypanosoma cruzi, ALI, mastitis, gastric ulcer, skin photoaging, atherosclerosis, and tumor. However, further studies are required to investigate the safety and toxicity Patchouli alcohol in both animals and humans. And so far there has been no well designed human clinical trials to support the purported benefits of Patchouli, Patchouli alcohol or Patchouli essential oil. Finally, any medicinal benefit of Patchouli remains unclear.

Patchouli essential oil

The dry leaves of patchouli on steam distillation, requiring rupture of its cell walls by steam scalding, light fermentation, or drying to yield an essential oil called the patchouli oil. Patchouli essential oil is hence an important ingredient in many fine fragrance products such as perfumes, as well as in soaps and cosmetic products ³⁰⁾. Results of High Performance Thin Layer Chromatography studies indicated that the ethyl acetate extract of Patchouli leaves included triterpenes, as 10 and 14 peaks of ultra violet (UV) absorption were observed in 254 nm and 366 nm, respectively. Hence, triterpenes may be responsible for antidermatophytic activity of this plant ³¹⁾.

Moreover, patchouli oil in the plant is widely used in Traditional Chinese Medicine as it offers various types of pharmacological activities ³²⁾. It has also been reported to strengthen the immune activity and resistance to bacterial action ³³⁾. The composition of the patchouli oil is complex like many essential oils, which consist of the major components such as patchoulol alcohol and pogostone etc. The mechanism of action of major pharmacologic components in patchouli oil as an antibacterial agent has not been reported. However, in an in-vitro (test tube) study, the main compounds in patchouli essential oil seems to be patchouli alcohol and pogostone, whose composition exceeded 60% (g/g) in patchouli oil samples – all have good antibacterial activities ³⁴⁾.

Figure 4. 26 chemical compounds in Patchouli oil

Patchouli oil uses

Perfume

Patchouli oil is an important essential oil in the perfume industry, keeping a base and lasting character to a fragrance. For characteristic pleasant and long lasting woody and camphoraceous odor, patchouli oil is appreciated and very suitable for the utilization of decorative cosmetics, fragrances, shampoo, toilet soaps, paper towels, air fresheners and other toiletries as well as noncosmetic products such as household cleaners and detergents ³⁶⁾.

Insect repellent

One study suggests that patchouli oil may serve as an all-purpose insect repellent ³⁷⁾. More specifically, the patchouli plant is claimed to be a potent repellent against the Formosan subterranean termite ³⁸⁾. The experiment on repellent and toxic effects of Patchouli alcohol on Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae) was carried out by Zhu et al. ³⁹⁾. The results uncovered that patchouli alcohol pretreatment resulted in elevation in mortality percentage and decline in termites feeding, contacting and tunneling behaviors, and particularly the internal tissue of termites was destructed inside the exoskeleton when patchouli alcohol was topically applied into the dorsum. Furthermore, patchouli alcohol was witnessed to have obvious repellency and toxicity towards mosquitoes. Patchouli alcohol, at 2 mg/cm2 concentration, was the most effective for repellent activity, providing 100% protection up to 280 min, against Ae aegypti, An. Stephensi, and Cx. quinquefasciatus, and for pupicidal activity at 100 mg/L concentration, providing 28.44, 26.28, and 25.36 against above vector mosquitoes tested ⁴⁰⁾. These findings provide experimental basis for the development of patchouli alcohol as an ideal eco-friendly pesticide for the control of termites and mosquitoes.

Incense

Patchouli is an important ingredient in East Asian incense. Both patchouli oil and incense underwent a surge in popularity in the 1960s and 1970s in the US and Europe, mainly as a result of the hippie movement of those decades ⁴¹⁾.

Culinary

Patchouli leaves have been used to make an herbal tea. In some cultures, patchouli leaves are eaten as a vegetable or used as a seasoning.

What is peppermint tea good for

Peppermint (Mentha piperita L.) is one of the most widely consumed single ingredient herbal teas or tisanes ¹⁾. Peppermint tea, brewed from the plant leaves, and the essential oil of peppermint are used in traditional medicines. Peppermint is a hybrid mint, a cross between two types of mint water mint [Mentha aquatica] and spearmint [Mentha spicata L.] also known as Mentha piperita. Indigenous to Europe and the Middle East, the plant is now widespread in cultivation in many regions of the world ²⁾. Gas chromatography–mass spectrometry analysis of Peppermint revealed the existence of menthone (25.4%), 1,8-cineole (17.7%) and menthol (12.1%) as the main components, while the essential oil contained high amounts of menthol (46.8%) and menthone (25.6%) ³⁾.

Peppermint leaves are aromatic perennial herb cultivated in most part of the world and it is used as folk medicine and frequently used in herbal tea and for culinary purpose to add flavor and aroma ⁴⁾. Best known for its flavoring and fragrance properties, peppermint leaves (fresh and dried) and the essential oil extracted from the leaves are used in many food, cosmetic and pharmaceutical products. Peppermint is used for flavoring ice cream, candy, fruit preserves, alcoholic beverages, chewing gum, toothpaste, and some shampoos, soaps and skin care products ⁵⁾. The phenolic constituents of Peppermint leaves include rosmarinic acid and several flavonoids, primarily eriocitrin, luteolin and hesperidin ⁶⁾. The peppermint essential oil is rich in menthol, l-menthone, pulegone, piperitone, menthol acetate, piperitenone menthone, carvone, menthofuran, isomenthone, menthyl acetate, isopulegol, menthol, 3-octanol, pulegone; hence, it also used as natural antioxidants ⁷⁾, ⁸⁾. The list of purported benefits and uses of peppermint as a folk remedy or in complementary and alternative medical therapy include: biliary disorders, dyspepsia, enteritis, flatulence, gastritis, intestinal colic, and spasms of the bile duct, gallbladder and gastrointestinal (GI) tract.

Today, peppermint is used as a dietary supplement for irritable bowel syndrome (IBS), other digestive problems, the common cold, headaches, and other conditions. Peppermint oil is also used topically (applied to the skin) for headache, muscle aches, itching, and other problems. Peppermint leaf is available in teas, capsules, and as a liquid extract. Peppermint oil is available as liquid solutions and in capsules, including enteric-coated capsules.

Figure 1. Peppermint

How to make peppermint tea

Wash and tear up the fresh peppermint leaves. Put them in a French press or teapot and pour some boiling water over them.

Directions:

• Boil about 3 or 4 cups of water.
• Add the peppermint leaves and shut the heat off.
• Let the tea steep for about 5 minutes, depending on how strong you want your tea.
• Pour through a tea strainer.
• Add the honey and pour into cups.
• The tea can be made from fresh leaves or dried leaves.

Does peppermint tea have caffeine ?

No, peppermint leaves have no caffeine. See Table 1 below.

The chemical components of peppermint leaves and oil vary with plant maturity, variety, geographical region and processing conditions ⁹⁾.

Table 1. Peppermint (fresh) nutrition facts

Health benefits of peppermint tea

In Germany, peppermint leaf is licensed for use as a standard medicinal tea to treat dyspepsia. The German Commission E has also approved the internal use of the leaf for spastic complaints of the GI tract, gallbladder and bile ducts ¹¹⁾. Peppermint oil is approved for internal use in the event of spastic discomfort of the upper GI tract and bile ducts, irritable colon or irritable bowel syndrome (IBS), catarrahs of the respiratory tract and inflammation of the oral mucosa. Externally, the use of peppermint oil is approved for myalgia and neuralgia. With the exception of peppermint oil and IBS, studies providing evidence to either support or refute the applicability of peppermint as a treatment for many of these conditions in humans is somewhat limited (see Table 2).

Table 2. Human studies examining the effects of orally ingested peppermint leaves (Mentha piperita)

Peppermint tea and peppermint oil toxicity and side effects

Toxicology studies of peppermint oil and its components have been performed in animals. Histopathological changes in the white matter of the cerebellum were seen in rats (n = 20) given peppermint oil at doses of 40 and 100 mg/kg orally for 28 days, but no adverse effects were observed at 10 mg/kg ¹⁵⁾. No adverse effects were observed at 10 mg/kg. In a comparable 90 day rat study (n = 28), cyst-like spaces in the white matter of the cerebellum and hyaline droplets in the proximal tubules of the kidneys were observed in the highest dose group only ¹⁶⁾. Interestingly, the extension of the cyst-like spaces was not aggravated with prolonged dosing in this study. Menthol administered to rats by gavage at 200, 400 and 800 mg/kg for 28 days significantly increased absolute and relative liver weights and the vacuolization of hepatocytes at all doses, although no sign of encephalopathy was observed ¹⁷⁾. At 80 and 160 mg/kg, pulegone administered for 28 days induced atonia, decreased blood creatinine levels, lowered body weight and caused histopathological changes in the liver and white matter of the cerebellum ¹⁸⁾. No adverse effects were observed with 20 mg/kg pulegone. Menthone given orally to rats (n = 20) at 200, 400 and 800 mg/kg for 28 days decreased creatinine and increased alkaline phosphatase in a dose-dependent manner, increased bilirubin and liver and spleen weights, and also caused histopathological changes in the white matter of the cerebellum in the two highest dose groups ¹⁹⁾. The accumulation of protein droplets containing α2μ-globulin in proximal tubular epithelial cells of rats (n = 10/group) was observed after the administration of either 500–1000 mg/kg 1,8-cineole or 800–1600 mg/kg limonene for 28 days, however, no histopathological changes were observed in the brain ²⁰⁾.

