hibiscus-tea

What is hibiscus tea good for

Hibiscus tea (Hibiscus sabdariffa L. tisane) is a herbal tea made as an infusion from crimson or deep magenta-colored Hibiscus sabdariffa calyces (see Figure 1) (sepals) of the roselle (Hibiscus sabdariffa) flower. Hibiscus tea is consumed both hot and cold. Hibiscus tea is one of the most common ingredients found in commercial herbal tea (tisane) blends sold in the US 1). In other parts of the world, Hibiscus sabdariffa calyces (see Figures 1 and 2) and beverages derived from them, are called hibiscus tea, bissap, roselle, red sorrel, agua de Jamaica, Lo-Shen, Sudan tea, sour tea, or karkade. Hibiscus sabdariffa decoctions and infusions of calyxes (hibiscus tea), and on occasion Hibiscus leaves, are used in at least 10 countries worldwide in the treatment of hypertension and hyperlipidemia with no reported adverse events or side effects. In test tube studies show that Hibiscus sabdariffa has antioxidant properties 2)3) and, in animal models, extracts of Hibiscus sabdariffa flower have demonstrated hypocholesterolemic 4) and antihypertensive properties 5). Concentrated Hibiscus sabdariffa beverages lower blood pressure (BP) 7 in patients with hypertension 6) and type 2 diabetes 7) compared with black tea (Camelia sinensis) and have an effect similar to common hypotensive drugs 8).

Table 1. Hibiscus sabdariffa raw (Roselle) nutrition facts

NutrientUnitValue per 100 g
Approximates
Waterg86.58
Energykcal49
EnergykJ205
Proteing0.96
Total lipid (fat)g0.64
Ashg0.51
Carbohydrate, by differenceg11.31
Minerals
Calcium, Camg215
Iron, Femg1.48
Magnesium, Mgmg51
Phosphorus, Pmg37
Potassium, Kmg208
Sodium, Namg6
Vitamins
Vitamin C, total ascorbic acidmg12
Thiaminmg0.011
Riboflavinmg0.028
Niacinmg0.31
Vitamin B-12µg0
Vitamin A, RAEµg14
Retinolµg0
Vitamin A, IUIU287
Lipids
Fatty acids, total transg0
Cholesterolmg0
[Source: United States Department of Agriculture Agricultural Research Service 9)]

Table 2. Hibiscus tea brewed nutrition facts

NutrientUnitValue per 100 g
Approximates
Waterg99.58
Energykcal0
EnergykJ0
Proteing0
Total lipid (fat)g0
Ashg0.42
Carbohydrate, by differenceg0
Fiber, total dietaryg0
Sugars, totalg0
Sucroseg0
Glucose (dextrose)g0
Fructoseg0
Lactoseg0
Maltoseg0
Galactoseg0
Minerals
Calcium, Camg8
Iron, Femg0.08
Magnesium, Mgmg3
Phosphorus, Pmg1
Potassium, Kmg20
Sodium, Namg4
Zinc, Znmg0.04
Copper, Cumg0
Manganese, Mnmg0.477
Selenium, Seµg0
Vitamins
Vitamin C, total ascorbic acidmg0
Thiaminmg0
Riboflavinmg0
Niacinmg0.04
Pantothenic acidmg0
Vitamin B-6mg0
Folate, totalµg1
Folic acidµg0
Folate, foodµg1
Folate, DFEµg1
Choline, totalmg0.4
Vitamin B-12µg0
Vitamin B-12, addedµg0
Vitamin A, RAEµg0
Retinolµg0
Carotene, betaµg0
Carotene, alphaµg0
Cryptoxanthin, betaµg0
Vitamin A, IUIU0
Lycopeneµg0
Lutein + zeaxanthinµg0
Vitamin E (alpha-tocopherol)mg0
Vitamin E, addedmg0
Vitamin D (D2 + D3)µg0
Vitamin DIU0
Vitamin K (phylloquinone)µg0
Lipids
Fatty acids, total saturatedg0
04:00:00g0
06:00:00g0
08:00:00g0
10:00:00g0
12:00:00g0
14:00:00g0
16:00:00g0
18:00:00g0
Fatty acids, total monounsaturatedg0
16:1 undifferentiatedg0
18:1 undifferentiatedg0
20:01:00g0
22:1 undifferentiatedg0
Fatty acids, total polyunsaturatedg0
18:2 undifferentiatedg0
18:3 undifferentiatedg0
18:04:00g0
20:4 undifferentiatedg0
20:5 n-3 (EPA)g0
22:5 n-3 (DPA)g0
22:6 n-3 (DHA)g0
Fatty acids, total transg0
Cholesterolmg0
Other
Alcohol, ethylg0
Caffeinemg0
Theobrominemg0
[Source: United States Department of Agriculture Agricultural Research Service 10)]

