Ashwagandha

Ashwagandha is a rasayana, one of the rejuvenative drugs given not for a named complaint but to restore the body’s capacity generally. It is classified as bitter and astringent in taste and heating in potency. It reduces kapha and vata and increases pitta, and the part used is the root.

It is placed in three overlapping categories:

• Balya — strength-giving. The root is prescribed for wasting, convalescence, low body weight in children, and the depletion that follows long illness or overwork.
• Vajikarana — the aphrodisiac and reproductive category. It is given for low libido, male infertility and sexual debility.
• Medhya — intellect-promoting, at the calming end of that group rather than the stimulating one.

Ayurvedic practice also uses it for emaciation, impotence, bronchitis, insomnia, leukoderma, lumbago, arthritis and rheumatism, to promote conception and for premature ageing. It has been given as a nutrient to pregnant women ^{31,32Reference 31Bone K · 2013Principles and Practice of PhytotherapyReference 32Bone · 2003A Clinical Guide to Blending Liquid Herbs: Herbal Formulations for the Individual Patient}.

The name ashwa-gandha means “smell of a horse”, read both as a description of the fresh root’s odour and as a reference to the strength it is meant to confer.

The classical preparation is the powdered root taken with warm milk, often with honey or ghee. This is still how it is most often taken in India today.

Unani practice on the Indian subcontinent uses the root as asgand, classified as hot and dry. It is used as a restorative and nerve tonic, for general debility and wasting, and as an aphrodisiac.

Multiple randomised, double-blind, placebo-controlled trials report reductions in perceived stress and anxiety alongside lower serum cortisol.

In 64 adults with chronic stress, 300 mg of a full-spectrum root extract twice daily for 60 days lowered scores on every stress scale and lowered serum cortisol significantly compared with placebo ^{5Reference 5Chandrasekhar K et al. · 2012RCTA prospective, randomised double-blind, placebo-controlled study of a high-concentration full-spectrum ashwagandha root extract in reducing stress and anxiety — RCTView study →}.

In 60 stressed adults, 240 mg of the Shoden extract once daily for 60 days reduced Hamilton Anxiety (HAM-A) scores and morning cortisol compared with placebo ^{4Reference 4Lopresti AL et al. · 2019RCTStress-relieving and pharmacological actions of an ashwagandha extract — a randomised, double-blind, placebo-controlled studyView study →}.

A dose-response trial in 60 stressed adults found lower stress scores and cortisol at both 250 mg and 600 mg a day, with the stronger result at 600 mg ^{6Reference 6Salve J et al. · 2019RCTAdaptogenic and anxiolytic effects of ashwagandha root extract in healthy adults — a double-blind, randomised, placebo-controlled clinical studyView study →}.

Meta-analyses agree on the direction. One pooled 12 RCTs with 1,002 participants and found significant reductions in anxiety and stress, though it rated the certainty of the evidence as low ^{1Reference 1Akhgarjand C et al. · 2022Meta-analysisDoes Ashwagandha supplementation have a beneficial effect on the management of anxiety and stress? — systematic review and meta-analysis of randomised controlled trialsView study →}. A 2024 synthesis of 9 RCTs (558 participants) reported lower Perceived Stress Scale, Hamilton Anxiety and serum cortisol scores than placebo ^{2Reference 2Arumugam V et al. · 2024Meta-analysisEffects of Ashwagandha (Withania somnifera) on stress and anxiety — systematic review and meta-analysisView study →}. A second 2024 review pooled five RCTs and found lower HAM-A scores ^{3Reference 3Fatima K et al. · 2024Meta-analysisSafety and efficacy of Withania somnifera for anxiety and insomnia — systematic review and meta-analysisView study →}.

An earlier trial tested a package of naturopathic care that included ashwagandha (300 mg twice daily) alongside diet advice, breathing exercises and a multivitamin. It reduced anxiety more than psychotherapy did ^{30Reference 30Cooley K et al. · 2009RCTNaturopathic care for anxiety — a randomised controlled trial (ISRCTN78958974)View study →}.

