Plain Language Summary

Ashwagandha is an adaptogenic herb with the strongest clinical evidence for reducing perceived stress, lowering cortisol, and improving sleep quality. Human trials also show benefits for strength, recovery, and thyroid function in subclinical hypothyroidism. Overall evidence is moderate to strong for stress-related endpoints.

What It Is

Ashwagandha (Withania somnifera) is a root used in Ayurvedic medicine for over 3,000 years. Also called Indian ginseng or winter cherry. The root contains withanolides, alkaloids, and saponins believed to be responsible for its biological effects.

Traditional Uses

  • Stress and fatigue
  • Low energy
  • Immune support
  • Male reproductive health
  • Thyroid support

Mechanism of Action

Withanolides modulate the HPA (hypothalamic-pituitary-adrenal) axis, reducing cortisol output under stress. Also shows activity at GABA receptors, which may explain anxiolytic effects. Anti-inflammatory pathways including NF-kB inhibition have been demonstrated in preclinical models.

Human Research Highlights

  • Multiple RCTs show significant reductions in perceived stress and anxiety scores vs. placebo over 8-12 weeks.
  • KSM-66 and Sensoril ashwagandha extracts show the most consistent clinical evidence.
  • Studies show morning cortisol reductions of 14-30% in stressed adults.
  • Two RCTs show improved sleep quality, including reduced sleep onset latency and improved sleep efficiency.
  • Several trials demonstrate increased muscular strength and recovery in resistance-trained adults.
  • A small RCT found significant improvement in subclinical hypothyroidism markers including TSH and T4.

Preclinical & Laboratory Research

  • In vitro studies show anticancer activity, not yet replicated in human trials.
  • Animal models demonstrate neuroprotective effects relevant to cognitive aging.
  • Preclinical data supports anti-inflammatory and immunomodulatory effects.

Dosage Studied

300-600 mg standardized extract (KSM-66 or Sensoril) daily, typically in divided doses. Full-spectrum root powder studied at 1-5 g daily.

Safety Notes

  • Generally well-tolerated at standard doses (300-600 mg extract daily).
  • Rare cases of liver injury reported, likely related to specific adulterated products.
  • May lower thyroid stimulating hormone - monitor if on thyroid medication.
  • May enhance sedative effects of benzodiazepines and other sedatives.
  • Avoid in pregnancy due to potential uterine-stimulating effects.
  • Discontinue 2 weeks before scheduled surgery due to CNS depressant potential.

Drug Interactions

  • Thyroid medications (levothyroxine): may require dose adjustment
  • Sedatives and benzodiazepines: additive CNS depressant effect
  • Immunosuppressants: may counteract immunosuppressive effects

Research Gaps

  • Long-term safety beyond 12 weeks not well studied in clinical trials.
  • Optimal dose range not established by head-to-head comparison.
  • Limited evidence for cognitive benefits in non-stressed populations.
  • Cancer applications remain preclinical only.

Clinical Relevance

Ashwagandha is one of the best-evidenced adaptogens for stress and cortisol reduction. Reasonable first-line adaptogen choice for stressed adults with sleep disruption. Athletes may benefit for recovery. Those with autoimmune thyroid conditions should use with medical supervision.

Citations

  1. Chandrasekhar K et al. A prospective, randomized double-blind, placebo-controlled study of safety and efficacy of a high-concentration full-spectrum extract of ashwagandha root. Indian J Psychol Med. 2012.
  2. Langade D et al. Efficacy and Safety of Ashwagandha Root Extract in Insomnia and Anxiety. Medicine. 2019.
  3. Wankhede S et al. Examining the effect of Withania somnifera supplementation on muscle strength and recovery. J Int Soc Sports Nutr. 2015.

Disclaimer: Educational information only. Not medical advice. Consult a qualified healthcare professional before use.

Last updated: March 1, 2025