Ashwagandha: How This Adaptogen Lowers Cortisol
Ashwagandha is one of the most-studied herbal supplements on earth. Here's the science of how it calms cortisol — and when not to take it.
Ashwagandha (Withania somnifera) is a root that's been used in Ayurvedic medicine for over 3,000 years. Modern research has caught up: it's now one of the most-studied adaptogens, with strong evidence for reducing stress, anxiety, and cortisol levels.
What's an adaptogen?
Adaptogens are plants that help your body resist physical, chemical, and biological stress. They don't sedate you — they help your nervous system adapt. Ashwagandha is one of the few adaptogens with rigorous clinical evidence behind it.
How ashwagandha works
It modulates the hypothalamic-pituitary-adrenal (HPA) axis — the system that controls your stress response. Specifically:
- Lowers chronically elevated cortisol
- Reduces inflammatory markers
- Supports GABA receptor function (calming)
- Modulates serotonin signalling
The evidence
Multiple double-blind RCTs show:
- 28% reduction in cortisol with 600 mg KSM-66 daily for 60 days
- Significant reductions in stress and anxiety scores (PSS, HAM-A)
- Improved sleep onset and quality
- Better DHEA-S levels (a youth hormone) in stressed adults
Dose and form
Look for KSM-66 or Sensoril — standardised root extracts with documented active compound levels (withanolides). Avoid generic 'ashwagandha root powder' which is much weaker.
Dose: 300–600 mg KSM-66 once daily, ideally in the evening. Effects build over 4–8 weeks.
Who should NOT take ashwagandha
- Pregnancy or nursing — not enough safety data
- Hyperthyroid — may further elevate thyroid hormones
- Autoimmune conditions — can stimulate immune activity
- On sedatives or thyroid meds — talk to your prescriber first
Adaptogens are powerful. Their gentleness is in how they work, not how strong they are.
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