Ashwagandha: the evidence thins exactly where you are standing

Read the meta-analyses and ashwagandha looks like the best supplement in the world. Strength up, power up, testosterone up, cortisol down, sleep better, VO2 max better. Then read who was in the studies.

The effects are most pronounced in untrained individuals. In trained athletes they get smaller, and in two trials in professional and semi-professional athletes several of the headline outcomes did not appear at all.

What the aggregate evidence says

A 2021 systematic review by Bonilla and colleagues pooled randomised placebo-controlled studies covering 615 healthy participants, focused on athletic performance. The findings read like a sales page.

• Significant increases in upper and lower body one-repetition maximum
• Significant increases in relative speed and power
• Significant increases in testosterone concentration
• Significant increases in VO2 max and haemoglobin
• Significant reductions in cortisol, and improvements in muscle fatigue and sleep recovery

Doses across those studies ranged from 120 to 1,250 mg daily, drawn from three different standardised extracts. That range is wide enough to be a problem in itself: a review that pools a tenfold difference in dose is telling you the category works, not what to take.

The caveat that decides everything

The reviewers themselves flag it. The greatest limitation concerns the study population, and a separate meta-analysis found the effects were more pronounced in untrained individuals.

That is not a small footnote. An untrained person given any structured intervention improves, and the room for improvement in a professional fighter's one-rep max, sleep and VO2 max is a fraction of the room in somebody who started training last month.

One trial in actual athletes makes the point concrete.

Read that row against the list above it. What survived in trained athletes was the subjective and recovery side: stress, sleep, how recovered somebody felt. What thinned out was the hard performance output. The testosterone figure, which is what sells the product, comes from the pooled data, and the reviewers themselves flag the population it was pooled from.

The liver

This is the section that changed my own position, and it is the reason this article exists rather than a shorter one.

Cases of ashwagandha-associated liver injury have been reported from several countries independently, including Japan, Iceland, India and the United States. The published case reports describe cholestatic damage, jaundice, and in at least one case a patient requiring plasmapheresis after a year of use.

Set against that, a 12-month prospective safety study in 191 healthy adults, using a standardised root extract at 600 mg daily, found no deleterious effects on liver, kidney or thyroid function, no serious adverse events, and mild adverse events in under 10 percent of participants, all self-resolving.

Both things are true, and holding them together is the honest position.

Practical version. Dark urine, yellowing of the eyes or skin, persistent nausea, abdominal pain or discomfort, itching without a rash, unexplained fatigue: stop taking it and see a doctor. Those are the symptoms in the case reports, and they appeared weeks to months into use rather than on day one.

Where regulators have gone further

In 2023 Denmark's food authority stopped ashwagandha being sold in food supplements, after a risk assessment by the Technical University of Denmark concluded that no safe lower limit for intake could be set. The concerns it listed were effects on sex hormones and the thyroid, liver injury, and a possible risk in pregnancy.

Others have moved since. Poland has set a maximum of 3 grams a day. The Dutch public health institute has advised consumers, pregnant women above all, not to use it, and the Dutch government has proposed a ban. France's food safety agency has told people with thyroid, liver or heart conditions, pregnant women and people on sedatives to avoid it. In 2024 the heads of Europe's food safety agencies recommended starting the procedure that could lead to a ban across the EU.

The decisions are contested. Several research groups have criticised the Danish assessment for leaning on animal data and on extracts unlike the standardised root products used in human trials, where adverse events have generally been mild. A ban does not prove harm, and it does tell you that the regulators who looked hardest could not set a safe dose, which is worth knowing before you add it to a camp that is already loading your liver.

The thyroid question, in a weight-cutting sport

Ashwagandha can raise thyroid hormone levels, and thyrotoxicosis has been raised as a safety concern alongside the liver signal.

In most contexts that is a background note. In this one it is not, because a fighter in a cut is already producing thyroid changes through energy restriction, and because anybody with a diagnosed thyroid condition or on thyroid medication is in a different conversation entirely. Note that the athlete trials specifically excluded participants with thyroid conditions, liver conditions and diabetes.

That exclusion list is information.

Extract, standardisation, and why the name on the tub matters here

More than with any other supplement in the stack, the product is the intervention.

• Root only. Root-only extraction removes leaf metabolites, and the extracts with the athlete research behind them are root-based.
• Standardised to withanolides. Extracts standardised to at least 5 percent withanolides show the most consistent results. An unstandardised powder is an unknown quantity.
• A named extract. The research uses specific standardised extracts. Generic ashwagandha powder is not the thing that was studied.

Where it belongs in a camp

My guide lists ashwagandha in the pre-camp additions at 300 to 600 mg in the evening, certified source only, and stops it before the cut.

I am keeping the dose and the timing, and I am changing how it is framed.

It is not a foundation supplement. Magnesium, vitamin D and omega-3 are things a fighter is plausibly short of, with mechanisms that do not depend on being untrained. Ashwagandha is an optional addition with a real but modest case, a shrinking effect size in trained people, and a safety tail the others do not have.

So: reasonable in pre-camp if sleep and stress are genuinely a problem. Not something to take because it is on a list. Stopped through the cut, which the guide already says, both because the final phase strips everything back and because a depleted athlete is not the moment to be asking the liver to process a botanical.

Who I would say no to

• Anyone with a liver condition, a thyroid condition or diabetes. These were exclusion criteria in the trials, which is the researchers telling you something.
• Anyone already on medication for stress, sleep, mood or thyroid, without a doctor's involvement.
• Anyone who is pregnant or trying to be, which is one of the concerns the Danish, Dutch and French assessments all raised.
• Anyone who cannot find their exact product on a certification register.
• Anyone taking it to raise testosterone. That figure comes from pooled trials in healthy adults, most of them untrained, and the reviewers name the study population as their greatest limitation.

The part that is uncomfortable

Ashwagandha is one of the most researched supplements in existence and one of the few with provisional clinical recognition for anxiety, so it has earned a serious hearing.

It is also a supplement whose best evidence comes from people unlike you, whose signature claim failed to replicate in trained athletes, and which carries a liver signal that magnesium does not.

Three separate reasons to be less certain than the marketing, none of which is a reason never to take it.

If your sleep and stress are genuinely broken in camp, it is a reasonable thing to try, from a named standardised root extract on a certification register, at 600 mg, with an exit plan if you feel unwell.

If you are taking it because a list said so, take it off the list.

The other optional item in the stack, where the question is which week you want it working, is tart cherry.