SWEET TASTE SUPPRESSION AND WEIGHT LOSS
A controlled trial of normal volunteers found that an aqueous gymnema extract with concentrated gymnemicacid reduced sweetness perception by 50%, resulting in reduced caloric consumption 1.5 hours after the sweetness-numbing effect stopped. This result supports the findings of animal studies. In a 6-week randomised, double-blind, placebo-controlled study, a multi-herbal formula that included gymnema was found to significantly reduce body weight and fat loss in obese adults after 6 weeks; however, the role of gymnema in achieving these results is unknown.
DIABETES TYPE 1 AND TYPE 2
Orally, gymnema leaf is used to treat both type 1 and type 2 diabetes and hyperglycaemia. There are two clinical trials that suggest that gymnema may be useful in reducing blood glucose levels in both type 1 and type 2 diabetes. In one study the ability of the GS4 extract (400 mg/day) to supplement the use of conventional oral hypoglycaemic agents (glibenclamide or tolbutamide) was studied in 22 patients with type 2 diabetes over 18-20 months. Treatment resulted in a significant reduction in fasting blood glucose (174 ± 7 vs 124 ± 5 mg/dL), HbA1c (11.91 ± 0.3 vs 8.48 ± 0.13%) and glycosylated plasma protein levels (3.74 ± 0.07 vs 2.46 ± 0.05 µg hexose/mg protein) and raised insulin levels, whereas no changes were observed in the control group. This allowed for a decrease in conventional drug dosage and in five cases, blood glucose homeostasis was maintained with GS4 alone, suggesting that beta-cell function may have been restored. In a second study, 27 type 2 diabetes patients were treated with 400 mg of an aqueous extract of gymnema in addition to insulin. Insulin requirements were reduced, as were fasting blood sugar levels, HbA1c, glycosylated plasma protein levels and serum lipids.
A small, double-blind, randomised, placebo-controlled trial of a multi-herbal Ayurvedic formula containing gymnema showed significantly improved glucose control and reduced HbA1c levels in patients with type 2 diabetes within the 3-month test period.
Clinical note — Herbs and diabetes
Diabetes has been recognised since ancient times and as early as 700-200 BC two types of diabetes were recorded in India, one of which was diet related and the other was described as genetic. Diabetes has also been recognised in China for thousands of years, where it is attributed to yin deficiency and treated with an integrated approach that involves more than lowering blood glucose. At least 30 different herbal medicines are used in the management of diabetes and its complications, with several of these having outstanding beneficial potential.
HYPERCHOLESTEROLAEMIA AND HYPERTRIGLYCERIDAEMIA
Short-term animal studies have shown that gymnema extracts are able to reduce serum cholesterol and triglyceride levels in experimentally induced hyperlipidaemic rats and in spontaneously hypertensive rats, as well as in humans with type 2 diabetes. These results have not yet been established by long-term studies.
Gymnema has been used as a snake bite cure because it inhibits venom ATPase, and has also been used as a leaf paste to treat toe mycosis.