Figure 1. Hibiscus sabdariffa calyces

hibiscus tea

Figure 2. Dried hibiscus calyces

Dried hibiscus

Figure 3. Hibiscus tea

Hibiscus teaHealth benefits of hibiscus tea

Hibiscus sabdariffa (hibiscus tea) is consumed as a beverage in the United States 11), Mexico 12), Nigeria and other West African countries 13), 14), Egypt 15), Iran 16), India 17), Thailand 18) and Tawian 19), among other countries. Ethnomedicinal studies have reported the use of Hibiscus sabdariffa for the treatment of various cardiovascular risk factors including hypertension in Egypt, Jordan, and Trinidad and Tobago 20)21), hypotension in Jordan and Iraq 22), hyperlipidemia in Jordan, Greece, Brazil, and Trinidad and Tobago 23), 24), and obesity in Iraq, Greece, and Brazil 25), 26).

The flowers (Figure 3), or more specifically the Hibiscus sabdariffa calyxes (Figure 1), are typically prepared using an aqueous decoction or infusion 27). However, the Bedouins in the North Badia region of Jordan use the Hibiscus sabdariffa leaves, as well as the flowers, and they drink the infusions hot when treating high blood pressure and cold when treating low blood pressure 28). In Trinidad and Tobago only the Hibiscus sabdariffa leaves are used to treat high blood pressure and the flower and seeds are used to treat high cholesterol 29). Dosing was only described in 1 of the 7 ethnobotancial studies reviewed 30). Mati and colleagues 31) discovered that herbalists in the Kurdistan Autonomous Region of Iraq recommend drinking 1 cup/day of an infusion of 1 tsp (1/2 tsp when ground) of Hibiscus sabdariffa flowers in 1 cup warm water for the treatment of hypotension and 2 cups/day of a decoction of 2 tsp of the Hibiscus sabdariffa flowers in 1/2 L of water or 1 cup/day of a decoction of 50 g in 2 cups of water for the treatment of obesity.

Ethnomedicinal studies provide evidence for the widespread use of a tea made with Hibiscus sabdariffa calyxes to treat hypertension and hyperlipidemia, but these studies provide little guidance for animal and human studies through their lack of attention to cultivation, preparation, and consumption patterns. Animal studies have consistently shown that consumption of Hibiscus sabdariffa extract reduces blood pressure in a dose dependent manner. They have also shown that total cholesterol, LDL “bad” cholesterol, and triglycerides were lowered in the majority of normolipidemic, hyperlipidemic, and diabetic animal models, whereas HDL “good” cholesterol was generally not affected by the consumption of Hibiscus sabdariffa extract.

Hibiscus tea blood pressure

In a randomized, double-blind, placebo-controlled clinical trial 32) involving 65 prehypertensive and mildly hypertensive adults, age 30–70 years, not taking blood pressure (BP)-lowering medications, with either 3 X 240-mL servings/day of brewed hibiscus tea or placebo beverage for 6 week. The study found that daily consumption of 3 servings of Hibiscus sabdariffa (hibiscus) tea, an amount readily incorporated into the diet, effectively lowered blood pressure in pre-hypertensive and mildly hypertensive adults 33). The maximum hypotensive effect was observed after a few weeks of 3 servings of Hibiscus sabdariffa (hibiscus) tea. However, further research is warranted to understand the relative contributions of the acute and chronic actions of hibiscus tea.

