Ashwagandha is a shrub whose root has been used in Ayurveda for centuries. In small randomized trials, where people were assigned by chance to the herb or a dummy pill, it reduced stress scores and cortisol, the main stress hormone, and gave a small improvement in sleep, especially at 600 mg a day or more for at least eight weeks. But it has been linked to rare cases of liver injury, it can affect thyroid hormones, and Denmark moved to ban it after a national risk assessment. Avoid it if you're pregnant, have liver or thyroid disease, or an autoimmune condition, unless your doctor approves.
- SymptomFeeling stressed, wired and sleeping badly
- Before thatStress hormones stay high, especially at night
- Before thatThe body's stress-response system stays switched on
- RootChronic stress keeps cortisol elevated
What ashwagandha is
Ashwagandha (Withania somnifera) is a small shrub whose root is a cornerstone of rasayana, Ayurveda's branch of rejuvenation. It's classed as an adaptogen, a traditional term for herbs said to help the body handle stress. Today it's one of the best-selling supplements worldwide.
Following stress upstream
When you're stressed, your brain signals your adrenal glands to release cortisol, a hormone, or chemical messenger, that mobilizes energy for a fight-or-flight response. That's useful in short bursts. When stress never lets up, cortisol stays high, sleep suffers, blood sugar rises and recovery slows. That's the upstream problem ashwagandha is said to act on.
What the trials show
Stress and cortisol
A · Small trialsIn a 60-day trial of 64 adults with chronic stress, those taking 300 mg of root extract twice a day had significantly lower stress scores and lower blood cortisol than those on a placebo, a dummy pill.[1] Encouraging, but it was a single small study using one company's extract.
Sleep
A · Meta-analysis, small effectA meta-analysis, a study combining many studies, of five trials with 400 people found a small but significant improvement in overall sleep, larger in people with insomnia, at doses of 600 mg a day or more, and after eight weeks or more.[2]
Testosterone, muscle, longevity
B/C · LimitedSome small studies suggest effects on testosterone (the main male sex hormone) and strength, but evidence is thinner and often industry-funded. No human evidence shows it slows aging.
The safety side
Liver injury. In a case series from Iceland and the US national network that tracks drug-related liver injury, five people developed liver injury after taking ashwagandha products, typically with jaundice (yellowing of the skin and eyes) and severe itching, 2 to 12 weeks after starting. None developed liver failure, and liver tests returned to normal within a few months after stopping.[3] More cases have been reported since. It's rare, but real.
Regulators disagree. A 2020 risk assessment for Denmark's food authority concluded there wasn't enough evidence to set a safe intake level, and Denmark moved to ban ashwagandha products. Researchers and industry have criticized that assessment's methods, and most other countries still allow it.
Who should avoid it unless a doctor approves:
- People who are pregnant or breastfeeding.
- People with liver disease or a history of drug-related liver injury.
- People with thyroid conditions or on thyroid medication, since it can raise thyroid hormone levels.
- People with autoimmune diseases, since it may stimulate the immune system, the body's defense network.
- People taking sedatives, blood pressure, diabetes or immune-suppressing drugs.
Ashwagandha is a gentle, natural herb that's safe for everyone.
It has real evidence for stress and sleep, and real, if rare, risks for the liver and thyroid. It's a potent herb, not a vitamin.
The bottom line
Ashwagandha is one of the few Ayurvedic herbs with decent human evidence, for stress and modestly for sleep. It's not a longevity drug, and it isn't risk-free. If you try it, choose a third-party tested root extract, talk to your doctor first, stop if you notice yellowing skin or dark urine, and don't forget the bigger levers for stress and sleep: exercise, daylight and a steady sleep routine. See the bigger picture in Ayurveda and longevity.
Frequently asked questions
How long does ashwagandha take to work?
Most trials ran for 6 to 12 weeks. In a sleep meta-analysis, benefits were clearer at 8 weeks or more. Don't expect an immediate effect like a sleeping pill.
Can ashwagandha damage the liver?
Rarely, yes. Case reports from several countries describe liver injury, usually with jaundice (yellowing skin and eyes) appearing weeks to months after starting. Most recovered after stopping. Stop and see a doctor if you notice yellow skin, dark urine or severe itching.
Does ashwagandha affect the thyroid?
It can raise thyroid hormone levels in some people. That matters if you have a thyroid condition or take thyroid medication; check with your doctor.
Why did Denmark ban ashwagandha?
A 2020 Danish risk assessment concluded there wasn't enough evidence to set a safe intake level, citing concerns such as effects on hormones and pregnancy. The assessment has been disputed by researchers and industry, and other countries haven't followed with bans.
Sources
- Chandrasekhar K, Kapoor J, Anishetty S. A prospective, randomized double-blind, placebo-controlled study of safety and efficacy of a high-concentration full-spectrum extract of ashwagandha root in reducing stress and anxiety in adults. Indian Journal of Psychological Medicine, 2012.
- Cheah KL, et al. Effect of ashwagandha (Withania somnifera) extract on sleep: a systematic review and meta-analysis. PLoS ONE, 2021.
- Björnsson HK, et al. Ashwagandha-induced liver injury: a case series from Iceland and the US Drug-Induced Liver Injury Network. Liver International, 2020.