Ashwagandha

Human RCT Supplementsperformance hormonal Last reviewed 2026-09-28

Summary

Withania somnifera, a plant used in Ayurvedic medicine. Randomized trials report reduced perceived stress and cortisol with daily root extracts, and one trial in men doing resistance training reported greater strength gains than training plus placebo.

Mechanism

Withania somnifera root extracts contain withanolides, steroidal lactones hypothesized to modulate the hypothalamic-pituitary-adrenal axis and GABAergic signaling. Human trials are consistent with a stress-buffering effect: lower perceived stress and modestly lower cortisol, which could indirectly support training consistency and recovery, though the performance mechanisms remain inferred rather than demonstrated.

Reported effects

Ratings are relative to peers in the same category, not absolute claims.

Perceived stress and anxiety★★★☆☆Small trials report lower stress scores vs placebo; replicated across a few RCTs.

Serum cortisol★★★☆☆Chandrasekhar and Lopresti reported lower cortisol vs placebo; small samples.

Strength with resistance training★★☆☆☆One 8-week RCT in men found greater bench/squat gains than training plus placebo.

Testosterone in men★★☆☆☆Limited to small trials in men; not consistent enough to treat as established.

Studied dosing: research context

Trials most commonly use 250-600 mg/day of standardized root extract for 8-12 weeks. The stress trials used 300 mg twice daily (600 mg/day) for 60 days; the strength trial used 300 mg twice daily for 8 weeks alongside resistance training. These are doses used in research, not guidance.

Research context only. This is not a recommendation.

Safety

Trials generally report mild side effects (gastrointestinal discomfort, headache) at rates similar to placebo. Isolated case reports exist of liver injury and of thyroid hormone changes, so people with thyroid conditions or on thyroid medication are often advised in the literature to use caution. Human data in pregnancy are lacking, and animal data do not support use.

Limitations

Trials are small, mostly 8-12 weeks, and some were industry-funded. Extract standardization (withanolide content) varies across products, so results may not generalize between brands. Long-term safety data are thin. Testosterone and strength findings rest on a handful of small studies in men.