RELEVANT SELECTED CLINICAL TRIALS
Two small open-label trials have yielded promising results.
- 22 patients with type 2 DM were given either 200 mg of an ethanolic extract daily or their usual treatment for 18 to 20 months. Significant improvements in FBG and HbA1c levels (p<0.001 for both) were noted in the test group.
- The other trial was uncontrolled, but reported that 3 months of treatment with 800 mg daily of a similar extract reduced FBG levels by 11% and HbA1c levels by 0.6% in a mixed population of 65 patients with type 1 and type 2 diabetes.
No adverse effects were reported in either trial. Preliminary evidence of any benefit is probably insufficient to support the widespread use of GS for diabetes management at this time. The significant improvements in HbA1c levels definitely warrant further study as well as judicious use in selected patients.
Other two studies can be considered; however they do not report important design details, such as blinding or randomization (as we can often see in trials about these classes of substances).
- One study was conducted in type 1 diabetic patients on insulin, 27 of whom took 200 mg gymnema capsules after breakfast and supper and 37 of whom took insulin only for a period of 6–30 months. After 6–8 months, mean HbA1c decreased in the gymnema group from a baseline of 12.8 to 9.5% (p<0.001). After 16–18 months, 22 patients remaining on gymnema had a mean HbA1c of 9% (p values not given). At the end of 26–30 months, six patients remaining on gymnema had a mean HbA1c of 8.2% (p values not given). Mean fasting blood glucose (FBG) also decreased from a baseline of 232 to 177 mg/dl after 6–8 months, 150 mg/dl after 16–18 months and 152 mg/dl after 20–24 months (p values not given). The mean insulin dose decreased from a baseline of 60 to 45 units/day after 6–8 months and to 30 units/day at 26–30 months (p values not given). Patients on placebo had no significant changes from baseline.
Use of Gymnema sylvestre leaf extract in the control of blood glucose in insulin-dependent diabetes mellitus, 1990
- Another study was conducted in patients with type 2 diabetes on sulfonylureas; 22 took 400 mg/day of gymnema capsules in addition to sulfonylurea treatment and 25 took a placebo and sulfonylureas for a period of 18–20 months. Mean HbA1c decreased from a baseline of 11.9 to 8.48% (p<0.001). Mean FBG decreased from 174 to 124 mg/dl after 18–20 months (p<0.001). Five patients were able to discontinue sulfonylureas. In this study, lipids also decreased significantly. Patients on placebo had no significant changes in HbA1c, FBG, or lipids.
Antidiabetic effect of a leaf extract from Gymnema sylvestre in non-insulin-dependent diabetes mellitus patients, 1990
SIDE EFFECTS & TOXICITY
No side effects have been reported secondary to gymnema use, at least on a large scale (see the link below), even if hypoglycemia is the first potential side effect. Anyway, because other uses for gymnema leaf extract are based on its ability to act as a laxative and diuretic suppressant, these phenomena would be considered adverse reactions when Gymnema s. is used for its glucose lowering effect in diabetes. Moreover hypersensitivity can be a possible reason for problems.
Safety in pregnancy has not been established (caution).