American ginseng (Panax quinquefolius L.) attenuates postprandial glycemiain a time-dependent but not dose-dependent manner in healthy individuals

Background: We previously showed that 3 g American ginseng administered 40 min before an oral glucose challenge significantly reduces postprandial gly cemia in subjects without diabetes. Whether this effect can be replicated w ith doses <3 g and administration times closer to the oral glucose challeng e is unclear. Objective: Our objective was to study the dosing and timing effects of Amer ican ginseng on postprandial glycemia. Design: In a random crossover design, 12 healthy individuals [<(<chi>)over bar> +/- SEM age: 42 +/- 7 y; body mass index (BMI; in kg/m(2)): 24.1 +/- 1 .1] received 16 treatments: 0 (placebo), 1, 2, or 3 g American ginseng at 4 0, 20, 10, or 0 min before a 25-g oral glucose challenge. Capillary blood w as collected before administration and at 0, 15, 30, 45, 60, and 90 min aft er the start of the glucose challenge. Results: Two-way analysis of variance showed that the main effects of treat ment and administration time were significant (P < 0.05). Glycemia was lowe r over the last 45 min of the test after doses of 1, 2, or 3 g ginseng than after placebo (P < 0.05); there were no significant differences between do ses. The reductions in the areas under the curve for these 3 doses were 14. 4 +/-: 6.5%, 10.6 +/- 4.0%, and 9.1 +/- 6%, respectively. Glycemia in the l ast hour of the test and area under the curve were significantly lower when ginseng was administered 40 min before the challenge than when it was admi nistered 20, 10, or 0 min before the challenge (P < 0.05). Conclusions: American ginseng reduced postprandial glycemia in subjects wit hout diabetes. These reductions were time dependent but not dose dependent: an effect was seen only when the ginseng was administered 40 min before th e challenge. Doses within the range of 1-3 g were equally effective.