The blood pressure-lowering effects of hibiscus tea observed in that study 34) were greater than those reported in 2 large dietary interventions, the Dietary Approaches to Stop Hypertension (DASH) 35) and PREMIER 36) trials, both of which included participants with baseline blood pressure measures similar to this study volunteers. After 8 wk of consuming a diet rich in fruits and vegetables, the difference in systolic blood pressure between the placebo and treatment groups in the DASH study was 2.8 mm Hg, whereas after consuming the combination diet rich in fruits and vegetables plus low-fat dairy products, this difference was 5.5 mm Hg. After 6 months, participants in the PREMIER study given established lifestyle advice (i.e. lose weight, increase physical activity, and reduce sodium and alcohol consumption) lowered their systolic blood pressure by 3.7 mm Hg greater than those given more general advice (control group), whereas participants who were given the established advice and followed the DASH diet lowered their systolic blood pressure by 4.3 mm Hg compared with the control group. In a study, the difference in systolic blood pressure between the placebo and hibiscus tea groups was 5.9 mm Hg, similar to the systolic blood pressure-lowering effect obtained by following the combination DASH diet for 8 weeks. Effects of this magnitude are considered important for public health 37). On a population basis, a 5-mm Hg reduction in systolic blood pressure would result in a 14% overall reduction in mortality due to stroke, a 9% reduction in mortality due to coronary heart disease, and a 7% reduction in all-cause mortality 38). Although the health benefits of following the dietary pattern described in the DASH and PREMIER trials are substantiated, consumers may find these dietary changes too complex or difficult to comply with in full. In contrast, adding hibiscus tea to each meal is simple and, as such, may be an effective strategy for controlling blood pressure among pre-hypertensive and mildly hypertensive adults. Future research should consider whether combining the DASH diet with daily hibiscus tea consumption confers a greater reduction in blood pressure than either approach alone.

Table 3. Hypertension and Hibiscus sabdariffa randomized clinical trials and effects on systolic blood pressure and diastolic blood pressure

Primary
author, year
ConditionSample sizeSubstancePlant partExtract modeDose# of doses per dayDays dose takenMean change in SBP (SD)Within group p-valueMean change in DBP (SD)
McKay, 2010 39)Hypertension31(30)AHFCW1.2/240a3421.3 (10.0)NS0.5 (7.5)
McKay, 2010 40)Hypertension35(35)HSCW2.25/240b3427.2 (11.4)Red3.1 (7.0)
Haji, 1999 41)Hypertension40(23)BTLW2/1c1126.3 (7.7)Red3.5 (6.0)
Haji, 1999 42)Hypertension40(31)HSN/AW2/1c11217.6 (6.8)Red10.9 (5.4)
Mozaffari-Khosravi, 2009 43)Hypertension, Diabetes30(26)BTLW2/240b2308.4 (11.0)Inc4.6 (11.8)
Mozaffari-Khosravi, 2009 44)Hypertension, Diabetes30(27)HSCW2/240b23015.4 (7.5)Red4.3 (12.3)
Herrera-Arellano, 2004 45)Hypertension37(32)Meda25d22816.4 (9.6)Red13.1 (7.2)
Herrera-Arellano, 2004 46)Hypertension53(38)HSCW9.62e12814.2 (11.8)Red11.2 (6.9)
Herrera-Arellano, 2007 47)Hypertension93(N/A)Medb10d12823.3 (7.0)Red15.4 (6.0)
Herrera-Arellano, 2007 48)Hypertension100(N/A)HSCW250e12817.1 (10.0)Red12.0 (7.0)

Notes:

Condition: Hyper=hypertension, Diab=diabetes; Sample size= beginning of study (end of study), N/A=not available;

Substance: HS=Hibiscus sabdariffa, AHFC=artificial hibiscus flavor concentrate, BT=Black tea, Med=blood pressure medication,

aCaptopril,
bLispinopril; Plant part used in extract=F=flower, C=calyx, P=petal L=leaf; Extract mode: W=water, A=alcohol;

