Gymnema

Gymnema is meshashringi in Sanskrit, “ram’s horn”, and gurmar in Hindi, “sugar destroyer” ^{19Reference 19Tiwari et al. · 2014ReviewPhytochemical and pharmacological properties of Gymnema sylvestre: an important medicinal plant — reviewView study →}. The leaf is the part used for diabetes and related disorders, while the flowers and bark are given for conditions of phlegm ^{19Reference 19Tiwari et al. · 2014ReviewPhytochemical and pharmacological properties of Gymnema sylvestre: an important medicinal plant — reviewView study →}.

The classical text of Sushruta describes gurmar as a destroyer of madhumeha, glycosuria, and of other urinary disorders ^{19Reference 19Tiwari et al. · 2014ReviewPhytochemical and pharmacological properties of Gymnema sylvestre: an important medicinal plant — reviewView study →}. The leaf is taken fresh, as a dried powder or as a decoction.

Indian traditional medicine also records the plant for dyspepsia, constipation, jaundice, cough and fever. The root juice is used for snakebite ^{19Reference 19Tiwari et al. · 2014ReviewPhytochemical and pharmacological properties of Gymnema sylvestre: an important medicinal plant — reviewView study →}.

In southern China the plant is chi geng teng. All parts are used for rheumatism, inflamed blood vessels, haemorrhoids and snakebite ^{26Reference 26Li et al. · 1995Asclepiadaceae: Gymnema sylvestre — flora treatmentView study →}.

Western practice uses the leaf for the same metabolic indications as Ayurveda. It is given as a 1:2 liquid extract or a standardised leaf extract, usually within formulas alongside other herbs for blood sugar, and it is chewed or held in the mouth to blunt sweet cravings.

A 2021 meta-analysis of 10 studies (419 participants) found that gymnema lowered fasting and after-meal blood sugar and HbA1c in type 2 diabetes, compared with baseline values ^{1Reference 1Devangan et al. · 2021Meta-analysisThe effect of Gymnema sylvestre supplementation on glycemic control in type 2 diabetes patients: A systematic review and meta-analysisView study →}. A 2023 meta-analysis of six randomised trials found lower fasting blood sugar, and noted marked heterogeneity and low study quality ^{2Reference 2Zamani et al. · 2023Meta-analysisThe effects of Gymnema sylvestre supplementation on lipid profile, glycemic control, blood pressure, and anthropometric indices in adults: A systematic review and meta-analysisView study →}.

In the first human study, 22 people with type 2 diabetes took 400 mg a day of the leaf extract GS4 with their usual drugs for 18–20 months. Blood sugar, HbA1c and glycated plasma proteins fell, drug doses could be reduced, and five of the 22 stopped their conventional drug ^{3Reference 3Baskaran et al. · 1990Clinical trialAntidiabetic effect of a leaf extract from Gymnema sylvestre in non-insulin-dependent diabetes mellitus patients — clinical trialView study →}.

In 27 people with type 1 diabetes, the same 400 mg daily dose lowered insulin requirements, fasting blood sugar and HbA1c, although HbA1c stayed above that of healthy controls ^{4Reference 4Shanmugasundaram et al. · 1990Clinical trialUse of Gymnema sylvestre leaf extract in the control of blood glucose in insulin-dependent diabetes mellitus — clinical trialView study →}.

In a later open-label study, people with type 2 diabetes chose whether to join the treatment group. Three months of 500 mg a day lowered fasting and after-meal blood sugar and HbA1c, and reduced hunger and fatigue ^{7Reference 7Kumar et al. · 2010Clinical trialAn open label study on the supplementation of Gymnema sylvestre in type 2 diabetics — controlled clinical trialView study →}.

Gap: there is no large, long, double-blind trial with HbA1c as the main outcome, and both meta-analyses rate the underlying studies as low quality.

A 2023 meta-analysis of six randomised trials found lower triglycerides, total cholesterol and LDL cholesterol, and lower diastolic blood pressure, with gymnema supplementation ^{2Reference 2Zamani et al. · 2023Meta-analysisThe effects of Gymnema sylvestre supplementation on lipid profile, glycemic control, blood pressure, and anthropometric indices in adults: A systematic review and meta-analysisView study →}.

A randomised trial in 75 people with type 2 diabetes tested gymnema combined with inositols, α-lactalbumin and zinc. Total and LDL cholesterol fell after three months, while blood sugar did not differ from placebo ^{20Reference 20Nani et al. · 2023RCTCombined inositols, α-lactalbumin, Gymnema sylvestre and zinc improve the lipid metabolic profile of patients with type 2 diabetes mellitus: a randomised clinical trialView study →}.

Reviews of the animal work attribute the effect to gymnemic acids reducing the absorption of glucose and fat and the build-up of triglycerides in liver and muscle ^{8,22Reference 8Pothuraju et al. · 2014Systematic reviewA systematic review of Gymnema sylvestre in obesity and diabetes managementView study →Reference 22Di Fabio et al. · 2014ReviewTriterpenoids from Gymnema sylvestre and their pharmacological activities — reviewView study →}.