• A study on diet and the development of gastroesophageal reflux disease (GERD) ²¹⁾ found that frequent consumption of peppermint tea was a risk factor for the development of gastroesophageal reflux disease (GERD). Gastroesophageal reflux disease (GERD) is a chronic gastrointestinal disease that significantly reduces quality of life and, in some patients, leads to serious complications, such as oesophageal stricture, gastrointestinal bleeding, or Barrett’s oesophagus. According to various sources, the typical symptoms of this disease (heartburn, discomfort in the upper abdomen, acid eructation) are experienced daily by 4–10%, and weekly by 10–30% of the adult population in Western countries ²²⁾. Literature sources suggest that peppermint decreases lower esophageal sphincter (LES) tension; moreover, peppermint oil (studied in animal models) relaxes the smooth muscles of the alimentary tract ²³⁾. Oliveria et al. ²⁴⁾ found that 8% of heartburn patients reported complaints after consuming peppermint. In contrast, Terry et al. ²⁵⁾ and Bulat et al. ²⁶⁾ did not observe any effect of consuming products and beverages with peppermint on reflux episodes. This issue requires further research. Nevertheless, it is advisable to inform the patients that peppermint infusion is not always a recommended method of soothing stomach complaints.
• The long-term safety of consuming large amounts of peppermint leaf is currently unknown.

• Although peppermint is commonly available as an herbal supplement, there are no established, consistent manufacturing standards for it, and some peppermint products may be contaminated with toxic metals or other substituted compounds.
• Peppermint oil appears to be safe when taken orally (by mouth) in the doses commonly used. Excessive doses of peppermint oil can be toxic.
• Short-term and sub-chronic peppermint oil oral studies reported cystlike lesions in the cerebellum in rats that were given doses of Peppermint Oil containing pulegone, pulegone alone, or large amounts (>200 mg/kg/day) of menthone. Pulegone is also a recognized hepatotoxin ²⁷⁾.
• Possible side effects of peppermint oil include allergic reactions and heartburn. Capsules containing peppermint oil are often enteric-coated to reduce the likelihood of heartburn. If enteric-coated peppermint oil capsules are taken at the same time as antacids, the coating can break down too quickly.
• Like other essential oils, peppermint oil is highly concentrated. When the undiluted essential oil is used for health purposes, only a few drops are used.
• Side effects of applying peppermint oil to the skin can include skin rashes and irritation. Repeated intradermal dosing with Peppermint Oil produced moderate and severe reactions in rabbits, although Peppermint Oil did not appear to be phototoxic. Peppermint oil should not be applied to the face or chest of infants or young children because serious side effects may occur if they inhale the menthol in the oil.

A review on the use of peppermint oil, leaf extract, leaf and leaf water in cosmetic formulations by Nair ²⁸⁾ concluded that each are considered safe, although the concentration of pulegone in products containing these ingredients should be limited to 1%. Although the toxicity of menthol is considered to be low, it has the ability to enhance the penetration and absorption of other agents contained in some formulations, thereby increasing the effective dose of these agents at the indicated intake. A few case study reports have described contact sensitivities to peppermint oil and its components in topical and oral preparations ²⁹⁾, ³⁰⁾, but a patch test study of 4000 patients by Kanerva et al. ³¹⁾ found that menthol and peppermint oil provoked neither allergic nor irritant reactions.

Akdogan et al. ³²⁾ reported increased follicle stimulating hormone (FSH) and luteinizing hormone  (LH) levels and decreased testosterone levels in rats given 20 g/L peppermint tea in place of their drinking water. As opposed to spearmint tea, the only effect of peppermint on testicular tissue was segmental maturation arrest in the semniferous tubules. There are no chronic toxicity studies of peppermint in humans, although the German Commission E ³³⁾ reports that the use of peppermint oil is contraindicated in patients with bile duct, gallbladder and liver disorders. Caution is also recommended for the use of peppermint oil capsules in patients with GI reflux, hiatal hernia or kidney stones.

What is peppermint oil good for

Peppermint is a hybrid mint, a cross between two types of mint water mint [Mentha aquatica] and spearmint [Mentha spicata L.] also known as Mentha piperita. Indigenous to Europe and the Middle East, the plant is now widespread in cultivation in many regions of the world ¹⁾. Peppermint has been used for health purposes for several thousand years. It is mentioned in records from ancient Greece, Rome, and Egypt. Both peppermint leaves and the essential oil from peppermint have been used for health purposes. However, peppermint was not recognized as a distinct kind of mint until the 1700s. Essential oils are very concentrated oils containing substances that give a plant its characteristic odor or flavor. Peppermint is a common flavoring agent in foods, and peppermint oil is used to create a pleasant fragrance in soaps and cosmetics.

Peppermint leaves are aromatic perennial herb cultivated in most part of the world and it is used as folk medicine and frequently used in herbal tea and for culinary purpose to add flavor and aroma ²⁾. The peppermint essential oil is rich in menthol, l-menthone, pulegone, piperitone, menthol acetate, piperitenone menthone, carvone, menthofuran, isomenthone, menthyl acetate, isopulegol, menthol, 3-octanol, pulegone; hence, it also used as natural antioxidants ³⁾, ⁴⁾. Menthol activates cold-sensitive TRPM8 receptors in the skin and mucosal tissues, and is the primary source of the cooling sensation that follows the topical application of peppermint oil ⁵⁾. In addition, δ-cadinene, copaene, eugenol, methyl pivalate, menthomenthene, thujopsene, caryophyllene oxide also some of the compound identified in peppermint essential oil and demonstrated antifungal activity and antibacterial activity ⁶⁾, ⁷⁾. Peppermint essential oil have shown potent inhibitory activity against several microorganisms such as Penicillium digitatum, Aspergillus flavus, Aspergillus niger, Candida albicans, Saccharomyces cerevisiae Mucor spp., and Fusarium oxysporum ⁸⁾. Peppermint oil has been reported as antifungal agent for several mycotoxigenic speceies by Silva et al., 2012 ⁹⁾; Aspergillus flavus and Aspergillus parasiticus, Freire et al. ¹⁰⁾, in 2012 reported against Aspergillus ochraceous, Colletotrichum gloeosporioides, Colletotrichum musae, F. oxysporum, Fusarium semitectum. Peppermint essential oil anti-inflammatory ¹¹⁾, antioxidant ¹²⁾ and cytotoxic effects were reported by Sun et al. 2014 ¹³⁾. Currently, peppermint essential oil has been widely used in cosmetic, food and pharmaceutical industries.

Peppermint oil has a high concentration of natural pesticides, mainly pulegone and menthone ¹⁴⁾. It is known to repel some pest insects, including mosquitos, and has uses in organic gardening ¹⁵⁾.

Today, peppermint is used as a dietary supplement for irritable bowel syndrome (IBS), other digestive problems, the common cold, headaches, and other conditions. Peppermint oil is also used topically (applied to the skin) for headache, muscle aches, itching, and other problems. Peppermint leaf is available in teas, capsules, and as a liquid extract. Peppermint oil is available as liquid solutions and in capsules, including enteric-coated capsules.

Figure 1. Peppermint

Chemical Composition and Anti-Inflammatory, Cytotoxic and Antioxidant Activities of Peppermint Essential Oil from Leaves

51 volatile constituents in peppermint essential oil have been evaluated for their anti-inflammatory, cytotoxic and antioxidant activities ¹⁶⁾. Test tube and animal studies showed that peppermint essential oil had a potent anti-inflammatory activity in the croton oil-induced mouse ear edema model, and the possible action mechanism might be attributed to its inhibitory effect on the production of nitric oxide (NO) and prostaglandin E2 (PGE2). Peppermint essential oil was also found to be active against SPC-A-1, K562 and SGC-7901 cancer cell lines. In addition, peppermint essential oil had a moderate antioxidant activity.