Dose: a=mL substance/mL extraction substance;

bg substance/mL extraction substance,
cspoonfuls of substance/glass of extraction substance,
dmg of substance,
emg total anthocyanins; SBP=Systolic blood pressure, DBP=Diastolic blood pressure, SD=standard deviation; Results: NS=not significant,

Dep=depressed, a=more than comparator,

bless than comparator, Ele=elevated, Red=reduced, Inc=increased, depressed or elevated used accordingly when values compared with appropriate control, increased or reduced used when values compared between baseline and end of treatment within the same group
[Source 49)]

The potential mechanisms of action for the blood pressure-lowering effect of hibiscus tea were shown in laboratory test tube and animal studies that show that Hibiscus sabdariffa is a blood vessels relaxant 50), perhaps via action on calcium channels 51), an Angiotensin converting enzyme inhibitor (ACE inhibitor is medicine used in the treatment of hypertension and congestive heart failure) 52), and a diuretic 53). The angiotensin converting enzyme inhibitor activity and natriuretic effects of Hibiscus sabdariffa have also been observed in human studies 54). Other potential mechanisms of action related to the effects of the anthocyanins present in Hibiscus sabdariffa are also possible 55).

 

Table 4. Major phenolic components and antioxidant activity per serving of Hibiscus sabdariffa tea

Component Hibiscus tea 
unit/240 mL
Total phenols, mg gallic acid equivalents21.85
Total anthocyanins, mg CGE7.04
Delphinidin-3-sambubioside, mg CGE3.69
Cyanidin-3-sambubioside, mg CGE0.02
ORAC, μmol trolox equivalents1950

Note: CGE = Cyanidin glucoside equivalents; Antioxidant capacity analyzed using the ORAC assay

[Source 56)]

The observed hypertensive-lowering effect of hibiscus tea could be due to its major flavonoid components, delphinidin-3-sambubioside and cyanidin-3-sambubioside. However, other phytochemicals present might also contribute to this effect 57). Herraro-Arellano et al. 58) demonstrated the blood pressure-lowering effects of a standardized Hibiscus sabdariffa extract containing 250 mg of these anthocyanins in a 4-week study of 171 hypertensive patients. The Hibiscus sabdariffa extract lowered blood pressure from baseline after 4 week, although the magnitude of this effect was lower than that achieved in the comparison group treated with 10 mg lisinopril (a medicine used to lower blood pressure). Other bioavailability studies show that anthocyanins are rapidly absorbed and eliminated and that they are absorbed with poor efficiency 59).

Previous studies conducted in hypertensive patients used a higher dose of Hibiscus sabdariffa to compare its effects with that of either black tea 60) or a hypotensive drug 61). Haji Faraji and Haji Tarkhani 62) tested 54 patients, mean age 52 years, in a hospital-based, randomized, clinical trial over a 15-days period. In their study, the treatment group consumed 1 glass daily of Hibiscus sabdariffa tea prepared with 2 spoonfuls of blended tea per glass brewed in boiling water for 20–30 min. No quantitative analysis of the potential active ingredients in the Hibiscus sabdariffa beverage was reported, although it can be assumed that the higher quantity of dried Hibiscus sabdariffa calyces used in their study, and the longer brew time. Their control group consumed black tea prepared similarly. Black tea is not an inert placebo because it contains caffeine, catechins, and flavonols, compounds known to affect vasodilation. Herrera-Arellano et al. 63) compared Hibiscus sabdariffa with an angiotensin converting enzyme (ACE) inhibitor in a randomized trial of 75 patients aged 30–80 years. In their study, an infusion prepared with 10 g of dry Hibiscus sabdariffa calyces in 0.5 L water (9.6 mg anthocyanins) and administered daily was compared with 25 mg captopril administered twice daily for 4 week and systolic blood pressure did not differ between the groups. The magnitude of change in systolic blood pressure from baseline in both the Haji Faraji and Haji Tarkhani 64) and Herrera-Arellano et al. 65) studies was approximately double the amount observed. This outcome was not unexpected, because the participants in these nonplacebo–controlled studies had higher initial systolic blood pressure (+10–30 mm Hg) and diastolic blood pressure (+12–22 mm Hg) and were taking antihypertensive medication prior to the intervention.

