From the Spring 2002 Issue of Nutrition Science News
David Wolfson, N.D.
Practitioners of Eastern medicine have long revered ginseng (Panax spp.) as an effective treatment for numerous health conditions. Western researchers are beginning to unravel the specific benefits of the herb, including new findings that show American ginseng (P. quinquefolius) to be an effective blood-glucose modulator. Researchers have suggested that ginseng exhibits a hypoglycemic effect in animals, [1,2] and new human trials are validating the claim.
Three new studies, performed jointly by researchers at the University of Toronto, St. Michael's Hospital in Toronto, and the University of Ottawa, show that American ginseng can lower blood-sugar levels in diabetic and nondiabetic patients. [3-5]
In the first study, researchers gave nine subjects with type II diabetes and 10 nondiabetic subjects either 3 g American ginseng or placebo, followed by a 25 g oral glucose solution. Both ginseng groups experienced an 18 percent to 22 percent reduction in postprandial glycemia (blood-sugar levels after carbohydrate consumption) compared with placebo. In the nondiabetic subjects, ginseng lowered postprandial blood sugar only when taken 40 minutes prior to the glucose challenge. In diabetic subjects, ginseng lowered postprandial sugar whether administered 40 minutes prior to, or together with, the glucose challenge.
In the second study, researchers compared different doses of American ginseng3, 6 and 9 gin diabetic subjects. They found that ginseng caused the same postprandial blood-sugar lowering results at each dose, and at any time from 0 to 120 minutes before the glucose challenge.
Researchers in the third study aimed to replicate the first two studies' results using a lower ginseng dose in nondiabetic patients. Twelve healthy individuals received 1, 2 or 3 g American ginseng or placebo at 40, 20, or 10 minutes before or along with a glucose challenge. They found no significant differences between the three doseseach lowered postprandial glucose levels an average of 11.4 percent. As in the first study, ginseng was effective only when taken 40 minutes prior to the glucose challenge.
The somewhat disparate results of these three studies can be summarized as follows: In both healthy and diabetic people, doses as small as 1 g American ginseng can lower the glycemic response after carbohydrate consumption. Although administration time does not seem to be an issue for diabetics, ginseng regulates glycemia in healthy people most effectively when taken 40 minutes before carbohydrate consumption.
The results of these studies are important because of mounting evidence that postprandial hyperglycemia poses a significant health risk to both diabetic and nondiabetic people. Poor control of postprandial glucose levels is a diabetic risk factor for developing vascular complications, such as atherosclerosis,  and researchers have found that nondiabetics with higher postprandial blood-sugar levels were more likely to develop diabetes and to die of cardiovascular disease. 
Questions remain as to the mechanisms behind ginseng's hypoglycemic action. The Toronto researchers concluded from animal experiments that ginseng slows digestion, stimulates insulin secretion, and enhances nitric oxide-mediated uptake of glucose into cells.  Each of these mechanisms offers a plausible explanation for ginseng's ability to lower blood-glucose levels, although the latter two mechanisms may better explain why ginseng works in nondiabetics when taken 40 minutes prior to a glucose challenge.
Further research is needed to determine ginseng's optimal dose and whether other species, such as P. ginseng or P. notoginseng, are equally effective in modulating blood-glucose levels. Until then, it is safe for those concerned about glycemic control to take 1 to 3g American ginseng, in capsules or as a tea, at least 40 minutes prior to a meal with carbohydrates. It will probably become evident with further research that specific timing of ginseng intake is not necessary and that regular use between meals (e.g., 1 g, three times/day) is sufficient to provide ongoing blood-sugar control.
David Wolfson, N.D., is a naturopathic physician, nutrition educator and consultant to the natural products industry.
1. Martinez B, et al. The physiological effects of Aralia, Panax and Eleutherococcus on exercised rats. Jpn J Pharmacol 1984;35:79-85.
2. Ng TB, et al. Hypoglycemic constituents of Panax ginseng. Gen Pharmacol 1985;16:549-52.
3. Vuksan V, et al. American ginseng (Panax quinquefolius L.) reduces postprandial glycemia in nondiabetic subjects and subjects with type II diabetes mellitus. Arch Intern Med 2000;160:1009-13.
4. Vuksan V, et al. Similar postprandial glycemic reductions with escalation of dose and administration time of American ginseng in type II diabetes. Diabetes Care 2000;23:1221-6.
5. Vuksan V, et al. American ginseng (Panax quinquefolius L.) attenuates postprandial glycemia in a time-dependent but not dose-dependent manner in healthy individuals. Am J Clin Nutr 2001;73:753-8.
6. Ceriello A. The postprandial state and cardiovascular disease: relevance to diabetes mellitus. Diabetes Metab Res Rev 2000;16:125-32.
7. Balkau B, et al. High blood glucose concentration is a risk factor for mortality in middle-aged nondiabetic men. Diabetes Care 1998;21(3):360-7.