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Ashwagandha

Adaptogen · Withania somnifera / KSM-66

13 min read 13 sources, checked November 14, 2026

In the BK-Score: Thin human evidence – human evidence 5 out of 10, safety data 6 out of 10. There are first, mostly small studies in humans.

Ashwagandha is the best-known adaptogen; meta-analyses show lower stress and cortisol scores over eight weeks. Quality of life did not improve in the same data, and the German Federal Institute for Risk Assessment warns of liver damage.

What ashwagandha is

Ashwagandha (Withania somnifera) comes from Ayurveda and is marketed as an adaptogen, that is, as an agent meant to improve adaptation to stress. Studies use standardized extracts such as KSM-66 or Sensoril.

The extracts are heterogeneous: different manufacturing processes yield different mixtures of compounds, which is why results cannot simply be transferred to another product. The efficacy studies usually run four to eight weeks. Since 2026 there have been first safety data on longer intake: a randomized trial over 24 weeks and an observational study over twelve months.

What was measured – and what was not

The studies record scores on anxiety and stress scales as well as cortisol levels. Cortisol is a surrogate marker, that is, a lab value that is only meant to reflect a process. Quality of life, by contrast, is the outcome that directly matters to the people affected.

This very separation is revealing: scale scores and the lab value move, quality of life does not – both in the same analysis.

What is well supported

  • The largest study reached its primary endpoint. Pakhale 2026 randomized 1002 people (498 versus 504), multicenter and double-blind, to 600 mg per day or placebo for eight weeks. The primary endpoint was safety, and it was reached: 5.6 percent adverse events under the active product versus 9.2 percent under placebo, 74 events in total, none serious. So fewer events occurred under ashwagandha than under placebo.
  • Anxiety and stress: significant effects in the meta-analysis. The systematic review by Bachour 2025 analyzed 15 randomized studies with 873 adults. After eight weeks, the mean difference on the Hamilton Anxiety Rating Scale was −3.52 (95% CI −6.00 to −1.04; p=0.0053) and on the Perceived Stress Scale −4.88 (−7.84 to −1.91; p=0.0013). Both confidence intervals lie entirely below zero.
  • The cortisol finding is the clearest single value. In the same analysis, cortisol fell by −2.36 (95% CI −3.26 to −1.46) at p less than 0.0001. The narrow interval points to a result that is consistent across studies and provides the biochemical anchor for the scale scores.
  • Common side effects have been recorded in a large cohort. Liver, kidney and blood values remained unchanged in the 1002 participants over eight weeks. For common events this is a solid basis; rare individual reactions fundamentally cannot be captured by a cohort of this size.
  • Tolerability over 24 weeks in a large randomized trial. Chopra 2026 assigned 1,200 healthy adults in India, double-blind, to ashwagandha root extract or placebo and followed them for 24 weeks. Tolerability and safety were at placebo level; adverse events were mostly mild gastrointestinal complaints, and none led to withdrawal. Blood count, liver and kidney values stayed within the reference range on average.

What the studies show

Meta-analysis: stress and cortisol better, quality of life not

A systematic review with meta-analysis of 15 randomized studies in 873 adults with stress or anxiety (Bachour 2025) found after eight weeks a mean difference of −3.52 on the Hamilton Anxiety Rating Scale (95 percent confidence interval −6.00 to −1.04; p=0.0053), −4.88 on the Perceived Stress Scale (−7.84 to −1.91; p=0.0013) and −2.36 for cortisol (−3.26 to −1.46; p less than 0.0001). For quality of life, the same analysis found no effect: −1.76 (−5.61 to 2.09; p=0.3698). The paper explicitly does not show that a benefit exists beyond eight weeks or that it occurs in a clinically diagnosed anxiety disorder.

Largest safety study: unremarkable over eight weeks

In a multicenter, double-blind study (Pakhale 2026), 1002 people (498 versus 504) received 600 mg per day or placebo for eight weeks. The primary endpoint was safety, and it was reached: 5.6 percent adverse events under the active product versus 9.2 percent under placebo, 74 events in total, none serious. Liver, kidney and blood values remained unchanged. The study's funding could not be verified.

Longer intake: 24 weeks randomized, twelve months observed

The longest randomized trial so far (Chopra 2026) followed 1,200 healthy adults aged 18 to 70 for 24 weeks; 1,032 completed it. Its actual question was whether ashwagandha strengthens the response to a COVID-19 vaccination – that could not be shown. On safety, ashwagandha was at placebo level, and liver and kidney values stayed within the reference range on average. Mildly raised liver values (up to 1.5 times the upper limit) occurred in 2 percent under ashwagandha and 0.7 percent under placebo. The trial was funded by India's state Ayurveda research council (CCRAS, Ministry of Ayush); several authors are affiliated with the funder.

