200–400 mg/day of extract standardized to ginsenosides.
Possible slight improvement in glycemic control.
View the study (meta-analysis) →⏱ 3 min read
Asian ginseng (Panax ginseng) and American ginseng (Panax quinquefolius) are two closely related species that traditional Chinese and Korean medicine have used for millennia as general tonics for vitality, longevity, and recovery from fatigue; the word "panax" comes from the Greek and means "panacea," an ambitious name that modern pharmacology has qualified with a more modest but clinically real activity profile in several specific indications.
The main active compounds are ginsenosides, a family of triterpenoid saponins with more than 40 identified variants, which act on multiple receptors and cellular pathways (including modulation of the hypothalamic-pituitary-adrenal axis, nitric oxide, mitochondrial function, and immunity); the ginsenoside composition varies between species, between parts of the root, between processing methods (white ginseng vs. red ginseng), and between commercial products, which makes it difficult to compare clinical results across studies that used different preparations.
The indication with the best evidence is fatigue related to chronic stress, illness, or aging: several randomized trials have shown that doses of 1,000 to 3,000 milligrams daily of standardized Panax ginseng extract for 4 to 12 weeks improve the sense of mental energy, sustained concentration, and overall well-being in people with clinically significant fatigue, including cancer survivors and patients with chronic fatigue.
In healthy people, the effects on "normal" cognition are more modest and heterogeneous, but some studies show improvements in processing speed, working memory, and performance on demanding cognitive tasks with doses of 200 to 400 milligrams daily; the effect usually appears within the first weeks and persists for as long as supplementation continues, without the rapid habituation seen with stimulants such as caffeine.
A well-studied indication for Korean Panax ginseng (the red variant, subjected to specific processing that alters the ginsenoside profile) is mild to moderate erectile dysfunction: several randomized trials and a meta-analysis have shown significant improvements on scales such as the IIEF with doses of 900 mg to 3 grams daily over 8 to 12 weeks, a modest but replicable effect that makes it a reasonable option for men with mild problems who prefer to avoid drugs such as sildenafil.
The most plausible mechanism combines improved endothelial function via nitric oxide, effects on the central nervous system that reduce performance anxiety, and possibly a modest hormonal modulation of testosterone; the magnitude of the effect is smaller than that of PDE5 inhibitors but sufficient as a first line in men with problems of psychological or mild vascular origin.
In type 2 diabetes, several trials have shown modest reductions in fasting blood glucose and HbA1c with 1-3 grams daily of American ginseng (Panax quinquefolius) over 8-12 weeks, an effect that adds to standard treatment without generating relevant drug interactions in the available studies.
In cold prevention, Panax quinquefolius (American ginseng) in particular has shown 25-50 percent reductions in the frequency and severity of viral respiratory infections during the winter with long-term use at low doses; this immunomodulatory effect appears to be related to changes in T and NK cells described in mechanistic studies.
The doses studied range from 200 mg to 3 grams daily depending on indication and species: 200-400 mg/day to improve cognition and well-being in healthy people, 1-3 g/day for clinical fatigue or erectile dysfunction, 200-400 mg/day of Panax quinquefolius for seasonal immunity; ideally taken in the morning because it can be activating and cause insomnia if taken late, especially the Asian varieties.
Generally well tolerated in the short term; the most frequent adverse effects are insomnia (if taken late), nervousness, palpitations at high doses and, in women, occasionally dysfunctional vaginal bleeding from a modest estrogenic effect; people taking warfarin should exercise caution because of a described interaction (potentially reducing the anticoagulant effect), those taking serotonergic antidepressants or MAOIs should consult first, and it is advisable to avoid it in pregnancy, breastfeeding, and decompensated psychiatric disorders.
Information, not medical advice. Scientific evidence reflects the quality of the studies.