How we rate
“Strong” = several concordant meta-analyses or systematic reviews. “Moderate” = one synthesis, or several controlled trials. “Limited” = early trials only. The rating is about the quality of the studies, not about how useful the supplement is.
Ginseng
Asian (Panax ginseng) or American root: a slight effect on fasting blood glucose, on fatigue in certain patients and on the frequency of colds; nothing on physical performance. It reduces the effect of warfarin.
Benefits
- Slightly lowers fasting blood glucose: −0.31 mmol/l on average in a meta-analysis of 16 trials (770 people, diabetic or not), with no overall effect on HbA1c or insulin
- In type 2 diabetics or glucose-intolerants, improves fasting blood glucose and insulin resistance (meta-analysis of 8 trials), without changing HbA1c; in 19 well-controlled diabetics, 12 weeks of red ginseng lowered post-sugar-load blood glucose by 8 to 11 %
- Reduces cancer-related fatigue: in 364 fatigued survivors, 2,000 mg of American ginseng per day for 8 weeks improved the fatigue score by 20 points, against 10.3 under placebo
- Alleviates chronic fatigue of unknown cause: in 90 people, 2 g per day for 4 weeks moved the fatigue score from 7.3 to 4.4 out of 10, against 7.1 to 5.8 under placebo
- Fewer colds: over 4 months during flu season, 0.68 cold per person against 0.93 under placebo, and 10 % of people with at least two colds against 22.8 % (American ginseng extract, 279 adults)
- Erectile dysfunction: 2.4 times more favourable responses than under placebo in a meta-analysis of 6 red ginseng trials (349 men), from trials of low methodological quality
- Concentration: a single 200 mg dose improved mental calculation and reduced perceived mental fatigue during prolonged intellectual effort, in 30 young adults
Precautions
Anticoagulants: in 20 healthy volunteers, two weeks of American ginseng reduced the effect of warfarin (INR and blood warfarin levels down compared to placebo); if you take an anticoagulant, talk to your doctor before taking it. Possible interactions have also been reported with phenelzine and alcohol. In trials, ginseng alone does not cause more adverse effects than placebo: mostly headaches, sleep disturbances and digestive disorders; 65 trials report 135 minor events and none severe, and 4 weeks at 1 or 2 g per day changed no blood tests. Products that mix ginseng with other ingredients have been associated with severe events, without it being possible to say which was the cause. Limitations: reviews disagree — the 1999 review (16 trials) does not consider efficacy established for any indication, the 2011 review (57 trials) sees a clear effect on blood glucose but none on physical performance; the risk of bias remains unclear in most trials, and in 384 postmenopausal women, 16 weeks of ginseng did not change hot flushes.
Recommended dosage
200 to 400 mg of standardised extract per day, or 1 to 2 g of root extract; 2,000 mg of American ginseng (for fatigue) and 6 g of red ginseng (for diabetes) in trials
How to take it
- Who it is for: the clearest effects concern patients (type 2 diabetes, cancer-related fatigue, chronic fatigue); in healthy men, 8 weeks at 200 or 400 mg per day changed nothing during exertion.
- Blood glucose: in type 2 diabetics, 6 g per day of Korean red ginseng, at a rate of 2 g 40 minutes before each meal, for 12 weeks and in addition to usual treatment.
- Fatigue: 2,000 mg per day of American ginseng for 8 weeks (the difference with placebo was not significant at 4 weeks); 1 or 2 g per day of Panax ginseng extract for 4 weeks in chronic fatigue.
- Colds: two capsules per day of an American ginseng root extract for 4 months, starting from the beginning of the flu season; 200 mg twice a day in elderly people in care homes.
- Concentration: 200 or 400 mg of G115 extract in a single dose; 7 days of supplementation added nothing to the effect of a single dose.
- Which species: Asian ginseng (Panax ginseng, including red ginseng) and American ginseng (Panax quinquefolius) each have their own trials; no study in this profile compares them.
- What does not work: physical performance (oxygen consumption, lactate, heart rate unchanged), advanced cancer fatigue (no better than placebo in 4 weeks) and menopausal hot flushes.
Did you know?
Two weeks of American ginseng are enough to weaken the effect of warfarin, an anticoagulant: in 20 volunteers, INR and blood warfarin levels dropped compared to placebo.
What the studies say
This meta-analysis compiled the results of 8 randomized clinical trials evaluating the efficacy of ginseng in patients with type 2 diabetes or glucose intolerance. Ginseng showed no significant difference in HbA1c levels. However, it improved fasting blood glucose, postprandial insulin, and the HOMA-IR index, as well as triglyceride, total cholesterol, and LDL levels. The effect on fasting blood glucose was absent in patients on oral antidiabetics or insulin.
Gui QF, Xu ZR, Xu KY, Yang YM. — Medicine (2016) — View the source study
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