Peppermint antioxidant actions were previously suggested to be due to the presence of phenolic constituents in its leaves including rosmarinic acid and different flavonoids such as rutin, naringin, eriocitrin, luteolin, and hesperidin ¹⁷⁾, ¹⁸⁾. High-performance liquid chromatography (HPLC) analysis of the peppermint leaf hydroalcoholic extract detected some peaks that coeluted with pure ursolic acid, epicatechin, caffeic acid, rutin, quercetin, naringenin, and kaempferol. These compounds were previously shown to act as anti-inflammatory and/or antioxidants ¹⁹⁾. In animal studies, it was clearly demonstrated in the Ames test that peppermint has antimutagenic effects once it significantly inhibited the shamma—a tobacco product—induced oral carcinogenesis in the hamster cheek pouch ²⁰⁾. These results may serve as valuable research references for clinical research of medicines for treatment of inflammation and cancer in the future.

Table 1. Chemical composition of peppermint essential oil

Note:

Peppermint essential oil benefits

In Eastern and Western traditional medicines, peppermint and its oil have been used in antispasmodics, aromatics, antiseptics or even medications for the treatment of colds, cramps, indigestions, nausea, sore throat, toothache or even cancer ²²⁾. Modern pharmacology research has demonstrated that peppermint possesses antioxidant, antitumor, antiallergenic, antiviral and antibacterial activities ²³⁾, ²⁴⁾, ²⁵⁾, ²⁶⁾.

Peppermint oil for IBS (Irritable Bowel Syndrome)

Irritable bowel syndrome (IBS) is a common condition with a community prevalence of 10-15% of the general population ²⁷⁾. The annual incidence in primary care is around 0.8%, and the prevalence of patients diagnosed in primary care is about 3-4% ²⁸⁾. The disorder is difficult to treat, hence the wide range of treatments used—dietary exclusion, fiber supplements, and probiotics; antispasmodic drugs, antidiarrhoeal agents, and laxatives; antidepressants, hypnotherapy, and cognitive behavioral therapy.

In this systematic review and meta-analysis ²⁹⁾, the researchers investigated the effectiveness of antispasmodics, fiber and peppermint oil in the treatment of IBS (irritable bowel syndrome). Individual trials on these treatments have been of variable quality with conflicting results, and previous systematic reviews have also resulted in different conclusions. This is a high quality systematic review that looked into all published research of peppermint oil, muscle relaxants (or antispasmodics) and fiber used in the treatment of IBS (irritable bowel syndrome). The three treatments were all found to reduce the risk of having persistent symptoms (such as abdominal pain and bloating) compared to placebo.

The researchers searched medical research databases to identify all randomized controlled trials (including foreign language studies) involving adults who met diagnostic criteria for IBS and who had received investigations, if necessary, to exclude an underlying cause. Studies had to compare antispasmodics, fibre or peppermint oil with an inactive placebo drug. They also had to include a follow-up of at least one week with an assessment of cure or improvement of symptoms. The researchers also hand-searched abstracts of conference proceedings for potential studies and looked at reference lists of all selected studies.

The main outcome that the researchers looked for was the efficacy of any of the three treatments compared to placebo on all IBS symptoms or just abdominal pain. The researchers assessed the quality of the trials and results were pooled to give the relative risk of symptoms persisting after treatment.

The search found 35 eligible studies for inclusion: 19 involving antispasmodics, nine of fibre, four of peppermint oil, and three involving antispasmodics or fibre.

The 12 trials of fiber had a total of 591 people with IBS. Treatments included bran (five studies), ispaghula husk (six studies) and, in one study, concentrated fiber. Overall, any fiber treatment reduced the risk of persistent symptoms by 13%, but this result was only of borderline significance. The only individual treatment that gave a significant reduction in symptoms was ispaghula.

The 22 trials of antispasmodics included 1,778 people with IBS and used a variety of drugs (12 in total) at different doses. Overall, antispasmodics significantly reduced the risk of persistent symptoms by 32% ³⁰⁾. Of the individual drugs, only hyoscine, cimetropium, pinaverium and otilonium gave consistent significant evidence of benefit.

The four trials of peppermint oil, at different doses, included 392 people with IBS. Across these studies, 26% of those randomized to peppermint oil experienced persistent symptoms compared to 65% of those assigned to placebo. This gave an overall 57% reduction in risk of persistent symptoms when taking peppermint oil ³¹⁾.

The number of people that would need to be treated to prevent one person from having persistent abdominal symptoms was 2.5 for peppermint, five for antispasmodics and 11 for fiber ³²⁾.

However, there are several points to bear in mind:

• The trials included in the review were of variable size, included slightly different patient groups, fulfilling different diagnostic criteria for IBS, different doses and treatment durations, were carried out in different settings (e.g. primary or secondary care), and used different criteria for symptom improvement. In the antispasmodic and peppermint oil trials, heterogeneity (diversity) was demonstrated to be statistically significant, i.e. different methods and results were obtained between trials, which may call into question the validity of combining results of the studies in this way.
• Although peppermint oil was highlighted in the review, as it demonstrated the greatest reduction in risk, it only included four trials with 392 people. This limits the strength of the conclusions that can be drawn from the combination of these studies. However, this is partly countered by the fact that three of the studies were of high quality and there was no statistical heterogeneity when they were combined. This increases the confidence in the finding.
• The authors report that none of the trials state whether the allocation of the treatments was concealed. This means that practitioners may have been aware of whether the active treatment or placebo was being given to participants. It has been found that this type of bias may give an overestimation of treatment effect.
• Adverse effects were not consistently reported across studies, so no firm conclusions can be made about the safety of any of the three treatments.
• The trials have only compared each treatment to inactive placebo, so it cannot be assumed that any one treatment is more effective than the others.

IBS has no single identified cause. It is not a pathological condition, i.e. there is no underlying disease process, but the bowel does not function properly, causing discomfort and inconvenience for sufferers. This review provides evidence to support the use of symptomatic treatments such as peppermint oil ³³⁾.

What have we learned ?

• Peppermint oil has been studied most extensively for IBS. Results from several studies indicate that peppermint oil in enteric-coated capsules may improve IBS symptoms.
• A few studies have indicated that peppermint oil, in combination with caraway oil, may help relieve indigestion, but this evidence is preliminary and the product that was tested is not available in the United States.
• Peppermint oil has been used topically for tension headaches and a limited amount of evidence suggests that it might be helpful for this purpose.
• There’s not enough evidence to allow any conclusions to be reached about whether peppermint oil is helpful for nausea, the common cold, or other conditions.
• There’s not enough evidence to show whether peppermint leaf is helpful for any condition.

Peppermint oil toxicity and safety

Toxicology studies of peppermint oil and its components have been performed in animals. Histopathological changes in the white matter of the cerebellum were seen in rats (n = 20) given peppermint oil at doses of 40 and 100 mg/kg orally for 28 days, but no adverse effects were observed at 10 mg/kg ³⁴⁾. No adverse effects were observed at 10 mg/kg. In a comparable 90 day rat study (n = 28), cyst-like spaces in the white matter of the cerebellum and hyaline droplets in the proximal tubules of the kidneys were observed in the highest dose group only ³⁵⁾. Interestingly, the extension of the cyst-like spaces was not aggravated with prolonged dosing in this study. Menthol administered to rats by gavage at 200, 400 and 800 mg/kg for 28 days significantly increased absolute and relative liver weights and the vacuolization of hepatocytes at all doses, although no sign of encephalopathy was observed ³⁶⁾. At 80 and 160 mg/kg, pulegone administered for 28 days induced atonia, decreased blood creatinine levels, lowered body weight and caused histopathological changes in the liver and white matter of the cerebellum ³⁷⁾. No adverse effects were observed with 20 mg/kg pulegone. Menthone given orally to rats (n = 20) at 200, 400 and 800 mg/kg for 28 days decreased creatinine and increased alkaline phosphatase in a dose-dependent manner, increased bilirubin and liver and spleen weights, and also caused histopathological changes in the white matter of the cerebellum in the two highest dose groups ³⁸⁾. The accumulation of protein droplets containing α2μ-globulin in proximal tubular epithelial cells of rats (n = 10/group) was observed after the administration of either 500–1000 mg/kg 1,8-cineole or 800–1600 mg/kg limonene for 28 days, however, no histopathological changes were observed in the brain ³⁹⁾.

