What is maca root
Maca (Lepidium meyenii) is a Peruvian plant of the Brassicaceae (mustard) family cultivated for more than 2000 years, which grows exclusively in the central Andes between 4000 and 4500 m altitude 1). Preparations from maca root has been used for centuries in the Andes for nutrition and to enhance fertility and improve sexual function in humans and animals 2), 3), 4).
Figure 1. Maca root
Preparations from the maca root have been reported to improve sexual function in healthy populations 5). Although maca is a plant extract and not a drug, it is one of the most commonly cited “natural drugs” on the Internet for the improvement of sexual desire 6). The hypothesis that maca root may be effective in improving sexual function is supported by several lines of evidence. Animal experiments suggest that maca has spermatogenic and fertility-enhancing activities, which are likely due to the phytosterols or phytoestrogens present in the maca 7). Several animal studies have shown that maca may improve sexual behaviour and enhance androgen-like effects in rats 8). Recent clinical trials have also suggested significant effects of maca for increasing sperm count and mobility and improving sexual function in humans 9), 10). The potential bioactive ingredients in maca include macaridine, macamides, macaene, gluosinolates, maca alkaloid, and maca nutrients 11). However, these data are insufficient for determining whether maca is clinically effective.
There are strong indications 12), 13) that the therapeutic properties of Peruvian Maca and its fertility-enhancing properties in particular, may be linked to high concentrations of Glucosinolates (benzyl and p-methoxybenzyl glucosinolate and their isothiocyanate derivatives), which represent one of the major functional groups of biologically active compounds in this herb 14), 15). It has been further observed that several Glucosinolates’ concentrations determined in hypocotyls of various coloured Maca phenotypes 16), may be linked to specific gender-and age-dependent physiological and therapeutic properties induced by oral administration of Maca preparations, as demonstrated in a series of studies on laboratory animals 17), and on humans using both male subjects 18) and pre- and post-menopausal women 19). It has been further found that the Maca phenotype characterised by the colour Red, has a selective therapeutic functionality affecting men after 50, with a capacity to prevent and reduce prostate hyperplasia 20). Black Maca phenotype was found as having a positive effect on sexual desire, aphrodisiac and fertility-enhancing properties in adult healthy men 21). On the other hand, Yellow based Peruvian Maca in a mix with other phenotypes in a traditionally-harvested Maca crop, had a positive hormone-balancing effect on pre- and post-menopausal women 22) thereby showing potential as a non-hormonal alternative to hormone replacement therapy (HRT) treatment.
As yet there is no clear understanding as to which precisely-defined chemical class or group of compounds, are actually responsible for the medicinal functionality of specific phenotypes of Peruvian Maca with their gender- and age-linked activity. Many of the reported compound classes in plants other that Maca have medicinal functionality such as Catechins from Green tea (Camellia sinensis) which are known for their high anti-oxidant value, Amides in Echinacea species which are associated with the immunomodulatory functions of this herb, Carbolines, containing well known MAO (monoaminooxidase) inhibitors having direct effect on hormone metabolism with various effects on sexual function in animals and Glucosinolates and their derivatives (isothiocyanates, sulphoraphane) in Maca and other Brassica species, which are generally acknowledged to be of therapeutic importance.
Few randomized clinical trials have tested the effects of maca root on sexual function. This review 23) found limited evidence from four small trials that suggested that maca is effective in improving sexual desire after at least 6 weeks. The extent to which the therapeutic effects of maca depend on the type of maca used and the amount of various constituents in the preparation is unclear. The total number of trials, the total sample size, and the average methodological quality of the primary studies were too limited to draw firm conclusions. The optimum dose of maca is unknown. Single-dose studies used extract quantities ranging from 1.5 g/day to 3.0 g/day. A study was not included in the systematic review because no placebo effect was assessed 24). In such study, maca was administered in two doses (1.5 g/day and 3–0 g/day) to patients with selective-serotonin reuptake inhibitor (a group of antidepressant)-induced sexual dysfunction. The Arizona Sexual Experience Scale (ASEX) and the Massachusetts General Hospital Sexual Function Questionnaire (MGH-SFQ) were used to measure sexual dysfunction. Subjects on 3.0 g/day maca had a significant improvement in ASEX and in MGH-SFQ scores, but subjects on 1.5 g/day maca did not. Libido improved significantly based on ASEX item number 1, but not by dosing groups. Maca was well tolerated 25). But the results of that study failed to show differences between the two doses 26). The review authors concluded that more rigorous studies are required to identify the optimal dose.
In another systematic review 27) on the effect of maca root and menopausal symptoms in women, found very few rigorous trials of maca for menopausal symptoms. The results of that systematic review provided limited evidence for the effectiveness of maca as a treatment for menopausal symptoms. The review authors stated that the total number of trials, the total sample size, and the average methodological quality of the primary studies, were too limited to draw firm conclusions. Furthermore, the safety of maca root has not been proven yet 28). They added that the efficacy of maca root on women menopausal symptoms and safety should be tested in larger studies.
Maca Root and Sexual Function
Sexual dysfunctions are highly prevalent in our society worldwide, and the occurrence of sexual dysfunctions increases directly with age for both men and women 29). They occur in 20–30% of men and 40–45% of women according to 18 descriptive epidemiological studies from around the world 30).
Most sexual problems relate to sexual desire (interest in sex) in both females and males and male erectile dysfunction (ED) 31). Interest in medicinal plants to treat sexual dysfunctions has increased in the last 20 years 32).
