Ashwagandha
Ashwagandha (Withania somnifera) is an adaptogenic herb used for stress, anxiety and sleep, and marketed to athletes for recovery and testosterone support. Its withanolides have GABA-mimetic and cortisol-lowering effects. Several randomised trials show reductions in perceived stress and cortisol, with a favourable safety profile, though rare liver injury has been reported.
01 Overview
Standardised root extracts such as KSM-66 and Sensoril have been tested in randomised trials for stress and anxiety, generally showing meaningful reductions in perceived-stress scores and serum cortisol over 6-8 weeks. Some studies also report improved sleep, and smaller trials suggest modest strength and testosterone effects in men.
Withanolides appear to act partly through GABA-mimetic activity and modulation of the stress axis. It is well tolerated overall, but there are case reports of idiosyncratic hepatotoxicity and it can stimulate thyroid function, so caution applies in liver or thyroid disease.
02 Mechanism
Withanolides exhibit GABA-mimetic activity at GABA-A receptors and modulate the hypothalamic-pituitary-adrenal axis, lowering cortisol; additional antioxidant and neuroprotective effects are described.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Stress / anxiety | 300–600 mg/day | Oral | Standardised root extract, often split into two doses over 6-8 weeks. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Reduced stress and cortisolRandomised trials show lower perceived-stress scores and serum cortisol over several weeks. | Moderate | Clinical | |
| Improved sleepSome trials report better sleep quality and reduced anxiety. | Mild-moderate | Clinical | |
| Modest strength / recovery supportSmall resistance-training studies suggest minor gains in strength and testosterone in men. | Small | Observational |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| HepatotoxicityCase reports of idiosyncratic liver injury with some extracts. | Severe | Rare | Observational | |
| GI upset and drowsinessNausea, loose stools or mild sedation, especially at higher doses. | Mild | Uncommon | Observational | |
| Thyroid stimulationMay raise thyroid hormone levels, potentially problematic in hyperthyroidism. | Moderate | Rare | Observational |