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Herbal extract

Gymnema sylvestre

DWeak evidence

At a glance

Sweet-taste block
30–60 minutesGymnemic acids bind sweet receptors on the tongue. Only works if it touches the tongue — a swallowed capsule does not.
Sweets eaten after a lozenge
44% lessIn a 67-person placebo-controlled experiment, total candy intake fell by 44%. A short-term laboratory result.
Blood sugar trials
10 studies, 419 peopleA 2021 meta-analysis reported falls in glucose and HbA1c against baseline, but with extreme heterogeneity.
Typical capsule dose
200–800 mg a dayOf extract, usually standardised to about 25% gymnemic acids. Trial doses vary widely.
Two real risks
Low blood sugar, liverIt can add to diabetes medicines, and there are case reports of drug-induced hepatitis.

What is Gymnema sylvestre?

Gymnema sylvestre is a woody climbing plant native to the forests of India, Africa and Australia. Its leaves have been used in Ayurvedic medicine for centuries for what would now be called diabetes. The active compounds are a family of saponins called gymnemic acids. If you chew a gymnema leaf and then eat a spoonful of sugar, the sugar tastes like sand. That unusual effect is where the Hindi name gurmar, "sugar destroyer", comes from. Supplements come as capsules of dried leaf or extract, usually standardised to about 25 per cent gymnemic acids, and as lozenges, mints and teas designed to act on the tongue.

How it works

Gymnema has two separate proposed actions, and it matters which one a product relies on. The first is on the tongue. Gymnemic acids have a structure similar to glucose and bind to the sweet taste receptors, temporarily blocking them for roughly 30 to 60 minutes without affecting salty, sour, bitter or savoury tastes. This is well demonstrated in people, and it only happens if the gymnema touches your tongue. The second action, claimed for capsules, is on blood sugar. Laboratory and animal studies suggest gymnemic acids may slow sugar absorption from the gut and may support insulin release from the pancreas. The human evidence for this second action is far weaker than for the first.

What the research actually shows

Evidence strength varies by what is being claimed, so each use is graded separately against the published criteria rather than averaged into one reassuring letter.

Blocking sweet taste and reducing sugar cravings

BModerate evidence

This is the best-supported use, and it depends on the format. In a 2017 double-blind experiment published in the Journal of Psychopharmacology, 67 adults sucked either a gymnemic acid lozenge or a placebo after tasting their favourite sweets. The gymnema group was 31 per cent less likely to take the first offered serving, and total sweet intake fell by 44 per cent. Other studies of gymnema mints have found similar drops in desire and intake. The receptor mechanism is clearly established, which strengthens the case. B rather than A because the studies are short, mostly single sessions, and nobody has shown that the effect changes long-term sugar intake or weight. It also only works as a lozenge, mint or tea that touches the tongue, and taste returns within about an hour.

Sources: Stice E, Yokum S, Gau JM (2017)

Lowering blood sugar in type 2 diabetes

CLimited evidence

A 2021 meta-analysis in Phytotherapy Research pooled 10 studies with 419 participants. It reported reductions in fasting glucose, post-meal glucose and HbA1c. Before taking that at face value, look at how it was done: many comparisons were against the participants’ own starting values rather than a placebo group, and heterogeneity between studies was extreme, at 90 to 99 per cent. That means the trials disagreed so much that a single pooled number is hard to interpret. Several trials were small, unblinded or used gymnema alongside other herbs. There is a signal worth testing properly. There is not enough to treat gymnema as a diabetes therapy, and it must never replace prescribed medication.

Sources: The effect of Gymnema sylvestre supplementation on glycemic control in type 2 diabetes patients: a systematic review and meta-analysis

Weight loss

DWeak evidence

Gymnema is often added to fat burners and "carb blocker" products on the strength of the two actions above. There is no good trial evidence that it causes weight loss. A capsule cannot block sweet taste because it is swallowed, and the effect on sugar absorption in people is unproven. At best, a lozenge might help someone skip a dessert.

Effective dosage

Trials of gymnema for blood sugar have used widely varying doses, commonly 200 to 800 mg a day of extract standardised to about 25 per cent gymnemic acids, split across meals, and some older studies used more. For the sweet-taste effect the dose matters less than the format: a lozenge, mint or strong tea held in the mouth for a minute before eating something sweet. The effect lasts about 30 to 60 minutes.

Where products diverge from the research. The biggest gap is the format. Many products are capsules marketed for "sugar cravings", but a swallowed capsule never touches your taste buds and cannot deliver the one effect gymnema has reliably shown. The second gap is standardisation. A label listing gymnema leaf powder without a gymnemic acid percentage cannot be compared with trials that used standardised extracts. Third, in multi-ingredient fat burners gymnema is often a small part of a proprietary blend at an undisclosed dose.

Safety, side effects and interactions

The most important risk is low blood sugar in people who take diabetes medicines. If gymnema lowers glucose even modestly, it adds to the effect of insulin, sulfonylureas and other glucose-lowering drugs, and the combination could cause hypoglycaemia. Anyone with diabetes should discuss it with their prescriber before starting, and monitor glucose closely if they do. There are also published case reports of drug-induced liver injury, including a 60-year-old woman who developed acute hepatitis within one to two weeks of starting a gymnema tea; she recovered after stopping it and receiving treatment. Liver injury appears to be rare, but anyone who develops fatigue, dark urine, pale stools or yellowing skin while taking gymnema should stop and see a doctor. Stomach upset is the commonest minor side effect. It should be stopped before surgery because of the blood sugar effect, and there is not enough safety data for pregnancy or breastfeeding.

None of this is medical advice. See the medical disclaimer for what that means before you act on anything here.

Common questions

Does gymnema stop sugar cravings?

As a lozenge, mint or tea that touches your tongue, it temporarily blocks sweet taste for 30 to 60 minutes. In one controlled experiment that cut sweet intake by 44 per cent in a single session. A swallowed capsule does not touch your taste buds, so it cannot have this effect.

Does gymnema lower blood sugar?

Possibly, modestly. A 2021 meta-analysis of 10 small studies reported reductions in glucose and HbA1c, but many comparisons were against starting values rather than placebo, and the studies disagreed hugely. It is not a substitute for diabetes treatment.

Can I take gymnema with metformin or insulin?

Only after talking to your prescriber. If gymnema lowers blood sugar, it adds to your medicines, which could cause hypoglycaemia. If you are given the go-ahead, monitor your glucose more closely than usual when you start.

Will gymnema help me lose weight?

There is no good evidence that it does. Its reliable effect is blocking sweet taste for up to an hour, which might help you skip a dessert. That is not the same as a weight-loss effect.

Is gymnema safe for the liver?

Liver injury appears rare, but there are published cases of drug-induced hepatitis. Stop taking it and see a doctor if you develop tiredness, dark urine, pale stools or yellowing of the skin or eyes.

How long does the sweet-blocking effect last?

Usually 30 to 60 minutes. It affects only sweetness; salty, sour, bitter and savoury tastes are unchanged.

Related ingredients

Capsicum annuum (capsaicin) Glucomannan Psyllium husk

Compiled by SNL Team