An observational study without a control group (Salve 2026) followed 191 adults for twelve months on a standardized root extract supplied by the manufacturer. It recorded 18 mild adverse events that resolved without treatment; liver, kidney and thyroid values did not change in a clinically meaningful way. Cortisol fell, testosterone and self-reported quality of life rose. Without a comparison group, however, this cannot be separated from the placebo effect or the natural course.

Case report: jaundice after three days

A case report (Perez Perez 2026) describes a 27-year-old woman who developed jaundice after three days of intake. The liver tissue sample showed a cholestatic pattern, that is, a disturbance of bile flow. The RUCAM score, a standardized assessment scheme for the link between a drug and liver injury, was 7, which corresponds to the category probable.

Liver injury: 25 published cases

A review (McIntyre 2026) compiled the English-language, peer-reviewed case reports up to December 2025: 13 publications with 25 patients. The liver injury typically appeared after a few weeks of intake, mostly with disturbed bile flow, jaundice and itching. Most patients recovered within weeks to months after stopping; one needed a liver transplant, and three patients with pre-existing cirrhosis died. The authors describe a recognizable pattern of a rare, individually occurring liver reaction.

Hormones: thyroid and sex hormones

A review of hormonal effects (Vollmer and Brendler 2026) evaluates laboratory, animal and human data. In hypothyroidism, ashwagandha appears to raise thyroid hormones; the drop in cortisol is consistent across several studies, and there are signs of effects on testosterone in men and on estrogen and gonadotropins in women. The authors consider the data thin – high doses in animal studies, small human trials. A case report from Japan (Hayashi 2024) describes painless thyroiditis with hyperthyroidism in a previously healthy 47-year-old man after two months of intake, which resolved after stopping.

Where the data stop

  • No improvement in quality of life. In the same meta-analysis, quality of life remained unchanged; the confidence interval clearly includes zero. If you are aiming for a better everyday experience, you will find no evidence for it.
  • Efficacy beyond eight weeks not shown in controlled trials. The controlled data on stress, anxiety and cortisol end at eight weeks. The 24-week trial examined safety and vaccine response, not stress; the twelve-month study had no control group. So there are first data on safety over half a year, but not on a lasting benefit.
  • No evidence in clinically diagnosed anxiety disorder. The studies looked at adults with stress or anxiety symptoms, not at conditions requiring treatment.
  • Rare liver damage has not been ruled out. A study with 1002 participants over eight weeks cannot, mathematically, rule out events that occur less often than roughly once per 500 people. The reported cases of liver damage fall exactly within this range. The 24-week trial, with just under 600 people on ashwagandha, is too small for this as well.

Status, approval and legal

In communication 039/2024 of 2024-09-10, the German Federal Institute for Risk Assessment warns of liver damage up to acute liver failure in connection with ashwagandha products. It advises children, pregnant and breastfeeding women, and people with liver disease against taking them.

The authority's addendum is essential: no safe reference value can be derived from the data – there is no amount for which safety has been established. This text therefore contains no dosage recommendation.

As of November 2026, this communication is still the authoritative statement in Germany; there is no newer one. There is no EU-wide ban. A procedure under Article 8 of Regulation 1925/2006, through which the EU can ban or restrict a substance in foods, had not been opened as of September 2026.

Some countries go further. In 2023, Denmark became the first European country to ban ashwagandha in food supplements; the basis was a 2020 assessment by the Technical University of Denmark, which could not derive a safe amount and named possible effects on the thyroid and sex hormones. In the Netherlands, a draft (as of October 2026) would ban ashwagandha leaf and allow the root only with a warning label; objections can be filed until 7 December 2026. In Australia, the medicines regulator TGA published its second safety alert on liver injury in July 2026; it rates the risk as very rare and relies on 11 suspected cases.

Safety

The two findings only appear to contradict each other. The large study shows that among 1002 people over eight weeks, no common and no serious side effects occurred, and the 24-week trial with 1,200 people found tolerability at placebo level. The case report and the authority's warning, by contrast, concern rare but serious liver reactions. Such events systematically remain invisible in studies of this size – not because they are ruled out, but because the number of participants is not sufficient.

