Ashwagandha Benefits and Side Effects: Complete Guide (2025)

Last updated: mayo 7, 2026
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In This Article

Ashwagandha (Withania somnifera) is one of the most researched adaptogens with over 24 randomized controlled trials. Here’s everything you need to know — benefits, side effects, extracts, and who should avoid it.

Proven Benefits (RCT Evidence)

Cortisol Reduction

-28% cortisol after 8 weeks (600mg KSM-66). Multiple RCTs confirm.

Testosterone (Men)

+15-40% testosterone in multiple RCTs. Particularly strong in stressed men.

Anxiety Reduction

Significant reduction on GAD-7 and DASS-21 scales vs placebo.

Athletic Performance

+14% VO2max improvement, increased muscle recovery in trained athletes.

Sleep Quality

Improves sleep onset, quality scores, and morning alertness (PSQI validated).

Thyroid (Limited Evidence)

Some evidence for T3/T4 improvement in subclinical hypothyroid. Monitor if on thyroid medication.

Side Effects & Who Should Avoid It

Generally Safe

  • Well tolerated at 300-600mg/day
  • No organ toxicity in 12-week trials
  • Mild GI upset in some (take with food)
  • Very rare: sedation if sensitive to adaptogens

Avoid If You Have

  • Autoimmune disease (stimulates immune system)
  • Thyroid disorders (consult doctor)
  • Hormone-sensitive cancers
  • Pregnancy (uterine stimulant)
  • On sedatives/benzodiazepines

KSM-66 vs Sensoril: Which to Choose

KSM-66 Sensoril
Plant part Root only Root + leaves
Withanolide content 5% 10%
Clinical trials 24+ RCTs 12+ RCTs
Standard dose 600mg/day 250mg/day
Best for Testosterone, performance Stress, anxiety, sleep

Top Rated Supplements

Ashwagandha KSM-669.3/10Tongkat Ali Physta8.8/10Magnesium Glycinate9.6/10

All reviews include price comparisons & third-party testing verification

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