Maca has been described to improve sexual behavior in experimental animals, although conflictive results have been observed 33). Traditionally maca has been referred to as a plant to improve fertility and as an energizer. In a randomized study 34), researchers were unable to demonstrate effect of maca on penile erection in apparently healthy adult men after 12 weeks of treatment with gelatinized maca compared with results using placebo.
Recently, a systematic review has been performed on effect of maca on sexual function in humans 35). In that review, according to the authors only four randomized clinical trials met all the inclusion criteria.
According to the review, two randomized clinical trials suggested a significant positive effect of maca on sexual dysfunction or sexual desire in healthy menopausal women 36) or healthy adult men 37), respectively, while the other randomized clinical trials according to the reviewers failed to show any effects in healthy cyclists. However, analyzing results from such study, authors showed that maca extract significantly improved the self-rated sexual desire score compared to the baseline test and compared to the placebo trial after supplementation 38). The effect in this study was as early as 14 days of treatment which is significantly shorter that that showed with gelatinized maca in which effects were observed after 8 weeks of treatment.
A further randomized clinical trial assessed the effects of maca in patients with mild erectile dysfunction using the International Index of Erectile Dysfunction-5 and showed significant effects on subjective perception of general and sexual well-being 39).
Although evidence suggests an effect of maca on sexual desire and mild erectile dysfunction data also revealed that maca extract seems to have better effect 40) than gelatinized maca 41) and that of maca flour. The difference seems to be due to the fact that extract allow the concentration the secondary metabolites.
In summary, there is evidence that maca may improve sexual desire but is inconclusive an effect on erectile function.
Maca and Sperm Function
In a study in 9 apparently healthy men who had received maca for 4 months showed an increase in seminal volume, sperm count, and sperm motility 42). Serum hormone levels (LH, FSH, prolactin, estradiol, and testosterone) in men were not affected by treatment with maca 43).
Maca powder and maca extract were unable to activate androgen receptor-mediated transcription in prostate cancer cell lines 44) or in a yeast-based hormone-dependent reporter assay 45).
In summary, experimental and one clinical studies suggest that consumption of maca is associated with an increase in sperm count.
Maca as an Energizer
Maca has been shown to reduce scores in depression and anxiety inventories 46). A self-perception survey showed that maca acted as energizer compared with placebo in apparently healthy men 47).
Maca extract administration for 14 days significantly improved 40 km cycling time performance compared to the baseline test, but not compared to the placebo trial after supplementation.
In summary, scientific evidences suggest that maca may be an energizer.
Maca and Metabolic Syndrome
One study has been reported on effects of maca alone or combined with another supplements in patients with metabolic syndrome. The randomized placebo-controlled 90-day study assessed the effects of maca and yacon in combination with silymarin on plasma and lipoprotein lipids, serum glucose, and safety parameters in patients suffering from the metabolic syndrome.
No adverse effects were found in volunteers using silymarin (0.8 g/day), silymarin + yacon (0.8 + 2.4 g/day), and silymarin + maca (0.6 + 0.2 g/day). A moderate AST level and diastolic blood pressure increase was found in volunteers using maca (0.6 g/day) 48).
However, a randomized clinical trial in healthy men showed that gelatinized maca reduced systolic and diastolic blood pressure after 12 weeks of treatment 49). Moreover, maca significantly inhibited the hypertension relevant angiotensin I-converting enzyme (ACE) in vitro 50).
In a population traditionally consuming maca, systolic blood pressure was lower than in those not consuming maca 51). Similarly, AST (aspartate aminotransferase – is usually used to detect liver damage) levels were similar in those consuming and those not consuming maca 52).
Maca contains high amounts of potassium 53). Potassium is an important nutrient to reduce risk of hypertension 54) and as a primary metabolite may be useful in patients with hypertension. In addition other secondary metabolites may be also be active to reduce blood pressure 55).
Maca and Osteoarthritis
In a randomized double-blind study on 95 patients with osteoarthritis, a combination of Uncaria guianensis (cat’s claw; 300 mg) and maca (1,500 mg) was administered twice a day for 8 weeks and compared with a treatment with glucosamine sulfate. Both treatments substantially improved pain, stiffness, and functioning in the patients 56). However, as the study did not include a placebo control group, glucosamine effects remain unclear.
Maca root dangers and side effects
Maca has been used for centuries in the Central Andes of Peru, and no toxic effects have been reported if it was consumed after boiling 57). Previous review data on in vivo and in vitro studies with maca indicate that its use is safe 58). Further evidence shows that aqueous and methanolic extracts of maca do not display in laboratory test tube on liver cell toxicity study 59). Moreover, freeze-dried aqueous extract of maca (1 g/kg body weight) in mice did not reveal any toxic effect on the normal development of preimplanted mouse embryos 60).
Results in rats show that different types of maca (black, red, and yellow) have no acute toxicity at ≤17 g of dried hypocotyls/kg body weight. Rats treated chronically for 84 days with 1 g/Kg body weight showed no side effects and a histological picture of liver similar to that observed in controls 61). As usual doses in rats are 1-2 g/Kg body weight, it is suggested that maca is safe. Human consumption of ≤1 g/kg per day is considered safe, as well. However, as referred above in a study in patients with metabolic syndrome the administration of maca at a dose of 0.6 g/day for 90 days resulted in a moderate elevation of AST (aspartate aminotransferase – is usually used to detect liver damage) and diastolic arterial pressure 62). This has not been confirmed in other studies 63). Data on population of 600 subjects in the Peruvian central Andes showed that maca consumption was safety and that health status was improved 64).
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