Gap: the strongest trial evidence comes from combination products, so the effect cannot be attributed to gymnema alone.

Chewing the leaf or holding a gymnemic-acid solution in the mouth temporarily blocks the taste of sweetness, the property behind the name gurmar. A 2023 systematic review of 33 human studies found that most research looks at this immediate effect of oral gymnemic acids, and that results on whether it changes appetite or food intake are inconsistent ^{10Reference 10Rayo-Morales et al. · 2023Systematic reviewSuppression of sweet taste-related responses by plant-derived bioactive compounds and eatingView study →}.

The second sweet-blocking constituent, the 35-amino-acid peptide gurmarin, suppresses sweet taste in rodents ^{11Reference 11Sigoillot et al. · 2018The crystal structure of gurmarin, a sweet taste-suppressing protein: identification of the amino acid residues essential for inhibitionView study →}. It has no effect, or only a very weak one, in humans. A computer model predicts that a related peptide, Gur-2, may bind the human sweet receptor T1R2/T1R3, but this has not been tested ^{12Reference 12Maaroufi et al. · 2024Novel gurmarin-like peptides from Gymnema sylvestre and their interactions with the sweet taste receptor T1R2/T1R3 — in silicoView study →}.

Gap: there is no consistent evidence that blocking sweet taste leads to lower sugar intake or weight change over time.

In a randomised, double-blind, placebo-controlled trial, 24 people with metabolic syndrome took 300 mg twice a day or placebo for 12 weeks. On gymnema, body weight, BMI and VLDL cholesterol fell, but the components of metabolic syndrome, insulin secretion and insulin sensitivity did not change ^{5Reference 5Zuñiga et al. · 2017RCTEffect of Gymnema sylvestre administration on metabolic syndrome, insulin sensitivity, and insulin secretion — randomised, double-blind, placebo-controlled trialView study →}.

In a three-month comparison in 50 adults with obesity, gymnema lowered fasting blood sugar and the expression of resistin, an adipokine linked to insulin resistance. Berberine, the comparison treatment, reduced body weight and blood pressure ^{21Reference 21Bandala et al. · 2024RCTComparative effects of Gymnema sylvestre and berberine on adipokines, body composition, and metabolic parameters in obesity — randomised controlled trialView study →}.

A systematic review describes gymnemic acid as reducing body weight and glucose absorption, mostly on the basis of animal studies ^{8Reference 8Pothuraju et al. · 2014Systematic reviewA systematic review of Gymnema sylvestre in obesity and diabetes managementView study →}.

Gap: trials are small and short, and there are no long-term weight data.

In a small group of people with type 2 diabetes, a high-molecular-weight extract (OSA) at 1 g a day for 60 days raised blood insulin and C-peptide and lowered fasting and after-meal blood sugar. The same extract stimulated insulin release from isolated human islets ^{6Reference 6Al-Romaiyan et al. · 2010Clinical trialA novel Gymnema sylvestre extract stimulates insulin secretion from human islets in vivo and in vitro — clinical trialView study →}.

The GS4 trials proposed that the extract regenerates or revives the remaining β-cells, based on rising insulin levels ^{3,4Reference 3Baskaran et al. · 1990Clinical trialAntidiabetic effect of a leaf extract from Gymnema sylvestre in non-insulin-dependent diabetes mellitus patients — clinical trialView study →Reference 4Shanmugasundaram et al. · 1990Clinical trialUse of Gymnema sylvestre leaf extract in the control of blood glucose in insulin-dependent diabetes mellitus — clinical trialView study →}.

In rat islets and β-cell lines, the extract GS4 released insulin by making the cells more permeable rather than through normal secretion, and the same concentrations let the cells take up trypan blue dye, a sign of membrane damage ^{9Reference 9Persaud et al. · 1999In vitroGymnema sylvestre stimulates insulin release in vitro by increased membrane permeability — in vitro/rat studyView study →}.

Gap: part of the effect may come from membrane damage, and β-cell regeneration in humans is inferred from insulin levels, not shown directly.

An ethanol leaf extract showed antioxidant activity in laboratory assays. In diabetic rats it brought blood sugar down to normal, lowered lipid peroxidation in serum, liver and kidney, and returned liver glutathione peroxidase activity to normal ^{13Reference 13Kang et al. · 2012AnimalHypoglycemic activity of Gymnema sylvestre extracts on oxidative stress and antioxidant status in diabetic rats — animal modelView study →}.

LC/MS analysis detected gymnemagenin and gymnemic acids in the extract ^{13Reference 13Kang et al. · 2012AnimalHypoglycemic activity of Gymnema sylvestre extracts on oxidative stress and antioxidant status in diabetic rats — animal modelView study →}.

Gap: the effects are in animals and laboratory assays, and in the rats they cannot be separated from the fall in blood sugar.