• Although peppermint is commonly available as an herbal supplement, there are no established, consistent manufacturing standards for it, and some peppermint products may be contaminated with toxic metals or other substituted compounds.
• Peppermint oil appears to be safe when taken orally (by mouth) in the doses commonly used. Excessive doses of peppermint oil can be toxic.
• Short-term and sub-chronic peppermint oil oral studies reported cystlike lesions in the cerebellum in rats that were given doses of Peppermint Oil containing pulegone, pulegone alone, or large amounts (>200 mg/kg/day) of menthone. Pulegone is also a recognized hepatotoxin ⁴⁰⁾.
• Possible side effects of peppermint oil include allergic reactions and heartburn. Capsules containing peppermint oil are often enteric-coated to reduce the likelihood of heartburn. If enteric-coated peppermint oil capsules are taken at the same time as antacids, the coating can break down too quickly.
• Like other essential oils, peppermint oil is highly concentrated. When the undiluted essential oil is used for health purposes, only a few drops are used.
• Side effects of applying peppermint oil to the skin can include skin rashes and irritation. Repeated intradermal dosing with Peppermint Oil produced moderate and severe reactions in rabbits, although Peppermint Oil did not appear to be phototoxic. Peppermint oil should not be applied to the face or chest of infants or young children because serious side effects may occur if they inhale the menthol in the oil.
• A study on diet and the development of gastroesophageal reflux disease (GERD) ⁴¹⁾ found that frequent consumption of peppermint tea was a risk factor for the development of gastroesophageal reflux disease (GERD). Gastroesophageal reflux disease (GERD) is a chronic gastrointestinal disease that significantly reduces quality of life and, in some patients, leads to serious complications, such as oesophageal stricture, gastrointestinal bleeding, or Barrett’s oesophagus. According to various sources, the typical symptoms of this disease (heartburn, discomfort in the upper abdomen, acid eructation) are experienced daily by 4–10%, and weekly by 10–30% of the adult population in Western countries ⁴²⁾. Literature sources suggest that peppermint decreases lower esophageal sphincter (LES) tension; moreover, peppermint oil (studied in animal models) relaxes the smooth muscles of the alimentary tract ⁴³⁾. Oliveria et al. ⁴⁴⁾ found that 8% of heartburn patients reported complaints after consuming peppermint. In contrast, Terry et al. ⁴⁵⁾ and Bulat et al. ⁴⁶⁾ did not observe any effect of consuming products and beverages with peppermint on reflux episodes. This issue requires further research.
• The long-term safety of consuming large amounts of peppermint leaf is currently unknown.

A review on the use of peppermint oil, leaf extract, leaf and leaf water in cosmetic formulations by Nair ⁴⁷⁾ concluded that each are considered safe, although the concentration of pulegone in products containing these ingredients should be limited to 1%. Although the toxicity of menthol is considered to be low, it has the ability to enhance the penetration and absorption of other agents contained in some formulations, thereby increasing the effective dose of these agents at the indicated intake. A few case study reports have described contact sensitivities to peppermint oil and its components in topical and oral preparations ⁴⁸⁾, ⁴⁹⁾, but a patch test study of 4000 patients by Kanerva et al. ⁵⁰⁾ found that menthol and peppermint oil provoked neither allergic nor irritant reactions.

Akdogan et al. ⁵¹⁾ reported increased follicle stimulating hormone (FSH) and luteinizing hormone  (LH) levels and decreased testosterone levels in rats given 20 g/L peppermint tea in place of their drinking water. As opposed to spearmint tea, the only effect of peppermint on testicular tissue was segmental maturation arrest in the semniferous tubules. There are no chronic toxicity studies of peppermint in humans, although the German Commission E ⁵²⁾ reports that the use of peppermint oil is contraindicated in patients with bile duct, gallbladder and liver disorders. Caution is also recommended for the use of peppermint oil capsules in patients with GI reflux, hiatal hernia or kidney stones.

What is reishi mushroom

Reishi (Ganoderma lucidum) also known as Reishi in Japan, Lingzhi in China, Ling chih and Ling chi mushroom in other countries, is a type of mushroom of the Polyporaceae family that grows on the stumps of oak and plum trees over a period of approximately 9 months in Asia ¹⁾. Reishi mushroom is not edible ²⁾. Reishi is popular among consumers in Japan, China and Korea where it is widely used by Asian physicians and herbalists. This medicinal mushroom has been used in Asia for thousands of years to increase energy, stimulate the immune system, and promote health and longevity ³⁾. In the US, Reishi is included in the American Herbal Pharmacopoeia and is most often recommended for its immune-supporting effects ⁴⁾. In Poland and other countries outside Asia, Reishi mushroom is used as a daily food supplement that adapts itself to correct imbalances in the body ⁵⁾. Influenced by an increasing number of studies into Reishi mushroom, modern uses of Reishi mushroom include treatment for coronary heart disease, arteriosclerosis, hepatitis, arthritis, nephritis, bronchitis, hypertension, cancer and gastric ulcers ⁶⁾.

Several classes of bioactive substances, such as triterpenoids, polysaccharides, nucleosides, sterols, and alkaloids, have been isolated from Reishi mushroom ⁷⁾. Both in vitro (test tube) and in vivo (animal) studies with Reishi mushroom have demonstrated that Reishi mushroom polysaccharides have anti-tumor activity through their immunomodulatory, anti-angiogenic, and cytotoxic effects. However, there are many questions that need to be answered before it is accepted and used as an anti-tumor agent ⁸⁾, ⁹⁾, ¹⁰⁾.

Figure 1. Reishi mushroom

Reishi mushroom extract

A systematic laboratory research elucidates that the anticancer and immunomodulatory properties of Reishi mushroom are largely contained in its diverse chemical constituents, whereas polysaccharides and triterpenes are two groups of prominent bioactive components ¹¹⁾.

The polysaccharides from Reishi mushroom are believed to trigger an indirect antitumour mechanism in which the host immune system is altered to target the tumor cells. The active polysaccharides are largely in the form of beta-glucans. It has been shown that beta-glucans have the ability to induce both innate and adaptive immune responses. The targeted immune cells include macrophages, neutrophils, monocytes, natural killer (NK) cells and dendritic cells. The branched chains of beta-glucans act on complement receptor type 3 (CR-3) triggering a series of molecular pathways such as NF-κB, mitogen-activated protein kinase (MAPK) and protein kinase C (PKC), which in turn, activate the host immune response for immune cell proliferations ¹²⁾. Beta-glucans also act on dectin-1 receptor and toll-like receptor 2 (TLR-2) ¹³⁾. The resultant actions are enhanced maturation of dendritic cells as well as increased opsonic and non-opsonic phagocytosis. Subsequently, cytokine production and splenic NK-cell cytotoxicity are increased ¹⁴⁾. All of these immune reinforcements are believed to have a contribution to the antitumour properties of Reishi mushroom ¹⁵⁾. In addition, Reishi mushroom is the only known source of a particular group of triterpenes, also known as ganoderic acids, which have been found to have direct cancer cell cytotoxicity on a wide variety of cancer cell lines, such as murine Lewis lung carcinoma (LLC) and Meth-A, and many of them have been suggested to counter angiogenesis and metastasis ¹⁶⁾.

Reishi mushroom health benefits

Prompted by the promising anticancer potential established by laboratory studies, a few randomized controlled trials have been conducted to evaluate the clinical effectiveness of Reishi mushroom. However, the majority of clinical trials are conducted in Asia and published in Asian databases. Full-text publications are usually not available in English.

In 2016 a well conducted Cochrane Review ¹⁷⁾ identified and subsequently included five relevant randomized controlled trials. A total of 373 subjects were analyzed. A meta-analysis was performed to pool available data from individual trials. The review results found that patients with Reishi mushroom extract in their anticancer regimen were 1.27 times more likely to respond to chemotherapy or radiotherapy than those without ¹⁸⁾. However, the data failed to demonstrate significant effect on tumor shrinkage when it was used alone. In addition, reishi mushroom could stimulate host immune functions by considerably increasing CD3, CD4 and CD8 lymphocyte percentages. Nevertheless, natural killer (NK)-cell activity, which has been suggested to be an indicator of self-defence against tumor cell, was marginally elevated. Patients in the Reishi mushroom group were found to have a relatively better quality of life after treatment than those in the control group ¹⁹⁾. A few cases of minor side effect associated with Reishi mushroom treatment including nausea and insomnia were reported. The review authors concluded that the review did not find sufficient evidence to justify the use of Reishi mushroom as a first-line treatment for cancer ²⁰⁾. It remains uncertain whether Reishi mushroom helps prolong long-term cancer survival. However, Reishi mushroom could be administered as an alternative adjunct to conventional treatment in consideration of its potential of enhancing tumor response and stimulating host immunity. Reishi mushroom was generally well tolerated by most participants with only a scattered number of minor adverse events. No major toxicity was observed across the studies. Although there were few reports of harmful effect of Reishi mushroom, the use of its extract should be judicious, especially after thorough consideration of cost-benefit and patient preference. Future studies should put emphasis on the improvement in methodological quality and further clinical research on the effect of Reishi mushroom on cancer long-term survival are needed. No significant haematological or hepatological toxicity was reported.

