Literature Briefs-With Analysis by Cydney E. McQueen, PharmD
American Ginseng for Postprandial Glycemia
Source: Vuksan V, et al. American ginseng (Panax quinquefolius L.) reduces postprandial glycemia in nondiabetic subjects and subjects with type 2 diabetes mellitus. Arch Intern Med 2000;160:1009-1013.
Objective: To determine the effects of American ginseng (Panax quinquefolius) on postprandial glycemia in nondiabetics and Type II diabetics.
Design and Setting: Randomized, placebo-controlled trial conducted at a hospital nutrition clinic in Toronto, Canada.
Subjects: Ten nondiabetic patients and nine reasonably well-controlled diabetic patients (mean HbA1c = 8.0).
Treatment: 3 g American ginseng or placebo with, or 40 minutes prior to, a 25 g/300 ml oral glucose load.
Dose/Route/Duration: 3 g American ginseng root or corn flour placebo capsules orally on four occasions separated by at least one week.
Outcome Measures: Changes in glycemia and area under the curve of glycemia, compared between treatment and placebo and between time of administration for treatment and placebo.
Results: In nondiabetic subjects, ginseng did not decrease glycemia more than placebo (P = 0.06), although when effect of time of administration was compared, taking the dose 40 minutes prior to glucose load did lower glucose significantly (P = 0.02).
In diabetic patients, treatment resulted in a significant lowering of blood glucose (P = 0.008) vs. placebo, but time of administration made no difference in amount of decrease achieved (P = 0.2).
One patient reported mild insomnia on one occasion after receiving one of the two ginseng doses; no other side effects occurred. Authors provided discussion of doses used and possible mechanisms by which ginseng could be affecting glucose levels, and concluded that the actual clinical relevance of their findings is as yet "debatable."
Strengths/Limitations: Researchers used appropriate measures for determination of glucose levels and appropriate statistical analysis of results, but no a priori power calculation was performed. In several instances information was not provided. For example, there was no discussion of inclusion/exclusion criteria or postrandomization similarity of groups. Likewise, great care was taken to ensure that treatment and placebo capsules were identical, even to the protein and carbohydrate content, but no mention is made of whether the study was actually double-blinded. The investigators stated they were examining effects on "postprandial" glycemia, but ran tests on an oral glucose solution, few people’s idea of a "meal." It is unknown if actual food could have changed results in any way.
Comments: The study provides information on a specific effect of American ginseng, i.e., that it will decrease glycemia after an oral glucose load, but does not address clinical effectiveness, e.g., whether it can help diabetic patients to control blood sugar levels with long-term use.
Clinical Impact: Results are very promising, but more information is needed on long-term effects and efficacy before a firm recommendation can be made. Type II diabetics taking hypoglycemic medications should use American ginseng with extra caution to avoid hypoglycemic reactions.
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