Ginseng is most often claimed to help improve physical and mental performance or to function as an “adaptogen,” an agent that helps the body to return to normal when exposed to stressful or noxious stimuli. However, the clinical trials evaluating ginseng for these indications have shown few, if any, benefits. Some randomized controlled trials evaluating “quality of life” and “cognition” have claimed significant benefits in some subscale measures of behavior, cognitive function, or quality of life but rarely in overall composite scores using P ginseng. Better results have been observed with P quinquefolium and P ginseng in lowering postprandial glucose indices in subjects with and without diabetes. This was the subject of a systematic review in which 15 studies (13 randomized and 2 nonrandomized) were evaluated. Nine of the studies reported significant reductions in blood glucose. Some randomized, placebo-controlled trials have reported immunomodulating benefits of P quinquefolium and P ginseng in preventing upper respiratory tract infections. Use of ginseng for 2–4 months in healthy seniors may reduce the risk of acquiring the common cold as well as the duration of symptoms. Because of heterogeneity in these trials, however, the findings are insufficient to warrant a recommendation of ginseng for cold prevention. To assess effects on cardiovascular health, a systematic review and meta-analysis of 17 randomized controlled trials involving predominantly P ginseng (12 studies) and P quinquefolium (5 studies) species in persons with and without hypertension was performed. Over a mean time period of 9 weeks, no significant effect was observed of ginseng on SBP, DBP, and mean arterial pressure compared with controls. Finally, two case-control studies and a cohort study suggest a non-organ-specific cancer-preventive effect with longterm administration of P ginseng. Significant benefits in some cancer-related fatigue symptoms have been observed in both a dose-finding study and a multisite, double-blind, randomized trial using P quinquefolium, 2 g daily, versus placebo over a 2-month period. In summary, the strongest support for use of P ginseng or P quinquefolium currently relates to its effects in cold prevention, lowering postprandial glucose, nonspecific cancer prevention, and alleviating cancer-related fatigue.
Vaginal bleeding and mastalgia have been described in case reports, suggesting possible estrogenic effects. Central nervous system stimulation (eg, insomnia, nervousness) and hypertension have been reported in patients using high doses (>3 g/d) of P ginseng. Methylxanthines found in the ginseng plant may contribute to this effect. Vasoregulatory effects have not been found to be clinically significant.
Irritability, sleeplessness, and manic behavior have been reported in psychiatric patients using ginseng in combination with other medications (phenelzine, lithium, neuroleptics). Ginseng should be used cautiously in patients taking any psychiatric, estrogenic, or hypoglycemic medications. Ginseng has antiplatelet properties and should not be used in combination with warfarin. Cytokine stimulation has been claimed for both P ginseng and P quinquefolium in vitro and in animal models. In a randomized, double-blind, placebo-controlled study, P ginseng significantly increased natural killer cell activity versus placebo with 8 and 12 weeks of use. Immunocompromised individuals, those taking immune stimulants, and those with autoimmune disorders should use ginseng products with caution.
A dose of 1–2 g/d of the crude P ginseng root or its equivalent is considered standard dosage. Two hundred milligrams of standardized P ginseng extract are equivalent to 1 g of the crude root. The trademarked preparation Ginsana has been used as a standardized extract in some clinical trials and is available in the USA.