Ashwagandha

Ashwagandha (Withania somnifera) is a shrub native to India, North Africa, and the Mediterranean region whose root and berry have been used in Ayurvedic medicine for over 3,000 years, primarily as a rasayana (rejuvenating) herb — a category of preparations traditionally intended to promote physical endurance, vitality, and longevity. The name derives from Sanskrit: ashwa (horse) and gandha (smell), referring to the root's characteristic horse-like odor and the traditional belief that consuming it could confer the strength and stamina of a horse.¹

The primary bioactive compounds in ashwagandha are steroidal lactones called withanolides, concentrated in the root. Commercial extracts are typically standardized to withanolide content (commonly 2.5% to 10% withanolides). The root is available as a whole dried root powder, a water-extracted or hydro-alcoholic extract, or a root plus leaf combination. Extract forms are used in most clinical research because of more consistent withanolide content.¹

The NIH ODS notes that ashwagandha has been studied most extensively for stress and anxiety reduction, sleep quality improvement, and athletic performance enhancement.

For stress and anxiety: A 2021 systematic review identified multiple small randomized controlled trials using ashwagandha root extract that found statistically significant reductions in perceived stress and anxiety scores, along with reductions in cortisol levels, compared to placebo — typically at doses of 300–600 mg of root extract daily for 8–12 weeks. The trials were generally of short duration and limited sample size. The ODS concludes that ashwagandha may be helpful for reducing stress, but notes that the evidence base is still developing.¹

For sleep quality: A small number of randomized controlled trials have found that ashwagandha improved sleep quality measures, sleep onset latency, and morning alertness in adults with sleep-related complaints at similar doses and durations to the stress trials. Evidence quality is described as limited but promising.¹

For athletic performance: Several small trials have investigated ashwagandha's effects on muscular strength, power, recovery, and aerobic capacity in healthy adults and athletes. Results have generally favored ashwagandha over placebo on strength and power outcomes, but studies are small and heterogeneous in design, and the ODS characterizes the evidence as limited.¹

Most clinical trials supporting efficacy for stress, sleep, or performance outcomes have used 300–600 mg per day of a root extract, administered as a single dose or split into two doses, for periods of 8–12 weeks. Some protocols use up to 1,000 mg daily. Higher doses (2,000–3,000 mg) in older small studies were associated with more GI side effects. No Tolerable Upper Intake Level has been established.¹

Whole root powder and aqueous extracts may require higher doses to achieve the withanolide concentrations used in standardized extract studies.

Oral, as capsules, tablets, powder, or liquid extract.

Standard storage at room temperature, away from heat and moisture.

Ashwagandha is generally considered safe at typical supplement doses for periods up to 3 months in most clinical trials. The most common side effects are gastrointestinal — nausea, diarrhea, and stomach upset — particularly at higher doses.¹

Several considerations require attention:¹

• Liver injury: A small number of case reports have linked ashwagandha supplementation to drug-induced liver injury (DILI), including some serious cases. The NIH's LiverTox database includes ashwagandha as a supplement with evidence of hepatotoxicity risk. While uncommon, this risk should be acknowledged. Individuals with pre-existing liver conditions or those taking hepatotoxic medications should exercise caution.
• Thyroid effects: Ashwagandha may increase thyroid hormone levels (T3 and T4) in some individuals by stimulating thyroid function. Individuals with thyroid disease, or those taking thyroid medications, should monitor thyroid function if using ashwagandha and consult their clinician.
• Blood pressure: Ashwagandha may lower blood pressure modestly; relevant consideration in individuals on antihypertensive medications.
• Blood glucose: Some studies have observed modest reductions in blood glucose; relevant in individuals on diabetes medications.
• Pregnancy and lactation: Traditionally, high doses of ashwagandha have been associated with uterine contractions and potential abortifacient properties. Ashwagandha supplements should be avoided during pregnancy. Safety during breastfeeding is insufficiently characterized.
• Sedative interactions: Ashwagandha may have mild sedating properties; additive effects with alcohol, benzodiazepines, and other CNS depressants are theoretically possible.
• Long-term use: Safety data beyond 3 months of continuous supplementation are limited.