Effect sizes vary widely between trials, the trials are small and short, and almost all use one of a handful of standardised extracts rather than a traditional preparation ^{1,3Reference 1Akhgarjand C et al. · 2022Meta-analysisDoes Ashwagandha supplementation have a beneficial effect on the management of anxiety and stress? — systematic review and meta-analysis of randomised controlled trialsView study →Reference 3Fatima K et al. · 2024Meta-analysisSafety and efficacy of Withania somnifera for anxiety and insomnia — systematic review and meta-analysisView study →}.

Gap: No head-to-head trial against first-line anxiolytics, and no data beyond about 12 weeks.

A 2021 systematic review and meta-analysis of five RCTs (400 participants) found a small but significant improvement in overall sleep. The effect was clearer in adults diagnosed with insomnia, at doses of 600 mg a day or more, and over eight weeks or longer ^{7Reference 7Cheah KL et al. · 2021Meta-analysisEffect of ashwagandha (Withania somnifera) extract on sleep — a systematic review and meta-analysisView study →}.

A 10-week trial in 60 patients with insomnia and anxiety, using actigraphy, found shorter sleep-onset latency and better sleep efficiency with 300 mg twice daily than with placebo ^{9Reference 9Langade D et al. · 2019RCTEfficacy and safety of ashwagandha root extract in insomnia and anxiety — a double-blind, randomised, placebo-controlled studyView study →}.

An 8-week trial in 80 people, half healthy and half with insomnia, improved sleep parameters and Pittsburgh Sleep Quality Index scores in both groups, with larger gains in the insomnia group ^{8Reference 8Langade D et al. · 2021RCTClinical evaluation of ashwagandha root extract on sleep in healthy volunteers and insomnia patients — a double-blind, randomised, placebo-controlled studyView study →}.

Effects on sleep are modest and tied to standardised root extracts.

Gap: Small pooled sample, subjective sleep measures dominate over polysomnography, and no long-term or dependence/withdrawal data.

In 46 men with low sperm counts, 90 days of a full-spectrum root extract (675 mg a day in three doses) raised sperm count by 167%, semen volume by 53% and motility by 57% from baseline, with minimal change on placebo ^{11Reference 11Ambiye VR et al. · 2013RCTClinical evaluation of the spermatogenic activity of ashwagandha root extract in oligospermic males — a pilot randomised studyView study →}.

Testosterone rose as a secondary outcome in a resistance-training trial: by 96 ng/dL on ashwagandha against 18 ng/dL on placebo ^{10Reference 10Wankhede S et al. · 2015RCTExamining the effect of Withania somnifera supplementation on muscle strength and recovery — a randomised controlled trialView study →}. In stressed adults, testosterone rose in men taking ashwagandha, but the change did not differ significantly from placebo ^{4Reference 4Lopresti AL et al. · 2019RCTStress-relieving and pharmacological actions of an ashwagandha extract — a randomised, double-blind, placebo-controlled studyView study →}.

Samples are small and populations are selected (sub-fertile men), and the effect in men with normal hormone levels is far less clear.

Gap: No fertility (pregnancy/live-birth) endpoints, small selected samples, and little evidence of a testosterone effect in men with normal baseline levels.

An 8-week randomised, double-blind, placebo-controlled trial in 57 young men new to resistance training gave 300 mg of root extract twice daily alongside training. Compared with placebo, it produced greater gains in bench-press and leg-extension strength, larger arm and chest muscle size, greater fat loss and lower creatine kinase after exercise ^{10Reference 10Wankhede S et al. · 2015RCTExamining the effect of Withania somnifera supplementation on muscle strength and recovery — a randomised controlled trialView study →}.

A 2026 meta-analysis of 13 trials (599 participants) found a moderate overall improvement in exercise performance. The effect was most consistent for aerobic endurance; strength effects were positive but uncertain, and results varied between trials ^{38Reference 38Li X et al. · 2026Meta-analysisEffects of Withania somnifera (ashwagandha) supplementation on exercise performance — a systematic review and three-level meta-analysisView study →}.

An 8-week trial in 50 adults with mild cognitive impairment (300 mg root extract twice daily) improved immediate and general memory on Wechsler Memory Scale subtests, along with executive function, attention and processing speed ^{12Reference 12Choudhary D et al. · 2017RCTEfficacy and safety of ashwagandha root extract in improving memory and cognitive functions — RCT in mild cognitive impairmentView study →}.

