Ashwagandha: Clinical Evidence & Substantiation Summary
What Is Ashwagandha?
Ashwagandha (Withania somnifera) is an adaptogenic herb with a long history of use in Ayurvedic medicine. It has become one of the most studied botanical ingredients in dietary supplements, with a growing body of clinical evidence supporting its effects on stress, anxiety, sleep, and physical performance.
Mechanism of action: Ashwagandha's bioactive compounds — withanolides — modulate the hypothalamic-pituitary-adrenal (HPA) axis, reducing cortisol output. It also exhibits GABAergic activity and has been shown to influence serotonin pathways, contributing to its anxiolytic and sleep-promoting effects.
Clinical Evidence Summary
Below are 5 key clinical studies on Ashwagandha. Nutra Comp analyses 34+ studies in its full clinical evidence report.
A prospective, randomized double-blind, placebo-controlled study of safety and efficacy of a high-concentration full-spectrum extract of ashwagandha root in reducing stress and anxiety in adults
Population: 64 adults with chronic stress
Key finding: Significant reduction in serum cortisol (p<0.0001) and perceived stress scores (PSS) vs. placebo after 60 days at 300 mg twice daily.
Adaptogenic and Anxiolytic Effects of Ashwagandha Root Extract in Healthy Adults: A Double-Blind, Randomized, Placebo-Controlled Clinical Study
Population: 58 healthy adults
Key finding: Significant improvements in perceived stress (p=0.001), sleep quality (p<0.001), and serum cortisol (p=0.002) compared with placebo at 240 mg/day.
Effects of Ashwagandha (Withania somnifera) on VO2max: A Systematic Review and Meta-Analysis
Population: 5 RCTs, 198 participants
Key finding: Ashwagandha supplementation significantly increased VO2max in healthy adults and athletes (pooled effect: +2.89 ml/kg/min, p<0.01).
Examining the effect of Withania somnifera supplementation on muscle strength and recovery: a randomized controlled trial
Population: 57 young male subjects (resistance training)
Key finding: Significantly greater increases in muscle strength (bench press: p<0.001, leg extension: p<0.001) and muscle size with 300 mg twice daily.
Efficacy and Safety of Ashwagandha Root Extract on Cognitive Functions in Healthy, Stressed Adults
Population: 50 healthy adults under stress
Key finding: Significant improvements in immediate and general memory (p<0.001), attention, and information processing speed at 300 mg twice daily for 8 weeks.
Evidence-Based Structure–Function Claims
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Frequently Asked Questions
Is ashwagandha FDA approved?
Ashwagandha is not FDA-approved as a drug. As a dietary supplement ingredient, it does not require FDA approval before sale. However, any claims made about ashwagandha supplements must comply with DSHEA regulations and be limited to structure–function claims that are truthful, non-misleading, and substantiated.
What are the most studied benefits of ashwagandha?
The most robust clinical evidence for ashwagandha centres on stress and anxiety reduction (measured by cortisol levels and validated stress scales), sleep quality improvement, and physical performance enhancement (VO2max and muscle strength). Evidence for cognitive benefits is emerging but less extensive.
What dosage of ashwagandha is used in clinical studies?
Most clinical trials use between 300–600 mg/day of standardised root extract (typically KSM-66 or Sensoril), often divided into two doses. Some studies use up to 1,000 mg/day.
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