Wahabi et al in a more recent 2015 systematic review on the effectiveness of Hibiscus sabdariffa in the treatment of hypertension 66) found no reliable evidence to recommend Hibiscus sabdariffa as a treatment for primary hypertension in adults. The four randomized controlled studies identified in this review 67) with a total of 390 patients, two studies compared Hibiscus sabdariffa to black tea; one study compared it to captopril and one to lisinopril. The studies found that Hibiscus had greater blood pressure reduction than tea but less than the ACE-inhibitors. However, all studies, except one, were short term and of poor quality with a Jadad scoring of <3 and did not meet international standards. Based on available conflicting evidence, more studies are needed before Hibiscus sabdariffa can reliably be recommended for the treatment of primary hypertension in adults.

Hibiscus sabdariffa and high cholesterol

The clinical study populations were diverse and included healthy people as well as those with metabolic syndrome 68), hyperlipidemia 69), hypertension 70), or type 2 diabetes 71) (Table 5). The study designs compared different doses of Hibiscus sabdariffa 72) or compared Hibiscus sabdariffa to black tea 73), diet and a combination of Hibiscus sabdariffa and diet 74) or a placebo 75). In two studies the dried calyxes of Hibiscus sabdariffa were prepared and administered as a tea 76), 77) and in the other studies fresh calyxes 78), 79) or leaves 80) were prepared as a standardized powdered extract and administered in capsules. The doses of Hibiscus sabdariffa per serving and the frequency of administration varied from .015 g of dried calyxes prepared in water and administered twice daily 81) to 450 g of dried calyxes prepared in water and administered up to 3 times a day 82). Alcohol extractions formulated with 500 g of fresh calyxes were administered once daily 83) and alcohol extracts made from 60,000 g of fresh leaves were administered twice daily 84). The duration of the studies ranged from 15 days 85) to 90 days 86) with most lasting one month.

The effect of Hibiscus sabdariffa on total cholesterol varied. One brief 15 day study reported a significant increase in total cholesterol among hypertensive patients administered Hibiscus sabdariffa 87). In this same study, HDL “good” cholesterol increased and triglyceride and LDL “bad” cholesterol values remained unchanged. Of the remaining 4 studies, one showed no significant change in total cholesterol and the month long studies showed significant decreases in total cholesterol among participants with hypertension, metabolic syndrome and those receiving the two lower doses of Hibiscus sabdariffa 88), 89), 90). Hibiscus sabdariffa significantly increased beneficial HDL “good” cholesterol levels in participants with and without metabolic syndrome 91) and hypertension 92). LDL “bad” cholesterol was significantly decreased as a result of the consumption of Hibiscus sabdariffa in participants with metabolic syndrome 93), hyperlipidemia 94) and type 2 diabetes 95). Triglyceride levels were significantly decreased by Hibiscus sabdariffa in participants with hyperlipidemia 96), type 2 diabetes 97), and without metabolic syndrome 98).

Most studies did not make clear the type of randomized clinical trial being conducted and in many cases there were study design problems. In several randomized clinical trials black tea was used as the comparator, as opposed to a placebo, making the results difficult to interpret because of the active pharmacological properties of black tea. McKay and colleagues’ 99) in the only placebo-controlled trial to date provided a notable exception to this trend by using a placebo drink that was non-active and is used in the beverage industry to mimic the flavor of Hibiscus sabdariffa tea in commercially prepared drinks. In some comparative effectiveness trials it was difficult to compare effectiveness between treatments because the medication was not administered as directed by doctors 100), whereas other trials provided realistic comparators. The results from the study on dose response are difficult to interpret because the baseline values for total cholesterol differed substantially between groups 101).

