Gymnema and diabetes - Phytotherapy Review & Commentary - Brief Article

Townsend Letter for Doctors and Patients,  June, 2002  by Kerry Bone

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Gymnema sylvestre is a liana or climbing plant with stems up to 8 m in length. It grows in open woods and bushland at an altitude of 100-1000 m in India, China, Indonesia, Japan, Malaysia, Sri Lanka, Vietnam and South Africa: Both the leaf and root are used in Ayurvedic medicine. Because of its property of abolishing the taste of sugar it was given the Hindi names of Gurmar and Madhunashini meaning 'sugar destroying.' The sweet taste suppressant property of Gymnema was revealed to a British officer by the inhabitants of a northern Indian village in the mid-19th century. The herb is traditionally used for the treatment of diabetes and Gymnema extracts are sold in Japan for the control of obesity.

A clinical trial recently conducted in the US provides further support for the use of this herb in the management of insulindependent (Type I) and non-insulin-dependent (Type II) diabetes. Of 65 patients tested over the 90-day trial, Gymnema tablets reduced mean fasting glucose levels by 11%. Average post-meal glucose levels showed a decline of 13% and HbA1c's dropped 6.8%. In a subset of patients with the poorest control, results were more substantial. Pre-meal readings averaged an 18% decline, with post-meal levels reduced by 28%. Corresponding HbA1c's declined 10 percent. Improved glucose control with Gymnema enabled 16% of the participants to decrease their prescription medication usage. (1)

The tablets used in the trial contained 400 mg of Gymnema extract (equivalent to around 4 g of leaf) standardized to 25% gymnemic acids. The dose used was two tablets per day.

Commentary: Previous clinical trials have recorded benefits for the use of Gymnema in diabetic patients. A controlled study on insulin-dependent diabetics found that a water-soluble Gymnema extract (400 mg/day) reduced insulin requirements (by about 50%). Over the duration of treatment Gymnema lowered fasting mean blood glucose (by about 35%), glycosylated hemoglobin and glycosylated plasma protein levels from baseline values. Cholesterol was significantly reduced and brought to near normal levels. Triglycerides, free fatty acids and serum amylase were also lowered. The treatment period ranged from 6-30 months. The significant decrease in glycosylated hemoglobin occurred after 6-8 months of Gymnema treatment but remained significantly higher than normal values. None of these reductions was observed in control patients on insulin therapy alone who were studied over a period of 10-12 months. The authors suggested that Gymnema enhanced endogenous insulin production, possibly by pancreatic regeneration, as level s of C-peptide, a by-product of the conversion of proinsulin to insulin, were apparently raised (in comparison to both the insulin alone group and normal subjects). (2)

A second study by the same research group found that the same Gymnema preparation (400 mg/day) produced similar results for non-insulin-dependent diabetics. Fasting blood glucose, glycosylated hemoglobin and glycosylated plasma protein were significantly reduced compared to baseline values (p<0.001) after 18-20 months of treatment. None of these reductions was observed in patients receiving conventional therapy alone who were studied over a period of 10-12 months. By the end of the treatment period cholesterol, triglycerides, phospholipids and free fatty acid levels were also significantly reduced compared to baseline values in those receiving Gymnema (p<0.001). Control patients receiving only conventional therapy achieved reductions in cholesterol, triglycerides and free fatty acids (p<0.05-p<0.001). Fasting and post-prandial serum insulin levels were significantly increased in the Gymnema group compared to those taking only conventional drugs (p<0.01). Twenty-one of the 22 patients were able to reduce thei r intake of hypoglycemic drugs; 5 of these discontinued hypoglycemic drugs entirely and maintained their blood glucose homeostasis with Gymnema extract alone. The authors' suggestion of beta cell regeneration or repair facilitated by Gymnema was supported by the higher insulin levels in the serum of patients after Gymnema supplementation. Gymnema administration to healthy volunteers did not produce any acute reduction in fasting blood glucose level. (3)

The current trial adds further weight to the value of prescribing Gymnema for diabetics. However all three trials share the same basic methodological flaw: the lack of a placebo control group. Since non-insulin-dependent diabetes is a progressive disorder, it generally shows a negative placebo effect in clinical trials. However, the credibility of Gymnema as a viable adjunct in the management of diabetes must be supported by well-designed placebo and/or drug-controlled trial designs.

(1.) Joffe DJ, Freed SH. Effect of Extended Release Gymnema Sylvestre Leaf Extract Alone or In Combination With Oral Hypoglycemics or Insulin Regimens for Type 1 and Type 2 Diabetes. The Newsletter for Professionals in Diabetes Care. Oct 31, 2001; Issue 76.