Panax Ginseng: Benefits for Men, Dosage and Side Effects

Ginsenosides, of which more than a hundred have been identified, with Rb1 and Rg1 the most studied. Proposed actions include modulation of the hypothalamic-pituitary-adrenal axis, nitric oxide release in vascular and erectile tissue, and effects on mitochondrial function relevant to fatigue.

• Fatigue: meta-analyses find Panax ginseng superior to placebo on fatigue scales and heart-rate recovery, with mental fatigue the most consistently improved measure. 2 g/day reduced visual analogue fatigue scores against placebo.
• Erectile function: contested. Cochrane rated the effect trivial on the IIEF-15; red-ginseng-specific meta-analysis found a risk ratio of 2.40, in low-quality trials.
• Glycaemic measures: modest improvements in some trials.
• Immune function: preliminary.

A Cochrane systematic review of ginseng for erectile dysfunction, Jang 2008 meta-analysis of red ginseng in the same indication, and a systematic review of Panax ginseng across randomised controlled trials. Fatigue is where the evidence is most consistent; erectile function is where it is most cited and least settled.

200 mg to 3 g/day of root or standardised extract. Fatigue trials commonly used 2 g/day. Extracts standardised to 3-5% ginsenosides are the usual supplement format. Cycling four weeks on and two weeks off is a traditional practice rather than an evidence-based one.

Insomnia is the most common, which argues for morning dosing. Headache, GI upset, nervousness and blood pressure changes in either direction. Occasional reports of menstrual irregularity and breast tenderness.

May reduce the effect of warfarin. Additive with glucose-lowering medication, with a hypoglycaemia risk. Interacts with MAO inhibitors, notably phenelzine. Stimulant effects add to caffeine. Should be stopped before surgery because of effects on bleeding and blood glucose.