Effect of Gymnema sylvestre Administration on Glycemic Control, Insulin Secretion, and Insulin Sensitivity in Patients with Impaired Glucose Tolerance

Gymnema sylvestre, a plant typical of India, has long been known for its hypoglycemic effects. The objective of this study was to evaluate the effect of G. sylvestre administration on glycemic control, insulin secretion, and insulin sensitivity in patients with impaired glucose tolerance (IGT). A randomized, double-blind, placebo-controlled clinical trial was conducted in 30 patients with IGT. Fifteen patients randomly received G. sylvestre in doses of 300 mg b.i.d. and the other 15 received placebo in the same way. Before and after the intervention, anthropometric and metabolic measurements were taken, including 2-h oral glucose tolerance test (2-h OGTT), fasting plasma glucose, glycated hemoglobin A1c (A1C), and the lipid profile panel. Areas under the curve of glucose and insulin were calculated, as well as the insulinogenic, Stumvoll, and Matsuda indices. Wilcoxon, Mann-Whitney U, and chi-square or Fisher's exact tests were performed, and a P-value <=.05 was considered statistically significant. There was a significant reduction in 2-h OGTT (9.1 +/- 1.2 vs. 7.8 +/- 1.7 mmol/L, P = .003), A1C (5.8 +/- 0.3% vs. 5.4 +/- 0.4%, P = .025), body weight, body mass index, and low-density lipoprotein cholesterol levels in the G. sylvestre group, with an increment in the Matsuda index (1.8 +/- 0.8 vs. 2.4 +/- 1.2, P = .008). At the end of the intervention, 46.7% of the patients obtained normal values in A1C. In conclusion, G. sylvestre administration in patients with IGT decreased 2-h OGTT and A1C, increasing insulin sensitivity. There were also improvements in anthropometric measures and the lipid profile.