Ashwagandha (Withania somnifera)
Ashwagandha is an adaptogenic root extract from Withania somnifera, standardised to withanolides, used for stress reduction, sleep and modest ergogenic and hormonal effects. It has more human RCT support than almost any other herbal 'T-booster', but the testosterone signal is small and inconsistent, and the strongest, most reproducible finding is lowered cortisol and self-reported stress. Marketed heavily under branded extracts such as KSM-66 and Sensoril.
01 Overview
Withanolides (notably withaferin A and withanolide glycosides) are thought to modulate the HPA axis and GABAergic signalling, which underpins ashwagandha's reasonably well-replicated effects on cortisol, perceived stress and sleep quality. Several small placebo-controlled trials in men also report gains in strength, muscle size and a rise in total testosterone, though effect sizes are modest, trial quality is variable, and many studies are industry-funded.
Among lifters it is taken as a daily adaptogen for recovery, sleep and a mild anabolic edge rather than as a true hormonal drug. It is generally well tolerated; the main practical concerns are drowsiness, occasional GI upset and rare reports of liver injury. It is legal and sold as a dietary supplement worldwide.
02 Mechanism
Withanolide-rich root extract that appears to dampen HPA-axis output (lowering cortisol) and enhance GABAergic tone, with proposed antioxidant and modest steroidogenic effects reported in some human and animal work.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Standardised root extract | 300–600 mg/day | Oral | Typical KSM-66 dosing (~5% withanolides), often split twice daily. |
| Higher trial dosing | 600–1000 mg/day | Oral | Upper range used in some strength/stress studies. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Reduced cortisol and perceived stressThe most consistently replicated benefit across placebo-controlled trials; improved stress and sleep scores. | cortisol -15 to -30% | Clinical | |
| Small rise in testosteroneSeveral RCTs in men report increased total testosterone, but effect sizes are small and not seen in all studies. | modest / inconsistent | Clinical | |
| Modest strength / muscle gainsSome resistance-training trials show greater gains in strength and muscle size versus placebo, though methodological quality varies. | small | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Drowsiness / sedationDaytime sedation and grogginess, reflecting the herb's calming GABAergic activity. | Mild | Common | Observational | |
| Gastrointestinal upsetNausea, loose stools or abdominal discomfort, especially at higher doses. | Mild | Common | Observational | |
| Idiosyncratic liver injuryCase reports and case series describe cholestatic/hepatocellular liver injury linked to ashwagandha supplements, usually reversible on stopping. | Severe | Rare | Observational |