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Western herbalism

HibiscusHibiscus sabdariffa

Roselle calyx, a tart red tea. We found no human gut trial; the trials that exist are for blood pressure (5 trials pooled: 7.58 mmHg lower systolic).

Botanical name
Hibiscus sabdariffa
Part used
calyx (the fleshy red sepals that surround the fruit)
Also called
Roselle, Red sorrel, Karkade (Arabic), Jamaica (Mexico), Sour tea
Used in
Western herbalism
Taken for
Constipation
Sold as
tea, powder, capsules, extract

Hibiscus, the plant and the part used

Hibiscus sabdariffa, called roselle, red sorrel or karkade, is a tropical shrub in the mallow family. The part used is not the showy petal but the calyx, the fleshy red cup of sepals that swells around the seed pod. Ali and colleagues describe the calyces as the base of cold and hot drinks in many parts of the world, and they are a source of vitamin C.

The dried calyces are steeped whole or cut into a deep red, sour tea that is served hot or cold. Supplement makers also sell calyx powder and standardized extracts in capsules. Roselle is a different species from the common ornamental shrub Hibiscus rosa-sinensis.

In supplement catalogs it is usually included for its tea-like flavor and its polyphenols rather than as a stand-alone gut herb, and the evidence summarized below reflects that: the published trials are almost all about blood pressure and blood lipids, not digestion.

Traditional uses, in their own terms

Western herbalism

Ali and colleagues report that in folk medicine the calyx extracts are used for high blood pressure, liver complaints and fever, and the drink is a staple in Sudan, Egypt and elsewhere. German herbal reference works, as summarized in the Altmeyers encyclopedia, list the flowers as a mild laxative and a tea for colds and catarrh; the German herbal expert panel (the E monographs) issued a negative monograph for it because no efficacy studies existed. We found no European or WHO monograph that approves it for a gut complaint.

Compounds, and what the laboratory says about them

Da-Costa-Rocha and colleagues list the main constituents as anthocyanins (delphinidin-3-sambubioside and cyanidin-3-sambubioside, which give the red color), phenolic acids led by protocatechuic acid, and organic acids including hydroxycitric acid and hibiscus acid. In laboratory and animal work, calyx extracts show antioxidant, antibacterial, diuretic, blood-pressure-lowering and cholesterol-lowering effects. Ali and colleagues add that the effect of calyx extracts on isolated smooth muscle is variable but mostly lowers its tone. These are laboratory and animal findings and have not been tied to a gut outcome in people.

Trials in people, with the numbers

We searched PubMed for randomized trials of hibiscus for constipation, bowel, stomach or dyspepsia outcomes and found none. The traditional use as a mild laxative has therefore not been tested in a controlled human trial that we could find, and the laboratory work on smooth muscle (mostly relaxing it) does not point clearly to a laxative effect either. The antibacterial results, including work on Helicobacter pylori, are laboratory studies and have no human trial behind them.

What does exist is a sizable cardiometabolic literature. Serban and colleagues pooled 5 randomized trials (7 treatment arms, 390 people) and found systolic blood pressure 7.58 mmHg lower and diastolic 3.53 mmHg lower than control. A later umbrella review and dose-response meta-analysis by Norouzzadeh and colleagues covered 26 randomized trials with 1,797 participants: hibiscus lowered systolic and diastolic pressure in a dose-dependent way, with no significant difference from antihypertensive drugs in the comparisons available, and also lowered total and LDL cholesterol and fasting glucose while raising HDL. They noted a small rise in aspartate aminotransferase that they judged clinically insignificant.

Da-Costa-Rocha and colleagues, reviewing the field, conclude that better-controlled trials using chemically characterized preparations are needed and that the safety and tolerability record is excellent. Mahmoud and colleagues studied healthy men given chloroquine with different Sudanese drinks and found the karkade drink cut chloroquine exposure sharply (area under the curve 2.16 mg.h/L versus 7.52 with water; the lemon and tamarind drinks lowered it too).

Nothing we found measures a gut symptom, stool frequency or the microbiome in people given hibiscus.

