The genus Panax includes eleven species, of which nine are native to eastern Asia and two to eastern North America. They are perennial herbs with a few palmately compound leaves and with small flowers, borne in a single umbel, that develop into a cluster of red berries. The most commonly used species are Panax ginseng C. A. Mey. (Asian Ginseng) and P. quinquefolium L. (American Ginseng). Both species have elongated, tapering taproots that sometimes branch at the base, giving a fancied resemblance to the human form (hence the common name ?man-root,? or ?ren-seng? in Chinese). Asian ginseng root has been used for millennia in Chinese medicine as a general tonic for the elderly or debilitated. There are a number of traditional preparations, such as Korean red ginseng, in which the roots are steamed or soaked using various recipes; roots at least five years old are preferred for these products. Much ginseng is wild-collected, both because it can be difficult to cultivate and because Asian consumers prefer roots with the gnarled shape of woods-grown ginseng. Excessive collection from the wild may threaten both species? survival; in the eastern United States, poaching from both public and private land is a serious problem. Because of ginseng?s high value and scarcity, powdered ginseng has often been adulterated with valueless plant material, and the buyer must still beware.

Ginseng root has been shown to effectively reduce hyperglycemia in people and test animals with diabetes; the berries and leaves of American ginseng have a similar effect in animal studies. Scientific evidence for the traditional tonic usage is limited by comparison, although general feelings of well-being can be difficult to measure. Several clinical trials have tested the use of ginseng to improve performance in young healthy subjects; it seems to be clearly ineffective for that purpose. A few studies have demonstrated positive effects in certain conditions (e.g., COPD, erectile dysfunction) or increased immune responses. Several animal and epidemiological studies suggest that consumption of ginseng products may inhibit the development of certain cancers. Among the active compounds are a group of saponins known as ginsenosides. Each species contains a suite of ginsenosides, whose individual bioactivities are not equivalent. For example, one ginsenoside, if consumed alone in large quantities, might lower blood pressure, while another would raise it. This has been seen as an explanation for ginseng?s supposed ability to bring the body into balance from a variety of starting conditions. There is some evidence that roots at least five years old are more potent, at least in animal cancer-prevention studies, confirming the traditional preference for these roots. (There is, however, no scientific evidence that wild roots are more potent than cultivated roots.) Ginseng usually has mild side effects; the once-alleged ?ginseng abuse syndrome? is either nonexistent or not relevant to ordinary consumers. However, ginseng may have drug interactions, especially with pharmaceuticals for diabetes. It may also reduce the effectiveness of warfarin, although the evidence from two human studies is conflicting.

Selected References

Choi, H. K., and J. Wen. 2000. A phylogenetic analysis of Panax (Araliaceae): integrating cpDNA restriction site and nuclear rDNA ITS sequence data. Pl. Syst. Evol. 224:109-120.

Gross, D., Z. Shenkman, B. Bleiberg, M. Dayan, M. Gittelson, and R. Efrat. 2002. Ginseng improves pulmonary functions and exercise capacity in patients with COPD. Monaldi Arch. Chest Dis. 57:242-246.

Hong, B., Y. H. Ji, K. Y. Nam, and T. Y. Ahn. 2002. A double-blind crossover study evaluating the efficacy of korean red ginseng in patients with erectile dysfunction: a preliminary report. J. Urol. 52:20-21.

Kiefer, D., and T. Pantuso. 2003. Panax ginseng. Am. Fam. Physician 15:1539-1542.

McGraw, J. B. 2001. Evidence for decline in stature of American ginseng plants from herbarium specimens. Biol. Conserv. 98:25-32.

McGraw, J. B., and M. A. Furedi. 2005. Deer browsing and population viability of a forest understory plant. Science 307:920-922.

Scaglione, F, G. Cattaneo, M. Alessandri, and R. Cogo. 1996. Efficacy and safety of the standardised Ginseng extract G115 for potentiating vaccination against the influenza syndrome and protection against the common cold [corrected]. Drugs Exp. Clin. Res. 22:65-72 [erratum 22: 338].

Wen, J. 2001. Species diversity, nomenclature, phylogeny, biogeography, and classification of the ginseng genus (Panax L., Araliaceae). Pp. 67-88 in: Punja, Z. K., ed. Utilization of biotechnological, genetic and cultural approaches for North American and Asian ginseng improvement, Proceedings of the International Ginseng Workshop. Simon Fraser University Press, Vancouver.

Yun, T. K. 2003. Experimental and epidemiological evidence on non-organ specific cancer preventive effect of Korean ginseng and identification of active compounds. Mutat. Res. 523-524:63-74.

Yun, T. K., Y. S. Lee, Y. H. Lee, S. I. Kim, and H. Y. Yun. 2001. Anticarcinogenic effect of Panax ginseng C. A. Meyer and identification of active compounds. J. Korean Med. Sci. 16 Suppl:S6-S18.