In a double-blind study, supplementation with American ginseng significantly reduced by 27% the number of colds that people experienced over a four-month period, compared with a placebo.⁴ The amount used in this study was 400 mg per day of a freeze-dried extract.

Numerous clinical trials indicate American ginseng (Panax quinquefolius) may improve insulin sensitivity and glucose metabolism.^6,7,8 Results from a placebo-controlled crossover study show a beneficial effect of 3 grams of American ginseng extract per day in participants with type 2 diabetes: eight weeks of treatment resulted in reductions in HgbA1c, fasting blood glucose levels, blood pressures, and LDL-cholesterol levels compared to placebo.⁹ In a twelve-week placebo-controlled trial that included 64 participants with type 2 diabetes and related high blood pressure, 3 grams of American ginseng per day resulted in decreased blood vessel stiffness and lower blood pressure.¹⁰ A typical dose used in clinical trials and found to be safe in those with type 2 diabetes is 1 gram three times daily.¹¹ Some American ginseng extracts are standardized for their ginsenoside content.

Extensive but often poorly designed studies have been conducted on the use of Asian ginseng (Panax ginseng) to improve athletic performance.^12[REF] While some early controlled studies suggested there might be benefits, several recent double-blind trials have found no significant effects of Asian ginseng on endurance exercise.^13,14[REF] In many studies, it is possible that ginseng was used in insufficient amounts or for an inadequate length of time; a more effective regimen for enhancing endurance performance may be 2 grams of powdered root per day or 200 to 400 mg per day of an extract standardized for 4% ginsenosides, taken for eight to twelve weeks.^[REF] Short-term intense exercise has also not been helped by Asian ginseng according to double-blind trials,^15,16 but one controlled study reported increased pectoral and quadricep muscle strength in non-exercising men and women after taking 1 gram per day of Asian ginseng for six weeks.¹⁷



An extract of a related plant, American Gingseng (Panax quinquefolius), was found ineffective at improving endurance exercise performance in untrained people after one week’s supplementation in a double-blind study.^[REF] Standardized extracts of American ginseng, unlike Asian ginseng, are not known. However, dried root powder, 1–3 grams per day in capsule or tablet form, can be used. Some herbalists also recommend 3–5 ml of tincture three times per day.