Additionally, there were several problems specific to the cholesterol randomized clinical trials. Differences between groups were impossible to assess because none of the studies included effect sizes or statistical analyses of the between-group differences. Another problem with most of the cholesterol trials was short study duration with 4 trials lasting 15 days to 30 days and only one trial of a longer 90 day duration. In general, lipid profiles can take up to 2 months to reflect meaningful change in patients given statin medication or modifications to their diet and lifestyle 102). The hypertension trials selected patient populations with mild to moderate hypertension with only one study providing the additional condition of diabetes, whereas the patient populations in the cholesterol trials had an array of conditions, many of which did not include elevated cholesterol, making it difficult to assess the effectiveness of Hibiscus sabdariffa in treating hyperlipidemia.

There were also several problems with the preparation of Hibiscus sabdariffa. Many of the studies did not report the part of the plant that was used in the preparation. Kuriyan and colleagues 103) used the leaves in their extract without explanation, whereas the calyxes are most commonly used in Hibiscus sabdariffa preparations. In addition, the amount of Hibiscus sabdariffa used in preparations and the dose administered varied greatly with Mohagheghi and colleagues 104) choosing to use an extremely small amount of Hibiscus sabdariffa calyxes in the preparation per dose and many of the studies failing to include any measure of marker constituents. The absence of information related to product content and the method of preparation and the lack of uniformity of extracts made it difficult to compare findings between studies. In addition, the lack of information regarding ethnobotanical use made it difficult to determine the relationship between the studies and traditional therapeutic use.

Table 5. Cholesterol and Hibiscus sabdariffa randomized clinical trials and effects on total cholesterol, HDL-C, LDL-C, and triglycerides

Primary author, yearConditionSample sizeSubstancePlant partExtract modeDose# of doses per dayDays dose takenTC (SD)HDL-C (SD)LDL-C (SD)TG (SD)
0206 (39)44.3 (8.3)130.8 (29)153.5 (59)
Mohagheghi, 2011 105)Hyperten45 (42)HSCW.015/2a215212 (37)46 (7.2)133.2 (26)157.5 (58)
0202.6 (41.6)41.6 (10.3)124.1 (41.7)148.0 (61.3)
Gurrola-Diaz, 2010 106)None26 (26)HSCA100b130197.5 (37.0)45.8 (9.3)124.5 (35.5)113.8 (54.1)
0199.8 (40.5)32.0 (5.8)130.1 (34.8)172.3 (107.4)
Gurrola-Diaz, 2010 107)MeSy18 (18)HSCA100b130179.7 (21.2)44.5 (8.3)104.1 (20.4)137.6 (62.1)
0207.1 (32.5)42.0 (9.4)155.3 (13.9)159.9 (90.6)
Kuriyan, 2010 108)Hyperlip30 (28)HSLA500b290198.5 (33.2)42.6 (8.9)127.6 (24.1)143.3 (73.9)
0236.2 (58.1)48.2 (10.6)137.5 (53.4)246.1 (84.9)
Mozaffari-Khosravi, 2009 109)Diab30 (27)HSCW2/240c230218.6 (38.4)56.1 (11.3)128.5 (41.2)209.2 (57.2)
Lin, 2007 110)Hyperlip14 (N/A)HSFW500b30201.9 (27.2)
28194.6 (24.2)
60223.4 (36.8)
Lin, 2007 111)Hyperlip14 (N/A)HSFW500b28213.9 (37.0)
90207.5 (26.5)
Lin, 2007 112)Hyperlip14 (N/A)HSFW500b28212.6 (40.0)

Notes:

Condition: Hyperten=hypertension, MeSy=metabolic syndrome, Hyperlip=hyperlipidemia, Diab=diabetes; Sample size= beginning of study (end of study), N/A=not available; Substance: HS=Hibiscus sabdariffa; Plant part used in extract=F=flower, C=calyx, L=leaf; Extract mode: W=water, A=alcohol;

