Panax ginseng

2011

(Ginseng)

Several plants of the Panax genus are commonly referred to as ginseng. Ginseng (Panax ginseng) was used by the Chinese as an aphrodisiac because its forked roots resemble the lower part of the human body. Native Americans brewed a type of tea from one species, Panax quinquefolius, and they ate the roots of the dwarf ginseng, Panax trifolius. Some plants referred to as Siberian, Manchurian and Brazilian ginseng do not belong to the Panax genus and so may not contain the agents in Panax ginseng to which its effects are attributed. The term ginseng usually refers to Panax ginseng also called Chinese or Korean ginseng and this is the most commonly used and tested variety of ginseng. It has been suggested that as many as six million Americans may use ginseng preparations.

The name of the genus Panax is derived from the Greek word for panacea meaning ‘all healing’ and it is suggested that ginseng preparations have a number of diverse effects that promote general well-being. The active principles of ginseng are believed to be substances called ginsenosides which are saponins consisting of a steroidal triterpene and a sugar residue (triterpene glucuronides). Around a dozen of these ginsenosides have been identified in ginseng extracts. Some of the claimed benefits for ginseng include:

• As a tonic to restore strength and promote general well-being

• To improve physical performance

• To improve memory and mental well-being

• To help prevent cancer

• To aid in the treatment of diabetes.

Vogler et al. (1999) did a systematic review of randomised controlled clinical trials of ginseng for a variety of possible uses. They identified sixteen trials of sufficient quality to meet their inclusion criteria and they found that these trials provided no compelling evidence for the efficacy of ginseng for any of the indications tested, that is:

• For enhancing physical performance

• For improving mental performance or memory

• For enhancing the immune system or for the treatment of infection with the herpes simplex virus

• In the management of diabetes.

Bucci (2000) lists (with references) a wide range of pharmacological activities that have been reported for the ginsenosides present in ginseng (extracts) usually on the basis of animal or in vitro studies, including:

• Some ginsenosides have central nervous system (CNS) stimulating effects whilst others have depressant effects.

• They cause increased release of corticotrophin from the pituitary and thus increased cortisol output (the so-called ‘stress hormone’) from the adrenal glands.

• They have modulating effects upon the immune system.

• They have antioxidant effects via an increase in the glutathione content of the liver.

• They stimulate nitric oxide production at various sites.

Cardinal and Engels (2001) tested the effects of two doses of ginseng on ‘psychological well-being’ in a randomised controlled trial using 80 students. They measured the subjects’ responses in psychological mood and well-being evaluation tests before and after two months of taking the ginseng or placebo. They found no significant effect of the ginseng at either dose.

Of all the herbs claimed to enhance physical athletic performance, ginseng is probably the most tested. There is a significant body of animal data suggesting that ginsenosides can induce improvements in exercise performance in controlled laboratory experiments with small mammals. However, most of these studies have used very large doses and/or injected the ginsenosides. Ginsenosides are known to undergo chemical conversion in the gut and so the injection studies, in particular, may have little application to oral use by people. Reviews by Bahrke and Morgan (1994; 2000) found no consistent evidence for an ergogenic effect of ginseng and this is consistent with the view of most reviewers. Bucci (2000) reviewed the literature relating to the effect of a number of herbal preparations upon human performance. He provides an extensive tabulated list of studies that have tested the effects of Panax ginseng upon human physical and mental performance. Like other reviewers he notes the inconsistency of these trials but goes on to suggest that those studies with positive outcomes have almost invariably used high doses (the equivalent of at least 2 g/day of dried root) and were of long duration (at least eight weeks). He further suggests from his overview of published trials that any benefits of ginseng may be largely confined to older, untrained subjects. He concludes that young, trained individuals probably get little if any benefit from ginseng on their physical performance and that any effects there may be in older, untrained subjects require large doses to be used over an extended period. On the basis of a limited amount of low quality data he concludes that Siberian ginseng, which is not a Panax species, has little or no ability to improve aerobic performance in trained individuals.

There is some evidence from case-control studies and from one cohort study that regular consumption of ginseng is associated with a reduced incidence of cancer (not site specific). Yun and Choi (1998) evaluated the ginseng intake of 4600 middle-aged and elderly Koreans and related this to their risk of developing a cancer over the following five years. Those people who consumed ginseng had a significantly lower risk of developing cancer than those who did not. Over the five years of the study there were 48 cases of cancer per thousand people in the ‘no ginseng‘ group compared with 24 cases per thousand in the ginseng group. Whilst these data look interesting it should be borne in mind that epidemiological association does not necessarily indicate cause and effect. The Koreans who consumed the ginseng (70% of the sample) were a self-selecting group and although they had a lower risk of cancer than those who did not, it would be premature to attribute this effect to the ginseng per se. Yun (2001) has reviewed evidence of the cancer-preventing effects of Panax ginseng.

In a review of the risks and benefits of several herbal therapies, Ernst (2002) identified several serious but probably uncommon side-effects reported by people taking ginseng including:

Insomnia and nervousness

Diarrhoea

• Skin eruptions

• Headaches

• Symptoms associated with oestrogenic activity such as breast tenderness and vaginal bleeding in postmenopausal women (probably making it unsuitable for women with breast cancer).

There are some reports that ginseng may reduce the effectiveness of anticoagulant (warfarin) therapy. These potential side-effects need to be borne in mind if large supplemental doses are used for extended periods. There is a long history of ginseng use in foods and drinks, however, provided usage is moderate there seems no reason to discourage such use by most people. People who enjoy its culinary use can be assured that there is no reason to stop using it and that there is just the possibility that it may be beneficial. There is no established dose for supplemental use but manufacturers recommend the equivalent of 0.5-3 g/day of the dried root. One quality UK supplier produces tablets that contain the equivalent of 600 mg of Korean ginseng root guaranteed to contain at least 18 mg of ginsenosides.