A 14-day crossover trial in 20 healthy men, using an aqueous extract of roots and leaves, improved reaction times on several computerised tests ^{13Reference 13Pingali U et al. · 2014RCTEffect of standardised aqueous extract of Withania somnifera on cognitive and psychomotor performance in healthy participants — randomised trialView study →}.

Both are pilot-scale, short, and use different extracts, so replication is thin.

An 8-week RCT in 50 adults with subclinical hypothyroidism (600 mg a day of root extract) lowered TSH and raised T3 and T4 compared with placebo ^{14Reference 14Sharma AK et al. · 2018RCTEfficacy and safety of ashwagandha root extract in subclinical hypothyroid patients — a double-blind, randomised placebo-controlled trialView study →}. A thyroid substudy within a bipolar-disorder trial found T4 rises in all three ashwagandha-treated patients who had abnormal thyroid tests ^{15Reference 15Gannon JM et al. · 2014RCTSubtle changes in thyroid indices during a placebo-controlled study of an extract of Withania somnifera in persons with bipolar disorderView study →}.

The direction is consistently thyroid-stimulating. Case reports describe ashwagandha causing thyrotoxicosis, including painless thyroiditis, that resolved on stopping ^{29,36Reference 29van der Hooft CS et al. · 2005Case reportThyrotoxicosis following the use of ashwagandha — case reportView study →Reference 36Hayashi M et al. · 2024Case reportPainless thyroiditis by Withania somnifera (ashwagandha) — case reportView study →}.

The effect may be useful in an underactive thyroid and harmful in an overactive or already-treated one.

Gap: One small efficacy RCT, no data on overt hypothyroidism, and case reports of over-stimulation.

The anti-inflammatory work is preclinical. Withaferin A inhibited Helicobacter pylori-induced IL-1β production in mouse dendritic cells by regulating NF-κB and NLRP3 inflammasome activation ^{23Reference 23Kim JE et al. · 2015In vitroWithaferin A inhibits Helicobacter pylori-induced production of IL-1β in dendritic cells by regulating NF-κB and NLRP3 inflammasome activation — in vitroView study →}.

In a mouse model of fulminant hepatitis it reduced liver injury by acting on macrophages, partly through NLRP3 ^{26Reference 26Xia Y et al. · 2021AnimalWithaferin A alleviates fulminant hepatitis by targeting macrophage and NLRP3 — mouse in vivoView study →}.

This work uses purified withaferin A at doses unrelated to oral dosing, and there is no human anti-inflammatory trial.

Gap: No human anti-inflammatory endpoint.

A single 8-week pilot RCT in 50 healthy women (300 mg of a high-concentration root extract twice daily) reported significant improvement over placebo in Female Sexual Function Index total, arousal, lubrication, orgasm and satisfaction scores, plus more successful sexual encounters ^{16Reference 16Dongre S et al. · 2015RCTEfficacy and safety of ashwagandha root extract in improving sexual function in women — a pilot randomised controlled trialView study →}. It is one small study using subjective psychometric scales.

A 2020 systematic review and meta-analysis found that W. somnifera lowered blood glucose, HbA1c, insulin and lipid markers. The pooled evidence came mostly from 6 in-vitro and 13 preclinical studies, against 5 clinical studies, and the authors concluded that the clinical data were not robust enough to support its use in diabetes ^{17Reference 17Durg S et al. · 2020Meta-analysisWithania somnifera (Indian ginseng) in diabetes mellitus — a systematic review and meta-analysisView study →}.

Gap: Human evidence is sparse and largely uncontrolled; the meta-analytic effect is carried by animal and cell data.

Withaferin A and related withanolides show anticancer activity in cells and animals.

