Withania somnifera — ashwagandha — has been used in Ayurveda for over 3,000 years as a Rasayana (rejuvenating tonic). Its name translates as 'smell of horse', referring both to its odour and its reputation for imparting the strength and vitality of a horse.
Active Compounds: Withanolides
The primary bioactive compounds are withanolides, a class of steroidal lactones. The most studied is Withaferin A. These compounds inhibit NF-κB (the master inflammation switch), modulate cortisol via the HPA axis, and have demonstrated neuroplasticity-enhancing effects.
Clinical Evidence
A 2019 RCT in Medicine found 240mg/day of ashwagandha extract for 60 days reduced cortisol by 23%, reduced anxiety by 41%, and improved sleep quality significantly compared to placebo. Effects are dose-dependent up to ~600mg/day of a standardised extract.
Practical Use
Take 300–600mg of a KSM-66 or Sensoril standardised extract (minimum 5% withanolides) in the evening with fat for best absorption. Cyclical use (8 weeks on, 4 weeks off) is recommended to prevent tolerance. Avoid in thyroid conditions without physician guidance.