In a study on the effect of Reishi mushroom in preventing obesity and weight gain in mice fed high-fat diet for eight weeks ²¹⁾. This study of Reishi mushroom in mice eating a high-fat diet found that it may help to reduce weight and fat gain, reduce inflammation and improve the levels of “good” gut bacteria in the gut ²²⁾. It also appeared to reduce the risk of insulin resistance. Reishi mushroom was not seen to have a significant effect for mice fed a normal diet. The results of this study suggest a possible use for the Reishi mushroom extract, but randomized controlled trials in humans are required to determine safety and effectiveness for preventing weight gain. The same is true for any other conditions that Reishi mushroom is currently believed to improve. Either way, it is clear that eating a high-fat diet was the cause of the increased weight gain and body fat in these mice. Even if the Reishi mushroom extract is found to help prevent weight gain in humans, it is likely to be healthier to avoid a diet very high in fat. Eating a balanced diet including plenty of fruit and vegetables and taking regular exercise based on your ability is the best way to combat obesity. Reishi mushroom supplements are available to buy online but we wouldn’t recommend doing so. Just because something is “natural” doesn’t mean it is safe. The supplements can cause thinning of the blood, which could be very dangerous for people with high blood pressure. They are also known to interact in adverse ways with certain medications.

In another well conducted 2015 Cochrane Review ²³⁾ to evaluate the effectiveness of Reishi mushroom for the treatment of pharmacologically modifiable risk factors of cardiovascular disease in adults. There is no agreed dosage for Reishi mushroom treatment, however, most recommended amounts vary between 1.5 g and 9 g of dried Reishi mushroom extract per day ²⁴⁾. There are some claims that spores contain higher quantities of the active constituents. This has not been determined by research, and any medicinal benefit is unclear. Results from two studies showed that Reishi mushroom was not associated with statistically or clinically significant reduction in HbA1c (130 participants), total cholesterol (107 participants ), low-density lipoprotein cholesterol (107 participants), or body-mass index (107 participants). All other analyses were from a single study of 84 participants. The review authors found no improvement for fasting plasma glucose. Measures of post-prandial blood glucose level found inconsistent results, being in favor of placebo for ‘2-hour post-prandial blood glucose’ and in favor of Reishi mushroom for ‘plasma glucose under the curve at 4th hour’. There were no statistically significant differences between groups for blood pressure or triglycerides. Participants who took Reishi mushroom for four months were 1.67 times more likely to experience an adverse event than those who took placebo but these were not serious side effects. In conclusion, evidence from a small number of randomized controlled trials does not support the use of Reishi mushroom for treatment of cardiovascular risk factors in people with type 2 diabetes mellitus. Future research into the efficacy of Reishi mushroom should be placebo-controlled and adhere to clinical trial reporting standards ²⁵⁾.

What is royal jelly

Royal jelly is a honey bee secretion that is used in the nutrition of larvae, as well as adult queens. It is secreted from the mandibular and hypopharyngeal glands of worker bees of the genus Apis mellifera between the sixth and twelfth days of their life ¹⁾. Royal jelly is a food essential for the longevity of the queen bee ²⁾ and it is also fed to all larvae in the colony ³⁾. Royal jelly is a complex substance containing a unique combination of proteins (12-15%), sugars (10-12%), lipids (3-7%), amino acids, vitamins, and minerals ⁴⁾.

The honeybee forms two female castes: the queen and the worker. This dimorphism does not depend on genetic differences but on ingestion of royal jelly ⁵⁾. When worker bees decide to make a new queen, because the old one is either weakening or dead, they choose several small larvae and feed them with copious amounts of royal jelly in specially constructed queen cells. This type of feeding triggers the development of queen morphology, including the fully developed ovaries needed to lay eggs ⁶⁾. Compared with the short-lived and infertile worker bees, the queen bee, which is exclusively fed royal jelly, is characterized by her extended lifespan and her well-developed gonads. Therefore, royal jelly has been long- used as a supplement for nutrition, anti-aging or infertility ⁷⁾.

Royal jelly develops the queen bee gonads. A royal jelly diet induced higher testosterone content and more intensive spermatogenesis in hamster testis ⁸⁾ and increased serum testosterone levels in heat stressed male rabbits ⁹⁾. It may also modulate sex hormones in humans. Dehydroepiandrosterone sulfate (DHEA-S), which declines during normal aging, may serve as a potential longevity marker ¹⁰⁾ and may improve insulin resistance ¹¹⁾. Men with higher serum DHEA-S had a longer life span in a Baltimore longitudinal study of aging male humans ¹²⁾. Estradiol (E2) is more important than testosterone in the pathway to insulin resistance in healthy, young postmenopausal women ¹³⁾.

Royal jelly has been demonstrated (in test tube and animal studies) to possess many pharmacological activities in experimental animals, including antitumor ¹⁴⁾, anti-oxidant ¹⁵⁾, anti-inflammatory ¹⁶⁾, antibacterial ¹⁷⁾, anti-allergic ¹⁸⁾, anti-aging ¹⁹⁾ and antihypertensive properties ²⁰⁾. In humans, its oral ingestion improves lipoprotein metabolism and reduces serum total cholesterol (TC) and low-density lipoprotein (LDL) levels ²¹⁾. Lady 4, a combination of four natural components (evening primrose oil, damiana, ginseng) including royal jelly, promoted health and well-being in postmenopausal women ²²⁾.

Figure 1. Fresh royal jelly surrounding developing queen bee larvae

Royal jelly uses

Royal jelly has long been sold as both a dietary supplement and alternative medicine. Both the European Food Safety Authority ²³⁾ and United States Food and Drug Administration ²⁴⁾ have concluded that the current evidence does not support the claim of health benefits, and have actively discouraged the sale and consumption of the jelly. In the United States, the Food and Drug Administration has taken legal action against companies that have used unfounded claims of health benefits to market royal jelly products. There have also been documented cases of allergic reactions, namely hives, asthma, and anaphylaxis, due to consumption of royal jelly.

Table 1. Royal jelly (fresh) nutrition facts

Royal jelly contains a considerable amount of proteins, free amino acids, sugars, vitamins and sterols, the medium chain fatty acids  10-hydroxy-2-decenoic (10H2DA), 3,10-dihydroxydecanoic (3,10 DDA) and sebacic acids (Figure 2) are major and unique royal jelly components ²⁶⁾. Royal jelly exerts estrogen effects in vitro (test tube) and in vivo (animal) studies, similar to those evoked by 17β-estradiol (Estrogen) ²⁷⁾. Royal jelly competes with 17β
-estradiol (estrogen) for binding to the human estrogen receptors (ERs) α and β, though it is much weaker than diethylstilbestrol in terms of binding affinity ²⁸⁾.

Estrogens play pivotal roles in regulating the function of many tissues and organs and estrogen signaling has been associated with a number of diseases, including breast and uterine cancers, disorders of lipid metabolism, cardiovascular diseases, autoimmune inflammatory diseases, osteoporosis, menstrual abnormalities and infertility ²⁹⁾. Estrogens exert their effects via intracellular receptors, estrogen receptors alpha (ERα) and beta (ERβ) ³⁰⁾. In the presence of ligands, both ERα and ERβ are activated and as dimers interact with specific DNA sequences. Activated estrogen receptors (ERs) interact with other nuclear proteins, such as steroid receptor co-regulators, altering the transcription rates of responsive genes. The activated ERα and ERβ can also bind to other transcription factors, such as activator protein 1 (AP-1) and nuclear factor kappa B (NF-kB), affecting their binding to their cognate DNA sequences and their transcriptional effects ³¹⁾. More recently, the G protein-coupled receptor, GPR30/GPER, has been shown to mediate rapid estrogen effects as well as to regulate transcriptional activation. Possible synergism and antagonism with classical estrogen receptors has been suggested ³²⁾.

Figure 2. Royal jelly active compunds

Note: Structures of 17β-estradiol (17β-E2) = Estrogen, 10-hydroxy-2-decenoic acid (10H2DA), 3,10-dihydroxydecanoic acid (3,10DDA) and sebacic acid (SA)

Royal jelly side effects and adverse reactions

In the literature, several cases of hemorrhagic colitis ³³⁾, asthma ³⁴⁾ and anaphylaxis ³⁵⁾ by ingestion of royal jelly have been reported. Royal jelly should be considered as a causative allergen. Increased consumption of royal jelly in health food supplements may increase incidence of royal jelly-related allergic reactions ³⁶⁾.

Royal jelly may cause allergic reactions in humans ranging from hives, asthma, to even fatal anaphylaxis ³⁷⁾, ³⁸⁾, ³⁹⁾. The incidence of allergic side effects in people who consume royal jelly is unknown. The risk of having an allergy to royal jelly is higher in people who have other allergies ⁴⁰⁾.

What is safflower oil

Safflower (Carthamus tinctorius) is a highly branched, herbaceous, thistle-like annual plant. Safflower is commercially cultivated for vegetable oil extracted from the seeds – safflower oil. Safflower plants are 30 to 150 cm (12 to 59 in) tall with globular flower heads having yellow, orange, or red flowers (see Figure 1). Each branch will usually have from one to five flower heads containing 15 to 20 seeds per head. Safflower is native to arid environments having seasonal rain. It grows a deep taproot which enables it to thrive in such environments.