StudyDoseWhat it found
Umbrella review and dose-response meta-analysis, 26 randomized trials, 1,797 people PMID 39870328Varied; effect rose with doseLower systolic and diastolic pressure than placebo; lower total and LDL cholesterol; small rise in AST judged clinically insignificant
Meta-analysis of 5 randomized trials (7 arms), 390 people PMID 25875025Tea or extract, variedSystolic pressure 7.58 mmHg lower and diastolic 3.53 mmHg lower than control
Crossover study in healthy men, chloroquine 600 mg taken with water or Sudanese drinks PMID 8089046One drink with the single drug doseChloroquine exposure (AUC) 2.16 mg.h/L with the hibiscus drink versus 7.52 with water

The doses on record

We found no dose tested for a gut outcome. The blood pressure trials in the reviews above used teas and standardized extracts in varying amounts, and the umbrella review reports a dose-dependent effect without naming one standard dose. The traditional preparation is whole or cut dried calyces steeped in hot water, or soaked cold, and drunk as a tart tea; Ali and colleagues describe both hot and cold drinks. Capsule products carry their own per-capsule amounts, which differ from brand to brand.

None of this is a dose recommendation. It is what the literature used, set down so a label can be compared with it; a pharmacist or clinician decides what applies to you.

The safety record

Da-Costa-Rocha and colleagues describe an excellent safety and tolerability record, and Ali and colleagues report very low toxicity in animals (a median lethal dose above 5,000 mg/kg in rats), with a single report of testicular effects in rats given excessive doses for a long time. In the pooled human trials the only laboratory change noted was a small rise in aspartate aminotransferase that the authors called clinically insignificant.

Because trials show it lowers blood pressure by amounts comparable with some medicines, people who already run low blood pressure are a group the trial data flag for attention. We found no human data on pregnancy or breastfeeding in the sources we read, and no EU or WHO monograph addresses it. The calyx is acidic and tart.

Medicines it can interact with

Blood pressure medicines: hibiscus lowered pressure by roughly the amount some antihypertensive drugs did in the pooled trials, so stacking the two is a plausible additive effect, though we found no formal interaction study. Chloroquine: the Sudanese drink study above showed a large fall in drug exposure when taken together with karkade, and an equally large fall with lemon and tamarind drinks, so the drink as a whole, not hibiscus alone, may be responsible. Other drugs have not been studied the same way in the sources we read.

Where hibiscus turns up in the catalog

Hibiscus appears on the labels below, alone or inside a blend; each product page gives the printed amount, the evidence for that product and the review picture.

PiPi Tea Organic Hibiscus Tea Bags 4.3 out of 5 from 586 ratings from Amazon · $1.17 a day

Match it to your own case

The quiz weighs your symptoms and medicines against every product researched here, hibiscus products included, and shows its working.

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Common questions

Is hibiscus tea a laxative?

It is listed as a mild laxative in German herbal reference works, but we found no controlled trial testing it for constipation. The German E monographs panel issued a negative monograph for it for lack of efficacy studies, so the laxative use rests on tradition only.

What do the human trials of hibiscus actually measure?

Almost all measure blood pressure and blood lipids. One pooling of 5 trials found systolic pressure 7.58 mmHg lower than control, and a later review of 26 trials found lower blood pressure and cholesterol. None of that is a gut outcome.

Does hibiscus interact with medicines?

In a small study of healthy men, drinking karkade with chloroquine cut the drug’s exposure from 7.52 to 2.16 mg.h/L, though lemon and tamarind drinks did the same. Its blood pressure effect also makes stacking with blood pressure medicines plausible, but we found no formal study of that.

Is hibiscus the same as the hibiscus in garden hedges?

No. The tea comes from the calyx of Hibiscus sabdariffa, called roselle. The common ornamental shrub is a different species, Hibiscus rosa-sinensis.

Is hibiscus safe long term?

Reviews describe an excellent safety record, and the pooled trials noted only a small rise in one liver enzyme that the authors called clinically insignificant. Trials were mostly short, so long-term data are thinner than the short-term record.

Sources