July 01, 2003 Volume 39 Issue 26

Ginseng may lower blood glucose

By Caroline Helwick

NEW ORLEANS – Ginseng may improve the control of blood sugar in patients with type 2 diabetes, say University of Toronto investigators during presentations at the American Diabetes Association annual meeting.

Dr. Vladimir Vuksan (PhD), lead investigator, and colleagues, previously showed American ginseng could improve acute and long-term glycemic control. The current studies involved American ginseng from a variety of Canadian farms as well as Korean red ginseng supplied directly by manufacturers in Korea.

Glycemic targets continue to be unmet in the majority of patients with type 2 diabetes, and better management strategies are needed, said investigators. This need coincides with an increase in the use of complementary and alternative medicine in a manner largely unregulated or examined.

"Our clinic has attempted to answer this call" by rigidly investigating an alternative treatment that appears to hold some promise in blood glucose lowering, said Dr. Vuksan, associate professor of endocrinology and nutritional sciences and associate director of the Risk Factor Modification Centre at the University of Toronto.

The investigators conducted a series of acute batch and dose-finding trials with Korean red ginseng rootlets, then used the most efficacious batch and dose from this testing in a long-term randomized, double-blind, placebo-controlled trial in patients with type 2 diabetes.

The study included 19 well-controlled type 2 diabetic subjects who received 6 g/day of Korean red ginseng or placebo along with their conventional diabetes treatment. After 12 weeks of treatment, metabolic control was significantly improved in subjects receiving the ginseng.

Patients receiving ginseng had a 40% reduction in both fasting and postprandial plasma insulin and improvements in hepatic insulin sensitivity and whole body insulin sensitivity, compared with placebo.

Co-investigator John Sievenpiper said not all types of ginseng nor all batches of Korean red ginseng have glycemic-lowering efficacy.

"We have to be cautious what we tell people. . . . We don't know if these results are even reproducible because ginseng varies so much from batch to batch."

The efficacy of ginseng was found to be related to the particular profile of ginsenosides (steroidal glycosides) within the ginseng rootlets. While no dose-response emerged, per se, doses from 4 g to 6 g most significantly lowered incremental glycemia.

In a further investigation, American ginseng was combined with konjac mannan, a highly viscous fibre similar to pectin that is consumed as a food in Japan and is not available in North America. It seems to slow the rate of absorption of glucose, explained the lead investigator of this study, Alexandra Jenkins, a research associate.

The double-blind, placebo-controlled crossover study enrolled 30 well-controlled type 2 diabetics, 23 of whom were being treated with oral hypoglycemic agents and seven of whom were using lifestyle intervention alone, for management of diabetes. The participants were randomly assigned to receive either a blend of 3 g American ginseng plus 7 g of konjac, or placebo, daily for 12 weeks.

The main endpoint, hemoglobin A1c, decreased after six weeks in both arms, but this reduction was sustained to 12 weeks only in the ginseng/konjac arm. At that time, hemoglobin A1c had dropped from a mean baseline level of 7.0% to 6.5% in ginseng/konjac users, compared to 6.8% in placebo recipients, Jenkins said.