Traditionally, the safflower crop was grown for its seeds and used for coloring and flavoring foods, in medicines and making red (carthamin) and yellow dyes, especially before cheaper aniline dyes became available. For the last fifty years or so, the plant has been cultivated mainly for the vegetable oil extracted from its seeds.

Safflower seed oil is flavorless and colorless and nutritionally similar to sunflower oil. Safflower oil is used mainly in cosmetics and as a cooking oil, in salad dressing, and for the production of margarine.

There are two types of safflower that produce different kinds of oil: one high in monounsaturated fatty acid (oleic acid) and the other high in polyunsaturated fatty acid (linoleic acid). Currently the predominant edible oil market is for the polyunsaturated fatty acid (linoleic acid), which is lower in saturated fats than olive oil. The latter is used in painting in the place of linseed oil, particularly with white paints, as it does not have the yellow tint which linseed oil possesses.

Oils rich in polyunsaturated fatty acids, notably linoleic acid, are considered to have some health benefits. One human study compared high-linoleic safflower oil with conjugated linoleic acid (CLA), showing that body fat decreased and adiponectin levels increased in obese postmenopausal women with type 2 diabetes mellitus consuming safflower oil ¹⁾. The dietary oil, conjugated linoleic acid (CLA), has reduced body weight and body fat in some clinical studies ²⁾, ³⁾ and animal models ⁴⁾ for diet-induced obesity. Therefore, CLA (conjugated linoleic acid) has been promoted as a weight-loss supplement.

Conjugated linoleic acid (CLA) is a group of polyunsaturated fatty acids found in beef, lamb and dairy products that exist as positional and stereo-isomers of octadecadienoate (18:2) ⁵⁾.

Figure 1. Safflower

Safflower Oil

Safflower oil is available in U.S. grocery stores and is rich in the essential n-6 polyunsaturated fatty acid (PUFA) linoleic acid (LA). Omega-6 polyunsaturated fatty acid (PUFA) are characterized by the presence of at least 2 carbon-carbon double bonds, with the first bond at the sixth carbon from the methyl terminus. Linoleic acid (LA), an 18-carbon fatty acid with 2 double bonds (18:2 omega-6 polyunsaturated fatty acid), is the primary dietary omega-6 PUFA. Linoleic acid cannot be synthesized by humans, and although firm minimum requirements have not been established for healthy adults, estimates derived from studies in infants and hospitalized patients receiving total parenteral nutrition suggest that an linoleic acid intake of ≈0.5% to 2% of energy is likely to suffice. Dietary recommendations for omega-6 PUFAs traditionally focused on the prevention of essential fatty acid deficiency but are now increasingly seeking to define “optimal” intakes to reduce risk for chronic disease, particularly coronary heart disease. The Institute of Medicine’s Food and Nutrition Board, in their Dietary Reference Intake Report for Energy and Macronutrients ⁶⁾, defines an adequate intake of Linoleic acid (LA) as 17 g/d for men and 12 g/d for women (5% to 6% of energy) 19 to 50 years of age, approximately the current median US intake. The average daily intake of linoleic acid for women ages 51–70 in the U.S. is 12.6 g, which equates to 5.7% of energy in a 2,000 kilocalorie diet ⁷⁾.

Other governmental health recommendations for omega-6 fatty acid intakes (on a percent energy basis) are as follows: European Commission, 4% to 8% ⁸⁾; Food and Agriculture Organization/World Health Organization, 5% to 8% ⁹⁾; British Nutrition Foundation, 6% to 6.5% (maximum, 10%) ¹⁰⁾; the Department of Health and Ageing, Australia and New Zealand, 4% to 5% (maximum, 10%) ¹¹⁾; and the American Dietetic Association/Dietitians of Canada, 3% to 10% ¹²⁾. The American Heart Association places primary emphasis on healthy eating patterns rather than on specific nutrient targets.

After consumption, linoleic acid can be desaturated and elongated to form other omega-6 PUFAs such as γ-linolenic and dihomo-γ-linolenic acids. The latter is converted to the metabolically important omega-6 PUFA arachidonic acid (AA; 20:4 omega-6), the substrate for a wide array of reactive oxygenated metabolites. Because linoleic acid accounts for 85% to 90% of the dietary omega-6 PUFA, dietary arachidonic acid [a polyunsaturated omega-6 fatty acid 20:4(ω-6)], which can affect tissue arachidonic acid [a polyunsaturated omega-6 fatty acid 20:4(ω-6)] levels ¹³⁾, may have physiological sequelae. Linoleic acid (LA) comes primarily from vegetable oils (eg, corn, sunflower, safflower, soy). The average US intake of LA, according to National Health and Nutrition Examination Survey 2001 to 2002 data for adults ≥19 years of age, is 14.8 g/d.9 On the basis of an average intake of 2000 kcal/d, LA intake is 6.7% of energy. AA (≈0.15 g/d) is consumed preformed in meat, eggs, and some fish. Numerous health organizations have recommendations for dietary linoleic acid (LA) intake, generally falling within the range of 3–10% of total energy consumption ¹⁴⁾.

Table 1. Safflower oil nutrition facts

Safflower Oil Omega-6 PUFAs and Inflammation

Arguments for reduced Linoleic acid (Omega-6 PUFA) intakes are based on the assumption that because coronary artery disease has an inflammatory component ¹⁶⁾ and because the omega-6 fatty acid, arachidonic acid (AA), is the substrate for the synthesis of a variety of proinflammatory molecules, reducing linoleic acid (Omega-6 PUFA) intakes should reduce tissue arachidonic acid (AA) content, which should reduce the inflammatory potential and therefore lower the risk for coronary heart disease. The evidence, derived primarily from human studies, regarding this line of reasoning is examined below.

Arachidonic acid (AA) is the substrate for the production of a wide variety of eicosanoids (20-carbon AA metabolites). Some are proinflammatory, vasoconstrictive, and/or proaggregatory, such as prostaglandin E2, thromboxane A2, and leukotriene B4. However, others are antiinflammatory/antiaggregatory, such as prostacyclin, lipoxin A4 ¹⁷⁾ and epoxyeicosatrienoic acids ¹⁸⁾. Epoxyeicosatrienoic acids are fatty acid epoxides produced from AA by a cytochrome P450 epoxygenase. Epoxyeicosatrienoic acids also have important vasodilator properties via hyperpolarization and relaxation of vascular smooth muscle cells ¹⁹⁾. Importantly, because the production of AA from LA is tightly regulated ²⁰⁾, wide variations in dietary LA (above minimal essential intakes) do not materially alter tissue AA content ²¹⁾. In tracer studies, the extent of conversion of LA to AA is ≈0.2% ²²⁾.

In studies with vascular endothelial cells, omega-6 PUFA had antiinflammatory properties, suppressing the production of adhesion molecules, chemokines, and interleukins, all key mediators of the atherosclerotic process ²³⁾. In human studies, higher plasma levels of omega-6 PUFAs, mainly AA, were associated with decreased plasma levels of serum proinflammatory markers, particularly interleukin-6 and interleukin-1 receptor antagonist, and increased levels of antiinflammatory markers, particularly transforming growth factor-β ²⁴⁾. When healthy volunteers were given ≈7 times the usual intake of AA (ie, 1.5 g/d) in a 7-week controlled feeding study, no effects on platelet aggregation, bleeding times, the balance of vasoactive metabolites, serum lipid levels, or immune response were observed ²⁵⁾. Likewise, in a recent study from Japan, AA supplementation (840 mg/d for 4 weeks) had no effect on any metabolic parameter or platelet function.19 Consistent with this, in observational studies, higher omega-6 PUFA consumption was associated with unaltered or lower levels of inflammatory markers ²⁶⁾.

Diets high in LA can increase the ex vivo susceptibility of low-density lipoprotein (LDL “bad” cholesterol) to oxidation ²⁷⁾ and oxidized LDL can promote vascular inflammation ²⁸⁾. Therefore, oxidized LDL may play some role in the etiology of coronary heart disease ²⁹⁾. However, the extent of LDL oxidation at higher LA intakes (5% to 15% of energy) has not been established, and its clinical relevance is in question owing to the general failure of antioxidant treatments to mitigate coronary artery disease risk in most randomized trials ³⁰⁾. At present, little direct evidence supports a net proinflammatory, proatherogenic effect of LA in humans ³¹⁾, ³²⁾.

