The most robust evidence is for stress reduction. A landmark study using KSM-66 ashwagandha extract showed a 27.9% reduction in serum cortisol levels compared to placebo over 60 days. Participants also reported significant reductions in perceived stress, anxiety, and insomnia. These aren't marginal effects — they're clinically meaningful.
For testosterone, a study in the American Journal of Men's Health found that 600mg of ashwagandha root extract increased testosterone by 14.7% and DHEA-S by 18.2% in healthy men over 8 weeks. Fertility studies show significant improvements in sperm count, motility, and quality. For women, ashwagandha improves sexual function without affecting hormones negatively.
Ashwagandha's primary active compounds — withanolides — modulate the HPA (hypothalamic-pituitary-adrenal) axis, which controls your stress response. By calming this axis, ashwagandha reduces cortisol output and helps your body return to baseline faster after stress. It also has GABAergic effects, promoting calm without sedation.
Beyond stress, ashwagandha has anti-inflammatory and antioxidant properties. It inhibits NF-kB (a master inflammatory switch), reduces C-reactive protein, and scavenges free radicals. There's also emerging evidence for neuroprotective effects — it promotes nerve growth factor (NGF) production and may help with memory and cognitive function.
Use a standardised root extract — KSM-66 or Sensoril are the most studied brands. Dose: 300-600mg daily. For stress and cortisol reduction, take it in the evening. For physical performance and testosterone, morning dosing works well. It can be taken with or without food.
Most people notice effects within 2-4 weeks, with maximum benefits at 8-12 weeks. Ashwagandha is generally safe, but it can interact with thyroid medications (it may increase thyroid hormone levels), immunosuppressants, and sedatives. People with autoimmune conditions should consult their doctor, as it can stimulate immune activity. Cycle it — 8 weeks on, 2-4 weeks off — to maintain sensitivity.
Anyone interested in evidence-based longevity strategies, health optimisation, and understanding the latest research on ageing and healthspan.
You are pregnant, breastfeeding, taking prescription medications, or have a pre-existing medical condition. This content is educational and does not replace professional medical advice.
Join thousands getting science-backed health tips every week.