Ashwagandha, Withania somnifera, is an adaptogenic herb with a 3000-year history in Ayurvedic medicine that has accumulated a more substantial clinical trial database than most botanical supplements. An adaptogen is defined as a substance that non-specifically increases resistance to stress without producing side effects at therapeutic doses. The active constituents of ashwagandha, withanolides, have documented effects on the HPA axis, the hormonal stress response system, and on the GABAergic system that regulates anxiety and sleep.
Cortisol Reduction: The Trial Evidence
A double-blind randomised controlled trial by Chandrasekhar et al. in adults with chronic stress found that ashwagandha extract at 300mg twice daily for eight weeks produced a 27 percent reduction in serum cortisol compared to placebo, alongside significant improvements in perceived stress, anxiety, and sleep quality. A separate trial by Choudhary et al. using KSM-66, a standardised root extract, found similar cortisol reductions alongside improvements in subjective wellbeing. The consistency across trials using different formulations is notable.
Sleep Quality
A double-blind placebo-controlled trial specifically examining ashwagandha and sleep found that 300mg of KSM-66 twice daily for 10 weeks significantly improved sleep quality, sleep onset latency, total sleep time, and sleep efficiency compared to placebo in adults with insomnia. The proposed mechanism involves the GABA receptor modulating effects of withanolides and the reduction in cortisol that otherwise disrupts sleep architecture.
Physical Performance
Ashwagandha has evidence for physical performance improvement beyond its stress-modulating effects. A study by Wankhede et al. in resistance-trained men found that 300mg twice daily for eight weeks produced significantly greater increases in muscle strength, recovery, and testosterone levels compared to placebo. A meta-analysis of ashwagandha and physical performance confirmed significant benefits in VO2 max, muscle strength, and recovery time across multiple trials.
- KSM-66 and Sensoril are the two most studied standardised extracts: use these rather than generic ashwagandha root powder
- Effective doses in trials: 300mg twice daily or 600mg once daily of a standardised extract
- Benefits are cumulative and typically require four to eight weeks of consistent use
- Take with food: fat-soluble withanolides absorb better with a meal
- Ashwagandha is generally well tolerated, but is contraindicated in pregnancy and in thyroid disease requiring monitoring
Sources
- Chandrasekhar, K., et al. (2012). A prospective, randomized double-blind, placebo-controlled study of safety and efficacy of a high-concentration full-spectrum extract of ashwagandha root in reducing stress and anxiety in adults. Indian Journal of Psychological Medicine, 34(3), 255-262.
- Langade, D., et al. (2019). Efficacy and safety of ashwagandha root extract in insomnia and anxiety in adults. Medicine, 98(37), e17186.