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Review Questions Ginseng's Role in Exercise

American scientists who reviewed 35 recent in vivo studies of ginseng concluded that the quality of clinical research in this area is too low to serve as convincing evidence of ginseng's efficacy in improving human physical performance (Bahrke et al., 2000). The papers reviewed were animal and clinical studies utilizing a variety of ginseng species (including Korean [Panax ginseng C.A. Meyer, Araliaceae]; American [P. quinquefolius L.]; Vietnamese [P. vietnamensis Ha et Grushv]; and eleuthero, a.k.a. Siberian ginseng [Eleutherococcus senticosus (Rupr. ex Maxim.) Maxim, Araliaceae]) published between 1994 and 1999. Sixteen evaluated ginseng's effect on exercise performance in humans. The recent animal studies reviewed bolstered earlier findings that ginseng significantly increases aerobic endurance in rats and mice, apparently by altering the way the body uses fuel. One new finding indicates that ginseng also may boost animals' exercise performance by increasing muscle mass. Treatment with P. ginseng was associated with a positive effect on cognitive function in older rats and reduced signs of anxiety in rats and mice. However, human trials of ginseng often fail to confirm the positive effects observed in animal studies. The reviewers speculate that poor compliance rates, lower doses, or the failure of animal researchers to employ double-blind designs may explain this pattern.

The review focused on 16 clinical trials of ginseng's effect on exercise performance, most of which involved athletes or fit, healthy participants. Eleven studies utilizing various ginseng species reported that ginseng had no significant effect on any measures of psychological or physiological response to exertion. One study reported improved endurance, recovery time, and reaction time in people taking ginseng, but failed to present a statistical analysis of significance. The four remaining studies (two of which used a ginseng/fenugreek [Trigonella foenum-graecum L., Fabaceae] combination and two of which used E. senticosus) reported that ginseng treatment caused significant increases in aerobic performance, muscular strength, and endurance. Ginseng did not reduce blood lactate levels during exercise in any of the studies.

According to the review authors, these mixed results might be attributable to variations among ginseng species as well as the quality of ginseng preparations used, which may be affected by the plant's age and growing environment, season of harvest, and post-harvest processing. In the studies reviewed, researchers failed to use standardized preparations, failed to report these data, or relied on manufacturers' standardization claims instead of their own chemical analyses. The reviewers stressed that these and other problems are significant limitations to the credibility and repeatability of these studies. The authors also claim that recent analysis has suggested that methylxanthines such as caffeine, theophylline, and theobromine are present in ginseng in widely varying amounts and may influence study results. Ginseng does not contain caffeine. The research cited actually shows that some commercial ginseng supplements tested positive for caffeine, presumably because the product was formulated to contain caffeine. The authors of the review studies conducted no assays to determine levels of methylxanthine compounds in the test formulations they used.

In summary, the authors were highly critical of the current body of ginseng research, citing "numerous statistical and design problems" and "various methodological problems such as inadequate sample size and lack of double-blind, control and placebo paradigms." A number of trials used ginseng in combination with other ingredients (for example, herbs, vitamins, or high levels of alcohol) and/or did not specify the treatment dose, duration, or preparation. The reviewers assert that future research must address these issues before any conclusions may be drawn about ginseng's effects on human physical performance.

- Nancy Hoegler, Herb Research Foundation [Bahrke MS, Morgan WP. Evaluation of the ergogenic properties of ginseng. Sports Medicine 2000; 29(2): 113-133.]

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