Dose: a=g substance/glass of extraction substance,

bmg of HS extract,
cg of substance/mL of extraction substance; TC=total cholesterol, HDL-C= high-density lipoprotein cholesterol, LDL-C=low-density lipoprotein cholesterol, TG=triglycerides, SD=standard deviation; Results: NS=not significant, Reduced=Red, Increased=Inc
[Source 113)]

Hibiscus tea side effects

Hibiscus sabdariffa extracts have a low degree of toxicity with a LD50 (Lethal Dose 50% is the amount of the substance required (usually per body weight) to kill 50% of the test population) ranging from 2,000 to over 5,000 mg/kg/day 114). There is no evidence of hepatic or renal toxicity as the result of Hibiscus sabdariffa extract consumption, except for possible adverse hepatic effects at high doses 115).

Summary

Hibiscus sabdariffa extracts are generally considered to have a low degree of toxicity. Studies demonstrate that Hibiscus sabdariffa consumption does not adversely effect liver and kidney function at lower doses, but may be hepatotoxic at extremely high doses. In addition, electrolyte levels generally are not effected by ingesting Hibiscus sabdariffa extracts despite its diuretic effects.

The daily consumption of Hibiscus sabdariffa calyx extracts significantly lowered systolic blood pressure and diastolic blood pressure in adults with prehypertension to moderate essential hypertension and type 2 diabetes 116). In addition, Hibiscus sabdariffa tea was as effective at lowering blood pressure as Captropril, but less effective than Lisinopril. McKay and colleagues 117) provide a notable exception with their high quality placebo-controlled trial. As the findings related to the effects of Hibiscus sabdariffa on blood pressure from lower quality studies are consistent with those of this high quality study, the totality of evidence suggests that Hibiscus sabdariffa consumption may have a public health benefit due to its anti-hypertensive effects. However, in a more recent 2015 systematic review on the effectiveness of Hibiscus sabdariffa in the treatment of hypertension 118) found no reliable evidence to recommend Hibiscus sabdariffa as a treatment for primary hypertension in adults. The four randomized controlled studies identified in this review 119) do not provide reliable evidence to support recommending Hibiscus sabdariffa for the treatment of primary hypertension in adults. Based on available conflicting evidence, more studies are needed before Hibiscus sabdariffa can reliably be recommended for the treatment of primary hypertension in adults.

Over half of the randomized clinical trials showed that daily consumption of Hibiscus sabdariffa tea or extracts had a favorable influence on lipid profiles including reduced total cholesterol, LDL “bad” cholesterol, triglycerides as well as increased HDL “good” cholesterol. Regrettably many of the randomized clinical trials were of low quality and did a poor job characterizing the Hibiscus sabdariffa extracts and utilized a form that is not widely consumed making it difficult to determine the amount of public health benefit related to Hibiscus sabdariffa tea consumption. In a 2013 systematic review and meta analysis on the effects of Hibiscus sabdariffa on blood cholesterol, Aziz et al. 120) found based available evidence from randomized clinical trials does not support the efficacy of Hibiscus sabdariffa L. in lowering serum lipids. Overall, Hibiscus sabdariffa L. did not produce any significant effect on any of the outcomes examined, when compared with placebo, black tea or diet. Further rigorously designed trials with larger sample sizes are warranted to confirm the effects of Hibiscus sabdariffa on serum lipids.

Anthocyanins found in abundance in Hibiscus sabdariffa calyxes are generally considered the phytochemicals responsible for the antihypertensive and hypocholesterolemic effects, however evidence has also been provided for the role of polyphenols and hibiscus acid. A number of potential mechanisms have been proposed to explain the hypotensive and anticholesterol effects, but the most common explanation is the antioxidant effects of the anthocyanins inhibit LDL “bad” cholesterol oxidation which impedes atherosclerosis, an important cardiovascular risk factor. Research on active compounds in Hibiscus sabdariffa and the mechanisms of action are still fairly nascent making it difficult to justify carrying out randomized clinical trials using anything other than the whole plant parts used in general practice.

This body of evidence interpreted together suggests that Hibiscus sabdariffa may have potential to reduce risk factors associated with cardiovascular disease (e.g. hypertension) and merits further study.

References   [ + ]

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