What Is Ashwagandha and Why Is Everyone Taking It?
Withania somnifera — known as ashwagandha — is an Ayurvedic medicinal herb classified as an adaptogen: a substance claimed to help the body adapt to physical and psychological stress. It has been used in traditional Indian medicine for over 3,000 years. In 2025–2026, it became one of the fastest-growing supplement ingredients in mainstream markets, driven by cultural interest in stress management, "cortisol solutions," and the popularisation of adaptogens in social media health content.
The active compounds are primarily withanolides — a class of naturally occurring steroidal lactones found in the roots and leaves. Standardised extracts specify their withanolide percentage — the most studied brands being KSM-66 (root only, 5% withanolides) and Sensoril (root + leaf, 10% withanolides).
Cortisol & Stress — The Most Solid Evidence
The strongest and most consistently replicated evidence for ashwagandha is in the domain of stress and cortisol reduction. Multiple RCTs have found significant reductions in serum cortisol and significant improvements in self-reported stress scores in stressed adults taking standardised ashwagandha extract.
| Study | Form | Dose | Duration | Cortisol Result | Stress Score |
|---|---|---|---|---|---|
| Chandrasekhar et al. 2012 (n=64) | KSM-66 300mg 2x | 600mg/day | 8 weeks | −27.9% serum cortisol | Significant improvement |
| Pratte et al. 2014 (n=98) | KSM-66 | 300mg 2x/day | 8 weeks | −30.5% serum cortisol | PSS score improved |
| Lopresti et al. 2019 (n=60) | Sensoril | 120mg/day | 8 weeks | Significant but smaller | Significant improvement |
| Auddy et al. 2008 (n=130) | Sensoril | 125–500mg/day | 8 weeks | Dose-dependent reduction | Significant |
Testosterone Claims — More Complicated
Ashwagandha is frequently marketed for testosterone support. The evidence is more limited and more nuanced than the marketing implies. Several studies in healthy men under physical or psychological stress have shown modest increases in testosterone with ashwagandha supplementation — but the effect appears primarily linked to stress-mediated cortisol reduction rather than a direct androgenic mechanism.
In men with normal testosterone levels who are not under significant stress, the testosterone-raising effect is small and inconsistent across studies. The mechanism: chronically elevated cortisol (via HPA axis activation) suppresses luteinising hormone (LH) and reduces testosterone production. Reducing cortisol through ashwagandha can partially reverse this suppression — in stressed men specifically. This is not the same as a direct testosterone booster.
Sleep Quality Research
A 2019 RCT (Langade et al.) in 60 participants with insomnia found KSM-66 at 300mg twice daily for 10 weeks produced significant improvements in sleep quality (Pittsburgh Sleep Quality Index), sleep onset latency, total sleep time, and sleep efficiency. This is one of the cleanest studies in the ashwagandha literature — a dedicated sleep-quality endpoint with validated measurement tools. The effect appears to be mediated through GABA receptor activity of certain withanolides, which produces mild anxiolytic and sleep-promoting effects.
Practical implication: if you take ashwagandha primarily for sleep, evening dosing (one dose 30–60 minutes before bed) is more logical than morning dosing.
Muscle & Strength Data — Emerging but Real
Several RCTs have examined ashwagandha's impact on resistance training outcomes in young, healthy men. A 2015 RCT (Wankhede et al.) in 57 young men found KSM-66 at 300mg twice daily for 8 weeks, combined with resistance training, produced significantly greater gains in muscle strength (bench press, leg extension) and muscle size compared to placebo. The testosterone mechanism is one proposed pathway; reduced exercise-induced cortisol (which is catabolic) is another.
These are promising findings, but the effect sizes are modest relative to creatine (which has 500+ studies). Ashwagandha is best viewed as a complementary ingredient that may marginally enhance recovery and reduce training-induced cortisol — not a primary muscle-building supplement.
KSM-66 vs Sensoril vs Generic Root Powder
| Form | Withanolides | Part Used | Evidence Base | Effective Dose |
|---|---|---|---|---|
| KSM-66 | ≥5% | Root only | 10+ RCTs — extensive | 300–600mg/day |
| Sensoril | ≥10% | Root + leaf | 5+ RCTs — solid | 125–500mg/day |
| Generic Root Extract | Varies (2–5%) | Root | Limited specific data | 500–1,000mg/day |
| Generic Root Powder | Unknown — low | Whole root | Cannot translate trial data | Avoid for clinical use |
Dosing, Timing, and Who Benefits Most
- Dose: 300–600mg/day of KSM-66 or 125–250mg/day of Sensoril. Take with food to minimise GI discomfort in sensitive individuals.
- Timing: Twice-daily dosing (morning and evening) is most common in clinical trials. For sleep specifically, an evening dose is preferable. For stress management, morning and evening split.
- Time to effect: Most RCTs show meaningful effects at 8–12 weeks. Don't judge effectiveness at 2–3 weeks.
- Who benefits most: Chronically stressed adults, shift workers, people with elevated baseline cortisol, athletes with poor recovery, and anyone with sleep-onset difficulty.
- Who may not need it: People with normal cortisol levels and effective stress management — ashwagandha's effects appear most pronounced when baseline stress hormones are elevated.