A hydroalcoholic leaf extract reduced lung injury caused by bacterial lipopolysaccharide in a rat model of acute respiratory distress syndrome. It lowered inflammatory cytokines and reactive oxygen species through the NF-κB/MAPK and NRF2 pathways, and a fraction rich in gymnemic acids was more active at lower concentrations ^{14Reference 14Jangam et al. · 2023AnimalAnti-inflammatory and antioxidant activities of Gymnema sylvestre extract rescue acute respiratory distress syndrome in rats via modulating the NF-κB/MAPK pathway — animal modelView study →}.

In mice, a purified gymnemic acid fraction had anti-stress and anti-allergic activity against milk-induced eosinophilia, and leaf extracts protected against aspirin-induced stomach ulcers ^{15Reference 15Arun et al. · 2014AnimalIn vivo anti-ulcer, anti-stress, anti-allergic, and functional properties of gymnemic acid isolated from Gymnema sylvestre RView study →}.

Gap: single animal models at doses not related to human use.

A glycolic extract of gymnema stem and leaf, tested with three other plant extracts, reduced mixed biofilms of Candida albicans with Streptococcus mutans, Staphylococcus aureus, Enterococcus faecalis or Pseudomonas aeruginosa after 24 hours. The authors suggested the extracts as possible root-canal irrigants ^{17Reference 17Domingues et al. · 2023In vitroAntimicrobial action of four herbal plants over mixed-species biofilms of Candida albicans with four different microorganisms — in vitroView study →}.

Gap: one laboratory study, with no clinical or animal data.

An ethanolic leaf extract killed human A375 melanoma cells in a dose-dependent way through reactive oxygen species and a mitochondrial caspase pathway, with less effect on normal liver cells ^{16Reference 16Chakraborty et al. · 2013In vitroAntihyperglycemic drug Gymnema sylvestre also shows anticancer potentials in human melanoma A375 cells via reactive oxygen species generation and mitochondria-dependent caspase pathway — in vitroView study →}.

Gap: a single cell-line study, with no animal or human data.

Diabetes medicines. Gymnema lowers blood sugar and may increase insulin secretion. In the GS4 trials, doses of oral diabetes drugs could be reduced and insulin requirements fell ^{3,4Reference 3Baskaran et al. · 1990Clinical trialAntidiabetic effect of a leaf extract from Gymnema sylvestre in non-insulin-dependent diabetes mellitus patients — clinical trialView study →Reference 4Shanmugasundaram et al. · 1990Clinical trialUse of Gymnema sylvestre leaf extract in the control of blood glucose in insulin-dependent diabetes mellitus — clinical trialView study →}. Anyone taking insulin or other glucose-lowering drugs should monitor blood sugar closely when starting it.

Liver injury. A 2022 report described two patients who developed acute hepatitis followed by bone-marrow failure after taking Ayurvedic and homeopathic remedies, including gymnema; both died ^{18Reference 18Philips et al. · 2022Case reportToxic hepatitis-associated aplastic anaemia after dual homeopathic remedies and Gymnema sylvestre use — case reportView study →}. In a laboratory study of slimming products taken by a patient with liver injury, gymnema extract strongly reduced the survival of human liver cells ^{25Reference 25Adachi et al. · 2024In vitroExploring acute liver damage: slimming health foods and CYP3A4 induction — in vitro / animalView study →}.

Drug-metabolising enzymes. There are no human interaction studies. In rats given an ethanolic leaf extract for seven days, blood levels of phenacetin, a CYP1A2 test drug, rose 1.3–1.4-fold ^{23Reference 23Vaghela et al. · 2017AnimalIn vivo pharmacokinetic interaction by ethanolic extract of Gymnema sylvestre with CYP2C9 (tolbutamide), CYP3A4 (amlodipine) and CYP1A2 (phenacetin) in rats — animalView study →}.

In the same rats, blood levels of the diabetes drug tolbutamide, which is cleared by CYP2C9, fell by more than half. Amlodipine, a CYP3A4 drug, was not affected ^{23Reference 23Vaghela et al. · 2017AnimalIn vivo pharmacokinetic interaction by ethanolic extract of Gymnema sylvestre with CYP2C9 (tolbutamide), CYP3A4 (amlodipine) and CYP1A2 (phenacetin) in rats — animalView study →}.

An aqueous leaf extract made to the Ayurvedic Pharmacopoeia of India did not inhibit CYP3A4 in rat liver microsomes ^{24Reference 24Borse et al. · 2015In vitroEffects of Ayurvedic Rasayana botanicals on CYP3A4 isoenzyme system — in vitro (rat liver microsomes)View study →}. In the study of slimming products, the CYP3A4 induction came from Coleus forskohlii extract and another supplement, not from gymnema ^{25Reference 25Adachi et al. · 2024In vitroExploring acute liver damage: slimming health foods and CYP3A4 induction — in vitro / animalView study →}.

Side effects. In a three-month trial, gastrointestinal symptoms were the commonest side effect and eased during the first month ^{21Reference 21Bandala et al. · 2024RCTComparative effects of Gymnema sylvestre and berberine on adipokines, body composition, and metabolic parameters in obesity — randomised controlled trialView study →}.