Withanolides suppressed NF-κB activation, enhancing apoptosis and inhibiting invasion and osteoclastogenesis in cell lines ^{19Reference 19Ichikawa H et al. · 2006In vitroWithanolides potentiate apoptosis, inhibit invasion and abolish osteoclastogenesis through suppression of NF-κB — in vitroView study →}. Withaferin A inhibited the chaperone HSP90 in pancreatic cancer cells and slowed the growth of pancreatic tumour xenografts in mice ^{20Reference 20Yu Y et al. · 2010In vitroWithaferin A targets heat-shock protein 90 in pancreatic cancer cells — in vitroView study →}. It is also a potent inhibitor of angiogenesis ^{22Reference 22Mohan R et al. · 2004In vitroWithaferin A is a potent inhibitor of angiogenesis — in vitro/animal modelView study →}.

A root extract made with dimethyl sulfoxide was cytotoxic to human T-leukaemia cells, and also showed genotoxic potential in the same experiments ^{21Reference 21Turrini E et al. · 2016In vitroWithania somnifera induces cytotoxic and cytostatic effects on human T-leukaemia cells — in vitroView study →}. The in-vivo withaferin A work is reviewed in ^{18Reference 18Vyas AR · 2014ReviewMolecular targets and mechanisms of cancer prevention and treatment by withaferin A — reviewView study →}.

In humans, a review of clinical studies lists one trial of the root as a chemotherapy adjunct for fatigue and quality of life ^{28Reference 28Tandon N · 2020Systematic reviewSafety and clinical effectiveness of Withania somnifera root in human ailments — systematic reviewView study →}.

Gap: No human anticancer efficacy data; the anticancer work uses purified compounds or solvent extracts in cells and rodents.

Tolerability. In short-term trials, side effects are mild and mostly drowsiness, stomach discomfort or loose stools ^{28Reference 28Tandon N · 2020Systematic reviewSafety and clinical effectiveness of Withania somnifera root in human ailments — systematic reviewView study →}. An 8-week safety trial in 80 healthy adults taking 300 mg twice daily found no changes in blood counts, liver or kidney tests, or thyroid hormones, and no adverse events ^{27Reference 27Verma N et al. · 2021RCTSafety of ashwagandha root extract — a randomised, placebo-controlled study in healthy volunteersView study →}.

Liver. Ashwagandha is a recognised cause of herb-induced liver injury. A case series from Iceland and the US Drug-Induced Liver Injury Network described five people who developed jaundice, itching and nausea 2–12 weeks after starting it. The injury was cholestatic or mixed, and liver tests returned to normal within 1–5 months ^{24Reference 24Björnsson HK et al. · 2020Case reportAshwagandha-induced liver injury — a case series from Iceland and the US Drug-Induced Liver Injury NetworkView study →}. Later reports include hepatocellular injury, and one reported case ended in liver transplantation ^{25Reference 25Bokan G et al. · 2023Herb-induced liver injury by Ayurvedic ashwagandha as assessed for causality by the updated RUCAM — an emerging causeView study →}.

Thyroid. Ashwagandha raises thyroid hormone levels. Case reports describe thyrotoxicosis and painless thyroiditis that resolved when it was stopped ^{29,36Reference 29van der Hooft CS et al. · 2005Case reportThyrotoxicosis following the use of ashwagandha — case reportView study →Reference 36Hayashi M et al. · 2024Case reportPainless thyroiditis by Withania somnifera (ashwagandha) — case reportView study →}. This matters for anyone with an overactive thyroid or already taking thyroid hormone.

Medicines. A systematic review found no inhibition of the drug-metabolising enzymes CYP3A4 or CYP2D6 in laboratory or animal studies ^{28Reference 28Tandon N · 2020Systematic reviewSafety and clinical effectiveness of Withania somnifera root in human ailments — systematic reviewView study →}. In laboratory tests, ashwagandha root extracts raised the expression of CYP3A4 in human liver cells, an effect that has not been tested in people ^{42Reference 42Kumar S et al. · 2021In vitroInvestigation of CYP2B6, 3A4 and β-esterase interactions of Withania somnifera (L.) Dunal in human liver microsomes and HepG2 cells — in vitroView study →}.

Because it is thyroid-active and mildly sedating, caution is still sensible alongside thyroid medication, sedatives and immunosuppressants. No human drug-interaction trials have been done.

Quality. Lead contamination has been reported in some Indian-sourced material, so tested or certified products are preferable.