The case report also shows that a liver reaction can occur after only three days and is therefore not tied to long-term intake; in the review of 25 cases, it usually began after a few weeks. Jaundice, dark urine, persistent nausea or upper abdominal pain call for a medical evaluation. This text does not replace medical advice.

The second safety issue is hormones. The BfR and the Danish assessment name possible effects on thyroid and sex hormones, and the 2026 review supports this for the thyroid. With thyroid disease or thyroid medication, the question therefore belongs with a physician.

BK-Score Thin human evidence

Human evidence5
Mechanism4
Safety data6
Hype gap4
Track record of use8

There are several RCTs on stress and cortisol, mostly small, short and close to manufacturers. The mechanism remains vague. Important point for the safety data: reports of liver damage have occupied several authorities; since 2026 there is also a 24-week study with 1,200 participants and a 12-month observational study.

The score rates the state of knowledge, not the substance. A high safety-data value means well studied – not harmless. A high track-record value means used long and widely – that is not proof of efficacy.
Subjective assessment by Biohacking Kompakt based on published scoring rules – not a scientific rating and not a medical recommendation. Rules and all ratings (German)

Frequently asked questions about ashwagandha

Does ashwagandha work against stress?

On rating scales, yes; in everyday experience, not demonstrably. A meta-analysis of 15 studies with 873 adults found lower scores for anxiety, perceived stress and cortisol after eight weeks. Quality of life did not improve in the same analysis. The difference between a scale score and a noticeable benefit is the decisive point here.

Why does quality of life not improve?

That is an open question, but it is the most striking finding in the data. Anxiety and stress scales and cortisol levels capture narrowly defined measures; quality of life captures overall experience. If only the former moves, it remains unclear whether the change matters to the people affected at all. So far, only the change in measured values is established.

Is ashwagandha harmful to the liver?

The German Federal Institute for Risk Assessment warns of liver damage up to acute liver failure and does not derive a safe reference value. A case report describes a 27-year-old woman with jaundice after only three days of intake, with a cholestatic pattern in the tissue sample. A review of 25 published cases shows onset mostly after a few weeks and recovery after stopping; one patient needed a transplant, and three with pre-existing cirrhosis died. Such reactions are rare but serious and not tied to long-term intake.

But wasn't the large safety study unremarkable?

It was, and that still does not rule out rare liver damage. In the study, 1002 people received the active product or placebo for eight weeks; adverse events occurred in 5.6 versus 9.2 percent, none of them serious. Events that occur less often than roughly once per 500 people cannot, mathematically, be captured by a study of this size. The 24-week trial with 1,200 people was also unremarkable overall; mildly raised liver values, however, occurred more often under ashwagandha than under placebo, at 2 versus 0.7 percent.

Who should avoid ashwagandha?

The German Federal Institute for Risk Assessment advises children, pregnant and breastfeeding women, and people with liver disease against ashwagandha products. No safe reference value could be derived from the data. Because of possible effects on thyroid and sex hormones, medical advice is also called for with thyroid disease. This page gives no dosage or usage recommendation and does not replace medical advice; if you have existing conditions, the decision belongs with a physician.

Is ashwagandha banned in Germany?

No, neither in Germany nor EU-wide; since 2024 the BfR has warned of liver damage and advised certain groups against it. Denmark banned ashwagandha in food supplements in 2023, and in the Netherlands a draft would ban the leaf and require a warning label for the root. Australia published a second safety alert on liver injury in July 2026. As of November 2026.

How long has ashwagandha been studied?

For efficacy, up to eight weeks; for safety, now longer. The meta-analysis on stress and anxiety includes only studies of up to eight weeks and states that a benefit beyond that has not been shown. Since 2026 there has been a randomized trial with 1,200 healthy adults over 24 weeks, which found tolerability at placebo level, and an observational study with 191 people over twelve months without clinically meaningful changes in lab values. Whether the stress effect persists over months has still not been examined in controlled trials.

The podcast episode (in German)

Episode 41

Ashwagandha: the stress herb fact-checked

The podcast by Paul Höser (Episode 41) · with Paul & Paula. Three thousand years of Ayurveda meet more than sixty human studies: almost 28 % less cortisol (Chandrasekhar, Indian J Psychol Med 2012), better sleep (Langade, Cureus 2019), double the strength gain in the bench press (Wankhede, JISSN 2015), testosterone and libido data, less stress eating. Plus the honest side: the BfR liver warning, thyroid caution, sensible cycles and extract quality (KSM-66, Sensoril). Information only – not medical advice, no dosage or usage recommendation.

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Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in the hands of a physician. Last updated: 2026-11-14.