Ashwagandha's Research History, From Ayurveda to KSM-66
Ashwagandha has a long Ayurvedic record as a tonic root, and its human trials on root extracts measured stress scales, cortisol, strength and endurance. Two 2025 papers disagree on safety, and this page covers both, along with what the sources do not settle.
The history of ashwagandha starts in Ayurveda, where the root was valued as a tonic, and it runs through a small set of human trials on root extracts. Two 2025 papers now disagree about its safety, and that disagreement is where the modern record gets interesting. A 2011 overview in the *African Journal of Traditional, Complementary, and Alternative Medicines* describes *Withania somnifera* as a revered herb of the Indian Ayurvedic system, used as a rasayana, or tonic. The overview lists far more uses than stress, which is a reason to read it as a record of tradition rather than as evidence. ([Singh et al., 2011](https://doi.org/10.4314/ajtcam.v8i5S.9)) The 2025 record is split. A review in *Phytotherapy Research* says ashwagandha poses significant risks to pregnant women and to people with thyroid disorders, and it recommends restricting use as a food additive. A rat study published the same year found no reproductive or developmental toxicity at doses up to 2,000 mg per kilogram of body weight per day. ([Li et al., 2025](https://doi.org/10.1002/ptr.70157); [Kalaiselvan et al., 2025](https://doi.org/10.3389/fphar.2025.1572025)) ## What the human trials measured The 2012 stress trial enrolled 64 adults with a history of chronic stress. They took a 300 mg capsule of a high-concentration, full-spectrum root extract twice a day for 60 days, or placebo. On day 60, scores on every stress scale improved more on the extract, and serum cortisol fell more as well. Adverse effects were mild and comparable across groups. The abstract names no brand and no sponsor. ([Chandrasekhar et al., 2012](https://doi.org/10.4103/0253-7176.106022)) The one trial in this run that names KSM-66 is a 2015 study of 50 healthy athletic adults. Over 12 weeks, the change in VO2 max was 5.67 on KSM-66 against 1.86 on placebo, and quality-of-life subdomains improved more on the extract. The arms held 24 people on KSM-66 and 25 on placebo, and the abstract names no sponsor. ([Choudhary et al., 2015](https://doi.org/10.4103/0974-8520.169002)) Maximum Male, a men's formula, lists 300 mg of KSM-66 ashwagandha per two-tablet serving, which works out to 30 servings in a 60-tablet bottle. The label is on the [product page](https://mtangelvitamins.com/products/maximum-male-vital-energy?utm_source=learn_hub&utm_medium=content&utm_campaign=blog_post&utm_content=history-of-ashwagandha-from-ayurveda-to-ksm-66). The 2015 strength trial enrolled 57 young men with little resistance-training experience. They took 300 mg of root extract twice a day for eight weeks, or starch placebo, while both groups followed the same training program. Bench-press strength rose 46.0 kg on the extract and 26.4 kg on placebo. Testosterone rose 96.2 ng/dL on the extract and 18.0 on placebo, a difference the authors reported as significant. The abstract does not name the extract or a sponsor. ([Wankhede et al., 2015](https://doi.org/10.1186/s12970-015-0104-9)) Taken together, the three trials run from 60 days to 12 weeks, the largest enrolled 64 people, and each measured a biomarker or a performance outcome rather than a health outcome. The stress and strength trials both used 300 mg twice a day, or 600 mg a day in total, which is worth remembering when a label lists 300 mg per serving. ## What the safety record says, and where it disagrees The review's advice is specific. It names pregnant women, people with thyroid disorders, and people with liver or kidney dysfunction as groups at risk, and it reports multiple cases of liver damage. It also calls for stronger label warnings. ([Li et al., 2025](https://doi.org/10.1002/ptr.70157)) The rat study gave aqueous root extract at 500, 1,000, or 2,000 mg per kilogram of body weight per day for four weeks. The authors set the top dose as the no-observed-adverse-effect level in adult rats, and thyroid hormone levels stayed in range even at that dose. It is a study in rats, so it cannot answer a question about people. ([Kalaiselvan et al., 2025](https://doi.org/10.3389/fphar.2025.1572025)) The two papers ask different questions. This page did not count the review's cases one by one, so its caution rests on the review's conclusion, not on a tally of incidents. ## What the sources do not settle This page does not name who first documented ashwagandha in the classical Ayurvedic texts. The Charaka and Sushruta passages were not confirmed in a primary source in this run, so they are left out. The 2011 overview confirms the tradition, not the passages. The abstracts name KSM-66 in one trial only. The 2012 stress trial and the 2015 strength trial describe their extracts without naming a brand, so this page does not attribute them to KSM-66. None of the three trial abstracts names a sponsor, and the origin of the KSM-66 extract is not confirmed here either. The safety question is still open for people. The review's caution and the rat data point in different directions, and this page could not settle which one applies to a given reader. ## Bottom line Three verified points carry the page. The human trials are short and small, and each measured a biomarker or performance outcome rather than a health outcome. The 2025 safety papers split, with a review urging caution in pregnancy and thyroid disorders and a rat study finding no reproductive toxicity at high doses. If you are pregnant, take thyroid medication, or have liver or kidney problems, ask a clinician before taking any ashwagandha product. Which classical text first names ashwagandha, and what does the passage say? The sources in this run do not say. ## Next reads - [The ashwagandha monograph](/ingredients/ashwagandha-withania-somnifera) is the ingredient reference for this root. - [The sleep and stress guide](/health/sleep-stress-complete-guide) covers the wider background that this page only touches. - [The turmeric history](/blog/history/history-of-turmeric-and-curcumin-from-ayurveda-to-isolation) follows another Ayurvedic plant from tradition to isolated compounds.