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June 5, 2000 -- Stop before you pop that ginseng tablet if you're taking it to boost physical endurance. Ginseng seems to enhance certain components of the immune system, but claims that it boosts physical endurance in healthy people do not hold up, according to researchers at the University of Illinois at Chicago.
The term "ginseng" has been applied to more than 30 different species of plants, lead author Gail B. Mahady, PhD, and her colleagues write in a recent issue of Nutrition in Clinical Care. They concentrated on the Korean and Siberian varieties because those have been the focus of most previous studies.
Traditionally, Korean ginseng has been used as a tonic or immune stimulant for people recovering from chronic illnesses. The current practice of promoting it as a performance-booster in people who are already healthy is a "terrible mistake," Mahady tells WebMD.
"It has been used in traditional Chinese medicine in people more to restore health," she says. "It is never used in healthy individuals." Most of the trials showing a beneficial effect of Korean ginseng on physical endurance and capacity were so poorly performed that it is difficult to draw any conclusions from them, she and her co-authors write.
More promising are studies of the effects of Korean ginseng on the immune system. Two trials have shown that in healthy volunteers who take ginseng, certain immune cells are more numerous or more active than in people who take a placebo, or sugar pill.
For example, in a study of patients with bronchitis, a congestive lung disease, ginseng appeared to enhance the function of certain immune components in the bronchi, which are the main airways in the lungs. Mahady and her co-authors suggest ginseng may exert its effects on the body's stress response as well as the immune system.
There is some evidence that ginseng enhances immune activity in patients with AIDS and chronic fatigue syndrome, says Mahady, who is a research assistant professor at the university's College of Pharmacy. However, she tells WebMD that no good studies have yet confirmed its effect. "We really need to look at it in the elderly because there's a lot of chronic illness in that group," she says.
Russians traditionally have used Siberian ginseng to increase energy and decrease stress. However, most of the clinical trials suggesting that Siberian ginseng has an effect were performed decades ago and, like the studies of Korean ginseng, were poorly performed, the authors write. Because of this, it is difficult to conclude what effect, if any, Siberian ginseng has on endurance or physical performance. One study suggests that extracts of Siberian ginseng increase the number of working cells in the immune system in healthy volunteers when compared to people receiving a placebo.
Most of the side effects reported with Korean ginseng, such as high blood pressure, diarrhea, insomnia, and dizziness, have been reported in people who took very high doses -- some as high as 15 grams per day. This is well above recommended daily dose of 0.5 to 2 grams a day, Mahady and her colleagues write. A few cases of estrogenic-like side effects in pre- and postmenopausal women also have been recorded. The reports of side effects are hard to evaluate because they offer few, if any, details regarding the exact doses taken, or species of ginseng.
Siberian ginseng has been associated with high blood pressure and abnormal heart rhythm, and with low blood sugar in people with diabetes. Because good safety data are lacking, the authors do not recommend either form of ginseng for children or for pregnant or lactating women.
Unfortunately, labels are not always accurate, Mahady says, and it is hard for consumers to be certain how much ginseng actually is in the products they use.
Mahady urges people to learn as much as possible about the supplements they take and recommends a healthy dose of skepticism if a trial showing beneficial effects of ginseng happens to be sponsored by a company that manufactures it.
"I don't think ginseng is going to do anything for [people who are already healthy]," she says. "But it may help a patient with a chronic illness, as long as they don't have diabetes or high blood pressure."
For more WebMD information on alternative medicine, visit our Living Better Alternative Medicine page.
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作者： NorraMacReady 2006-8-16