Omega-6 PUFA Consumption and Other Coronary Heart Disease Risk Factors/Markers

The cholesterol-lowering effect of Linoleic acid (Omega-6 PUFA) is well established from human trials. In a meta-analysis of 60 feeding studies including 1672 volunteers, the substitution of PUFA (largely omega-6, varying from 0.6% to 28.8% energy) for carbohydrates had more favorable effects on the ratio of total to high-density lipoprotein cholesterol (perhaps the best lipid predictor of coronary heart disease risk) than any class of fatty acids ³³⁾. Higher plasma PUFA levels are associated with a reduced ratio of total to high-density lipoprotein cholesterol ³⁴⁾, and epidemiologically, the replacement of 10% of calories from saturated fatty acid with omega-6 PUFA is associated with an 18-mg/dL decrease in LDL “bad” cholesterol, greater than that observed with similar replacement with carbohydrate ³⁵⁾. These findings confirm an LDL-lowering effect of omega-6 PUFA beyond that produced by the removal of saturated fatty acids. Favorable effects of Linoleic acid (Omega-6 PUFA) on cholesterol levels are thus well documented and would predict significant reductions in coronary artery disease risk. Additionally, higher Linoleic acid (Omega-6 PUFA) intakes may improve insulin resistance ³⁶⁾ and reduce the incidence of diabetes mellitus ³⁷⁾ and higher serum LA levels are associated with lower blood pressure ³⁸⁾. Nevertheless, not all studies support a beneficial effect of LA on coronary artery disease risk markers. For example, an angiographic study reported a direct association between PUFA intakes and luminal narrowing in women with coronary heart disease ³⁹⁾. However, effects on markers do not always translate into effects on actual clinical end points; thus, it is essential to evaluate the relations between LA consumption and cornary artery disease events.

These observational studies use the strongest designs, minimizing both selection and recall bias. No significant associations between LA or omega-6 PUFA intake and coronary artery disease risk were seen in the Finnish Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study ⁴⁰⁾, Lipid Research Clinics study ⁴¹⁾, or Honolulu Heart Program ⁴²⁾. Modest, nonsignificant inverse associations were observed in the Multiple Risk Factor Intervention Trial ⁴³⁾, the Irish-Boston Heart Study ⁴⁴⁾ and the Health Professionals Follow-Up Study ⁴⁵⁾. In the Health Professionals Follow-Up Study, coronary artery disease rates were lowest in participants with higher intake of both omega-3 and omega-6 PUFAs ⁴⁶⁾ and in the Western Electric Study47 and the Kupio Heart Study ⁴⁷⁾, higher LA intakes or serum levels were associated with lower risk of coronary heart disease or total mortality. In the Nurses’ Health Study, in which diet was assessed multiple times over 20 years ⁴⁸⁾, coronary heart disease risk was ≈25% lower comparing the 95th and 5th percentiles of LA intake (7.0% versus 2.8% of energy, respectively). Most prospective cohort studies have not found significant associations between omega-6 fatty acid intakes and ischemic ⁴⁹⁾ or hemorrhagic ⁵⁰⁾ stroke or stroke mortality ⁵¹⁾. In 1 prospective study, serum LA levels predicted lower risk of stroke, particularly ischemic stroke ⁵²⁾. LA intakes are not associated with risk for cancer ⁵³⁾. Therefore, observational studies generally suggest an overall modest benefit of omega-6 PUFA intake on coronary artery disease risk and no significant effect on stroke or cancer. These studies, some of which included LA intakes of up to 10% to 12% of energy, contradict the supposition that higher omega-6 PUFA intakes increase risk for coronary artery disease.

Several randomized trials have evaluated the effects of replacing saturated fatty acids with PUFAs on coronary artery disease events ⁵⁴⁾. Intakes of PUFA (almost entirely omega-6 PUFA) ranged from 11% to 21%. In addition to the inability to double-blind these studies, many had design limitations such as small sample size (n=54), the provision of only ≈50% of meals, outcomes composed largely of “soft” ECG end points ⁵⁵⁾, randomization of sites rather than individuals with open enrollment and high turnover of subjects, use of vegetable oils that also contained the plant omega-3 fatty acid α-linolenic acid (ALA) ⁵⁶⁾ and simultaneous recommendations to increase fish and cod liver oil use ⁵⁷⁾. Nevertheless, a meta-analysis including 6 of these trials indicated that replacing saturated fatty acids with PUFAs lowered the risk for coronary artery disease events by 24% ⁵⁸⁾. Of the remaining 4 studies, 1 reported a significant 45% reduction in risk ⁵⁹⁾, whereas no significant effect was seen in the others ⁶⁰⁾.

CLA safflower oil

CLA (conjugated linoleic acid) is a natural, but minor, component of fats from ruminant animals that enters the human diet primarily in meat and dairy products ⁶¹⁾. CLA has been shown to have many biological effects, including anticarcinogenisis, antiatherogenesis, immune modulation, and changes in body composition, and is commercially available as an over-the-counter supplement ⁶²⁾. CLA (conjugated linoleic acid) is not a single substance. CLA is a collective term for a class of conjugated dieonic isomers of linoleic acid. It is possible that a number of these CLA isomers have biological activity. However, all of the known physiologic effects of CLA are induced by 2 isomers: c9,t11-CLA and t10,c12-CLA (see Figure 2) ⁶³⁾.

In some cases an effect is produced by one of these isomers acting alone. For example, it is apparent that t10,c12-CLA is solely responsible for the reduction of body fat gain ⁶⁴⁾, whereas the c9,t11-isomer enhances growth and feed efficiency in young rodents ⁶⁵⁾. In other cases the isomers act together to induce an effect. For example, both c9,t11- and t10,c12-CLA appear to be equally effective in inhibiting chemically induced mammary carcinogenesis in rodent models ⁶⁶⁾, in part by inhibiting angiogenesis ⁶⁷⁾, whereas t10,c12-CLA appears to be more effective than c9,t11-CLA in inhibiting the proliferation of MCF-7 breast cancer cells by way of elicitation of a p53 response ⁶⁸⁾. In still other instances the 2 biologically active CLA isomers appear to act in apparent opposition ⁶⁹⁾. Hence, the multiple physiologic effects that are reported for CLA (Table 1 below) appear to be the result of multiple interactions of the biologically active CLA isomers with numerous metabolic signaling pathways ⁷⁰⁾.

Figure 2. CLA (conjugated linoleic acid) isomers

In nature, the most abundant isomer is cis-9,trans-11 (c9,t11), whereas in supplement forms CLA is typically sold as an equal mix of the 2 predominant isomers c9,t11 and t10,c12 ⁷²⁾.

The discovery that CLA inhibited carcinogenesis in several animal models led to an investigation into the biochemical mechanisms of action of CLA. In the course of research of many scientists, a number of additional potential applications were identified, as indicated in Table 2.

The potential use of CLA to control body fat gain in humans and animals has received the most recent attention in both popular and scientific publications.

Table 2. Some of the reported physiologic effects of CLA (conjugated linoleic acid)

CLA and weight loss

Despite the multitude of human clinical trials testing the effect of CLA on body composition, the effect of CLA has been controversial because significant effects of CLA on body fat have not been consistently reported ⁷⁴⁾. An analysis of multiple studies indicates that there is a significant CLA dose effect in humans. In the one human study in which doses were directly compared, however, a dose of 3.4 g/d resulted in a weight loss of 0.14 kg/wk, whereas the 6.8 g/d dose resulted in a weight loss of 0.11 kg/wk ⁷⁵⁾. The failure to show a dose effect in this single study compared with the cumulative data from multiple studies reflects the inherent variability of fat loss in free-living humans. The highest dose provided in a human trial to date is 6.8 g/d (50:50 mixture of the t10, c12 and c9, t11 isomers) ⁷⁶⁾. There is insufficient human data to determine whether higher doses will produce more weight loss. Based on animal studies, it is possible that doses higher than 6.8 g CLA/day would produce additional fat loss. It is difficult to predict, however, because it is not obvious how to scale the doses between mice and humans. In animal studies that showed larger relative effects on fat mass than those we summarize here for human studies, doses have been provided in the range of 0.1% to 1% of the diet as CLA. Based on dose per body weight, these doses in a mouse provide 0.2 to 3 g/kg and are much larger than the 0.015 to 0.1 g/kg doses used in these human studies. On the basis of percentage energy intake, however, the 0.1% to 1% of diet doses in the mouse corresponds to doses between 0.2% and 2% of energy. An effective dose of CLA for loss of weight and adipose in humans may be between 0.5 and 5 g CLA mixed isomers per day ⁷⁷⁾.

Most CLA studies reviewed were ≤12 wk in length. Overall, fat loss was nearly linear for the first 6 mo of treatment and then began decelerate and to approach an asymptote, based largely on the single 2 year study ⁷⁸⁾. In contrast, most control groups would be predicted to gain a small amount of fat mass during a 2-y interval, so preventing gains in fat mass during long-term CLA treatment has a potential health advantage. Unfortunately, this single 2-year study was performed open label and did not include a placebo group for the second year ⁷⁹⁾. Therefore, it is not possible to reach definitive conclusions about potential body-composition benefits of CLA consumption for longer periods of time.

