Ashwagandha Explained: A Beginner's Guide to What It Is, What the Research Shows, and Who Should Skip It

 

Most supplements use extracts of the root — the part used in the clinical trials.

A friend swears by it, the gummies are everywhere — but what is ashwagandha, really?

Ashwagandha has moved from Ayurvedic tradition to the front row of the supplement shelf, usually sold with two words: stress and sleep. If you have picked up a bottle, seen "KSM-66" or "Sensoril" on the label and wondered what any of it means, you are the reader this guide is for. Botanical supplements are harder to evaluate than vitamins because the plant, the extract and the dose all change the product — and ashwagandha is a perfect example.

The short version, based on the NIH Office of Dietary Supplements (ODS) fact sheet for health professionals: ashwagandha extracts have been studied in dozens of small clinical trials, mostly for perceived stress, anxiety and sleep. The results lean positive for short-term use — typically 6 to 12 weeks — at root-extract doses around 300 to 600 mg per day. But the same fact sheet flags real cautions: rare reports of liver injury, effects on thyroid hormones, and several groups who should avoid it entirely. Here is how to read the evidence like a beginner who intends to stay one step ahead of the marketing.

What is ashwagandha?

Ashwagandha is Withania somnifera, an evergreen shrub grown across Asia, Africa and parts of Europe, used for centuries in India's Ayurvedic and Unani systems as an "adaptogen" — a substance loosely defined as helping the body resist and adapt to stress. Its roots are said to smell like a wet horse ("ashwa" means horse), which is where the Sanskrit name comes from. The root's active compounds include a family of steroidal lactones called withanolides, and most commercial supplements use root extract standardised to a stated percentage of withanolides. You will also see trademarked extracts — KSM-66 (root only) and Sensoril (root and leaf) are the two most common in trials — which matters, because the studies below were done on specific extracts, not on generic powder.

What does the research show for stress and anxiety?

This is the best-studied use. A 2021 systematic review identified seven randomised trials in which 491 adults with high self-reported stress or diagnosed anxiety took ashwagandha or a placebo for 6 to 8 weeks. Compared with placebo, ashwagandha significantly reduced stress and anxiety scores on validated rating scales, reduced sleeplessness and fatigue, and lowered serum cortisol. Benefits appeared greater at doses of 500 to 600 mg per day than at lower doses (NIH ODS). Trials published since point the same way, including a 90-day study of a sustained-release root extract (300 mg daily) that found improvements in stress, sleep quality and cortisol versus placebo.

That said, context matters for a beginner. Most trials were small, short, and conducted in India, and an international task force (the World Federation of Societies of Biological Psychiatry together with the Canadian Network for Mood and Anxiety Treatments) only provisionally recommends 300 to 600 mg per day of root extract standardised to 5% withanolides for generalised anxiety disorder — explicitly noting that more data is needed for a stronger recommendation. "Promising and reasonably studied for an herb" is the fair summary; "proven treatment" is not.

What about sleep?

The species name somnifera is Latin for "sleep-inducing," and sleep is the second claim with actual trial data. A 2021 meta-analysis of five studies covering 372 adults found ashwagandha extract had a small but significant effect on improving sleep compared with placebo. The effect was more pronounced at 600 mg per day, with use lasting at least 8 weeks, and in participants who had insomnia rather than merely poor sleep. In one trial of people with insomnia, a root-and-leaf extract improved sleep quality ratings by 72% versus 29% for placebo, alongside measured improvements in sleep efficiency and time taken to fall asleep (NIH ODS). Small effect, real effect — and clearly not a sleeping pill. If poor sleep is your main issue, it is worth comparing ashwagandha with the other supplement people most often weigh for the evening wind-down in our guide to magnesium glycinate vs citrate, since the two are frequently considered for the same problem.

Key points

• Ashwagandha is a root extract (Withania somnifera); trials use standardised extracts such as KSM-66, usually 300–600 mg/day.
• Evidence is most consistent for perceived stress and anxiety over 6–8 weeks, with modest cortisol reductions (NIH ODS).
• Sleep benefits look small but real, strongest at 600 mg/day for 8+ weeks in people with insomnia.
• Safety data covers about 3 months of use; long-term safety is unknown.
• Avoid it if you are pregnant, and check first if you have thyroid or liver issues or take sedatives, thyroid or immune medication.

 

In trials, ashwagandha is a slow, weeks-long experiment — not a same-night fix.

How do people actually take it?

In the trials summarised by the NIH, the typical pattern is 300 mg of a standardised root extract once or twice daily (600 mg total in many of the positive studies), taken for at least 6 to 8 weeks before judging. Traditional root powder is also sold, but the doses used in research are much larger by weight and the taste is famously bitter, which is why capsules dominate. Practical beginner notes:

• Choose a product that names the extract and its withanolide percentage; "proprietary blend" labels hide the dose.
• Give it a defined trial — for example 8 weeks — rather than open-ended use, since safety data beyond about 3 months is lacking.
• Take it with food if it upsets your stomach; loose stools, nausea and drowsiness are the most common side effects and are usually mild.
• Treat it as an experiment with an end date, and stop if you feel worse.

Who should skip ashwagandha — or ask a doctor first?

This is the section the advertisements skip. According to the NIH ODS safety review:

• Pregnancy: Some experts advise against use because of reports suggesting a potential to cause spontaneous abortion. Several European regulators go further — Denmark banned ashwagandha in food supplements in 2023, and France's ANSES advised against it for pregnant and breastfeeding women and people with endocrine disorders in 2024.
• Thyroid conditions or thyroid medication: Ashwagandha can raise thyroid hormone levels; studies found increases in T3 and T4, and there are case reports of thyrotoxicosis that resolved after stopping. It may interact with thyroid hormone medication.
• Liver problems: There are a few reports of liver injury linked to ashwagandha products (typically 450–1,350 mg/day for 1 week to 4 months), which improved after the products were stopped. Rare, but real.
• Medication interactions: Possible interactions include sedatives, immunosuppressants, diabetes and blood-pressure medicines (NIH ODS). Men with hormone-sensitive prostate cancer are also advised by some experts to avoid it, as it may increase testosterone.

The general principle is the same one we applied in Vitamin B12 Explained: Signs You Might Be Low, Food Sources and Who Should Actually Supplement — the right question is never "is this supplement good?" but "is it appropriate for me, at this dose, alongside what I already take?"

"Natural" describes where an ingredient comes from — not whether it is risk-free for you.

One question for you

If you have tried ashwagandha, did you notice a difference in stress or sleep — and how long did you take it before deciding? If you have not tried it, what put you off?

Sources: NIH Office of Dietary Supplements, "Ashwagandha: Is It Helpful for Stress, Anxiety, or Sleep? — Health Professional Fact Sheet" (ods.od.nih.gov), including its summaries of the 2021 systematic review of stress trials, the 2021 sleep meta-analysis, and the WFSBP/CANMAT provisional recommendation; National Center for Complementary and Integrative Health (NCCIH), ashwagandha overview.

Disclaimer: This article is general information for education only and is not medical advice. Herbal supplements can interact with medicines and are not reviewed for effectiveness before sale. Talk to your doctor or pharmacist before using ashwagandha, especially if you are pregnant, have a thyroid or liver condition, or take prescription medication.

Version française : L'ashwagandha expliqué : le guide du débutant — ce que c'est, ce que montre la recherche et qui devrait l'éviter