What is Gynostemma?

Antidiabetic Effect of Gynostemma Tea in Type 2 Diabetes

Gynostemma (Gynostemma pentaphyllum), a ginsenoside-containing plant, is used in traditional medicine in Vietnam. Pre-clinical studies have demonstrated a hypoglycemic effect attributed to phanoside,1 as well as antihyperlipidemic effects. In this double-blind, randomized, placebo-controlled, clinical trial, researchers have examined the antidiabetic effects of gynostemma tea in previously untreated patients with type 2 diabetes.

Between February and August 2007, the researchers recruited patients newly diagnosed with type 2 diabetes according to the criteria of the World Health Organization (WHO) from the outpatient population at the National Institute of Gerontology and 2 district hospitals in Hanoi, Vietnam.

The plants were decocted in boiling water for 2 hours, followed by precipitation of impurities by the addition of concentrated ethanol. After the ethanol was removed, the resulting extract was dried, ground into a brown powder, and provided to the patients in 3 g packets. The gynostemma tea contained 5% flavonoids and 18% saponins. Powdered green tea (Camellia sinensis) was used as the placebo and was supplied in a similar form and packaging. Green tea is not an ideal choice for a placebo because it possesses biological activities that include beneficial effects on glucose metabolism.2. Blood samples were taken on a weekly basis before, after, and during the study period.

All patients followed the study protocol and completed the study. The authors report no adverse events linked to either tea during the study period. The patients' age, gender, systolic and diastolic blood pressures, body weight, body mass index (BMI), waist and hip circumference, fasting plasma glucose levels, and HbA1c levels were not significantly different between the groups. Body weight and BMI were not significantly different from baseline after treatment in either group.

Following treatment, fasting plasma glucose significantly declined compared to baseline in the gynostemma group (P<0.001), but not in the placebo group. Post-treatment fasting blood glucose levels were significantly lower in the gynostemma group, when compared to the green tea group (P<0.01). The 30 and 120 minute oral glucose tolerance test results did not change significantly in either group. Levels of HbA1c decreased compared to baseline levels in both groups, but the gynostemma group experienced a greater change than the green tea group (P<0.001). The Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) results declined relative to baseline values to a greater degree in the gynostemma group than in the green tea group (P<0.05).

The authors conclude that gynostemma tea (6g/day) reduces hyperglycemia and is well-tolerated. They have previously shown that phanoside from gynostemma possesses insulin-releasing effects in pre-clinical studies,1 but this was not observed in this study. The results of this study suggest that the hypoglycemic mechanism may involve improvements in insulin resistance. Additional research is needed to confirm the results of this preliminary study, as well as to conclusively identify the relevant active constituents and to elucidate the mechanism of action.

Huyen VT, Phan DV, Thang P, Hoa NK, Ostenson CG. Antidiabetic effect of Gynostemma pentaphyllum tea in randomly assigned type 2 diabetic patients. Horm Metab Res. May 2010;42(5):353-357.

References
1Norberg A, Hoa NK, Liepinsh E, et al. A novel insulin-releasing substance, phanoside, from the plant Gynostemma pentaphyllum. J Biol Chem. Oct 1, 2004;279(40):41361-41367.
2Henson S. Control of obesity and diabetes among health benefits of green tea. HerbClip. May 31, 2010 (No. 051031-401). Austin, TX: American Botanical Council. Review of Beneficial effects of green tea: a literature review by Chacko SM, Thambi PT, Kuttan R, Nishigaki I. Chin Med. 2010;5:13. doi:10.1186/1749-8546-5-13.

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