Very few data are available on individual CLA isomers and body composition. The results of the 3 single isomer studies, however, are not inconsistent with animal studies showing the t10, c12 isomer to be the efficacious isomer for body composition ⁸⁰⁾. For most human studies, the t10, c12 isomer was provided as an equal mix with the c9, t11 isomer. There are inadequate data to indicate an ideal mix of isomers for body composition, but the data available to date indicate that a mixture of t10, c12 and c9, t11 results in no severe adverse events, although the one human study that used the t10, c12 isomer alone did result in transient insulin resistance within 12 weeks ⁸¹⁾.

CLA safflower oil safety and side effects

CLA safety has been evaluated in several well-conducted animal toxicologic studies.

Scimeca ⁸²⁾ conducted a 36-wk feeding trial in which Fischer 344 rats were fed either control diet or diet supplemented with 1.5% CLA, a level ≈30 times greater than humans would ingest at 3 g CLA/d. Food disappearance, body weights, cageside examinations, and hematologic and histopathologic analyses of 15 major organs were conducted. No adverse effects were observed.

O’Hagan and Menzel ⁸³⁾ conducted a subchronic 90-d oral rat toxicity study, accompanied by a battery of in vitro genotoxicity studies that are typical for assessment of food ingredient safety, on a commercial preparation of CLA that consisted of equal amounts of the c9,t11- and t10,c12-CLA isomers in the form of glycerides (rather than free fatty acids). They concluded that the no observed adverse effect levels for male and female rats were 2433 and 2728 mg/kg body weight per day, respectively.

In addition to these peer-reviewed published studies, there are 2 abstracts of note that relate to CLA safety assessment in animal models. Schulte et al ⁸⁴⁾ and Pfeiffer et al ⁸⁵⁾ conducted comprehensive toxicologic evaluations of CLA methyl esters in dogs and pigs, using standard toxicologic protocols approved by European Organisation for Economic Co-operation and Development Guidelines. They concluded that CLA methyl esters did not produce adverse effects in these species even when fed at 5% of the diet. These findings should, of course, be considered preliminary until the full-length manuscripts are available for review.

A number of human clinical trials that relate to safety and efficacy were also conducted. In designing human trials, CLA quality is a topmost issue. The most successful clinical studies were conducted with high-quality CLA preparations that consist almost entirely (ie, >90%) of the 2 biologically active isomers (Figure 2 above) in approximately equal amounts (ie, about 45% each), as reviewed by Gaullier et al ⁸⁶⁾. It should also be noted that such high-quality CLA, when consumed at 3–6 g/d, does not appear to induce adverse effects in humans ⁸⁷⁾, ⁸⁸⁾.

Despite these conclusions some researchers have recently raised concerns about the potential safety of CLA for humans ⁸⁹⁾. The concerns include the induction of fatty liver, insulin resistance, and lipodystrophy in mice fed CLA-supplemented diets and in some human trials enhanced C-reactive protein, lipid peroxidation, unfavorable changes in serum lipids, and reduced milk fat.

Fatty liver is induced in mice fed CLA-supplemented diets [Pariza et al ⁹⁰⁾]. However, this finding appears limited to mice in that it has not been reported for other species. Hamsters fed CLA and female rats fed diet supplemented with 15% CLA also exhibit enlarged livers, but this result is due to hypertrophy, not fat accumulation ⁹¹⁾. It should be noted that neither fatty liver nor liver hypertrophy is considered by toxicologists to be a toxic effect ⁹²⁾. O’Hagan and Menzel ⁹³⁾ reported that the liver hypertrophy observed in female rats fed diet supplemented with 15% CLA was completely reversible when the animals were switched to a diet free of CLA.

CLA has also been reported to increase insulin resistance ⁹⁴⁾, ⁹⁵⁾. This has been most notable in studies of short duration ⁹⁶⁾, those that used single isomers ⁹⁷⁾, ⁹⁸⁾, or both. For example, in one study, insulin resistance was reported in individuals supplemented with only the t10, c12 isomer for 12 wk, but not with a mixed preparation of predominantly the c9, t11 and t10, c12 isomers ⁹⁹⁾. In a later study, the same enriched t10, c12 supplement was given for 18 wk and did not result in insulin resistance ¹⁰⁰⁾. Many studies either have not found significant changes in fasting glucose or insulin or in measures of insulin sensitivity ¹⁰¹⁾, ¹⁰²⁾ or have found an improvement ¹⁰³⁾. With regard to both safety and efficacy, it has been suggested that CLA preparations enriched in c9, t11 and t10, c12 isomers are preferable to preparations containing 4 isomers ¹⁰⁴⁾, and this may also be true compared with single isomer preparations. Further investigation into the safety of CLA is warranted.

A related effect, lipodystrophy, was reported in mice fed a diet supplemented with CLA. Like fatty liver, lipodystrophy has not been reported to occur in other species, and it is possible that lipodystrophy is seen in mice because mice are so sensitive to CLA-induced body fat reduction. Increasing the amount of fat in CLA-supplemented diet substantially reduces the lipodystrophy effect ¹⁰⁵⁾.

With regard to these seemingly negative effects, it should be noted that dietary CLA significantly extended the life span of NZB/WF1 mice, which are prone to developing lupus erythematosus ¹⁰⁶⁾. This finding is consistent with the conclusion that CLA does not induce toxic effects and is important because mice appear to be the most sensitive and responsive known species to the effects of CLA on lipid metabolism ¹⁰⁷⁾.

Concern about elevations in oxidative stress and unfavorable changes in blood lipids has arisen from studies by Riserus et al ¹⁰⁸⁾ who investigated the effects of CLA in men with metabolic syndrome. They compared a typical high-quality CLA preparation consisting of equal amounts of c9,t11- and t10,c12-CLA with a supplement that is not commercially available, enriched for t10,c12-CLA but containing very little c9,t11-CLA. Riserus et al ¹⁰⁹⁾ observed evidence of enhanced lipid peroxidation (measured as urinary isoprostane), enhanced C-reactive protein in serum, and elevated VLDL coupled with reduced HDL. These negative effects were significant relative to placebo for the patients taking the t10,c12-CLA supplement but were reduced (in some cases below statistical significance) for patients taking the typical commercially available CLA supplement relative to placebo. Interestingly, the apparent t10,c12-CLA-induced oxidative stress did not result in reduced blood antioxidants but rather was correlated with increased blood vitamin E.

Riserus et al ¹¹⁰⁾ concluded that these findings indicate that CLA could enhance inflammation and cardiovascular disease risk. However, other groups that have studied this issue have concluded that CLA reduces inflammation. For example, pigs fed a commercial mixture of CLA isomers displayed reduced inflammation ¹¹¹⁾, and dietary CLA not only reduced atherosclerosis in animal models ¹¹²⁾ but also reduced preestablished atherosclerotic lesions in rabbits ¹¹³⁾ and mice ¹¹⁴⁾. Additionally, the researchers of a comprehensive clinical study of the effects on serum lipids of a high-quality CLA preparation consisting of c9,t11- and t10,c12-CLA in approximately equal amounts concluded, “The study confirms that some of the cardioprotective effects of CLA that were shown in animal studies are relevant to man” ¹¹⁵⁾.

Riserus et al ¹¹⁶⁾ also reported that the men in their study who were given the t10,c12-CLA supplement exhibited enhanced insulin resistance. Again, there was no significant difference in this condition between the placebo group and the group receiving the typical commercially available high-quality CLA isomer mixture, a finding that is also consistent with a previous report from Riserus’s group ¹¹⁷⁾. Evidence of enhanced insulin resistance has not been observed in other CLA clinical trials either ¹¹⁸⁾, ¹¹⁹⁾.

It is well documented that t10,c12-CLA reduces milk fat. This effect has been most thoroughly studied in cows ¹²⁰⁾ but is also observed in lactating women who consume CLA supplements ¹²¹⁾. The researchers of the latter study ¹²²⁾ concluded that the reduction of milk fat might lead to less energy availability for the nursing infant. However, in a study with rats ¹²³⁾ it was found that the pups nursing dams fed CLA-supplemented diet actually grew to a larger body size. Because very little t10,c12-CLA carries over to milk, whereas the c9,t11-CLA isomer is concentrated in milk, it could be concluded that c9,t11-CLA could be a growth factor for young rats, as it appears to be for young mice ¹²⁴⁾. Similar findings were obtained in a study with pigs in which the researchers concluded, “Irrespective of the dietary fat supplied in the starter period, piglets reared on the CLA sows had greater final body and warm carcass weights (P <0.01), and greater feed intake (P = 0.02) than piglets reared on the [control] sows” ¹²⁵⁾. It seems likely that in these studies ¹²⁶⁾ nursing animals compensated for reduced calories because of milk fat reduction by consuming more milk.