Ashwagandha turns up in most stress-relief conversations now, and for once there's real trial data behind it — not just centuries of Ayurvedic tradition. The question is what that data actually says, because “lowers cortisol” and “makes you feel less stressed” turn out to be two different claims. And right now, the UK's food safety regulator has ashwagandha under active review. Here's what the research actually supports, what it doesn't, and what to check before you buy anything.

What ashwagandha is actually being asked to do

Ashwagandha (Withania somnifera) is a root used in Ayurvedic medicine for centuries, generally as a tonic for resilience under strain — what modern researchers call an “adaptogen.” The narrower claim being tested in labs today is whether it lowers cortisol, the hormone your adrenal glands release when your body registers a threat, whether that threat is a work deadline or an actual emergency. Chronically elevated cortisol is linked to poor sleep and low mood, among other things, so a supplement that turns the dial down is an obvious thing to want to work.

The cortisol evidence, specifically

The most-cited single trial here is a 2012 study out of Asha Hospital in Hyderabad: 64 adults with self-reported chronic stress took either 300mg of KSM-66 ashwagandha extract twice a day, or a placebo, for 60 days.^[1] The ashwagandha group's serum cortisol dropped 27.9%, against a 7.9% drop in the placebo group — a meaningful gap for a two-month trial.

That's one trial, though, and supplement research doesn't always replicate outside the original lab. The stronger evidence is a 2025 systematic review pooling eight randomised controlled trials across 488 adults, which found a statistically significant average cortisol reduction compared with placebo.^[2] Across different doses and extract types, cortisol genuinely does come down.

Why “lower cortisol” isn't the same as “feel less stressed”

Here's the part most ashwagandha content skips. That same 2025 review found no significant improvement on the Perceived Stress Scale — the standard questionnaire researchers use to measure how stressed people say they feel.^[2] Cortisol fell. Reported stress, in the same participants, largely didn't move.

Maybe eight weeks isn't long enough for a hormonal shift to show up in how someone feels day to day. Maybe cortisol just isn't the right lever for subjective stress in the first place. Either read is honest. Neither one is the confident “ashwagandha crushes stress” framing you'll see on most supplement sites.

What UK regulators are actually looking at right now

This is the part worth knowing before you buy anything. The UK's Food Standards Agency ran a formal call for evidence on ashwagandha's safety in 2024 and is still working through what it means for future guidance, after risk assessments flagged possible effects on thyroid hormones, liver function and blood sugar at some doses.^[3] Denmark has already restricted ashwagandha in food supplements over similar concerns, and other EU food safety bodies are watching closely.

None of this means ashwagandha is dangerous for most healthy adults at typical doses — the concerns centre on specific groups, not a blanket problem.^[4] But it does mean skipping it in pregnancy or while breastfeeding, and talking to a doctor first if you have a thyroid condition, liver disease, or take thyroid, blood sugar or blood pressure medication. We've gone into the regulatory detail properly in a separate piece on where ashwagandha actually stands in UK law — worth a read if this is new information to you.

It's also worth knowing that ashwagandha has no authorised EFSA health claim, in either direction — inconsistent extracts and unclear mechanisms have kept it off the approved list for years.^[5] That's not the same as “unsafe.” It just means nobody gets to print a guaranteed-benefit claim on the box, including us.

If you're going to take it, what actually matters

Assuming none of the above rules you out, the studies that showed results used specific things: a standardised KSM-66 extract, roughly 600mg a day, taken consistently for eight weeks or longer.^[1] Loose ashwagandha powder from an unlabelled source, taken occasionally, isn't the same product the trials tested.

• The extract type — KSM-66 and Sensoril are the two most-studied standardised extracts; generic “ashwagandha root powder” with no extraction ratio listed is a different, less-tested product.
• The dose — most trial doses land around 600mg a day; considerably less than that is unlikely to match the results in the studies.
• Absorption support — black pepper extract (piperine) is commonly added because it measurably improves uptake of the active compounds.
• Third-party testing — a UK-manufactured product tested by an independent lab is a reasonable minimum bar for a herbal extract under this much regulatory scrutiny.

Oxford Origins' Ashwagandha KSM-66 uses that same standardised extract — a 12:1 full-spectrum KSM-66 formula, the same branded ingredient behind the Chandrasekhar trial — in a single 1281mg capsule, boosted with 95% piperine black pepper extract for absorption, and manufactured in the UK to BRC Grade AA standards. KSM-66 is, as the name on the label suggests, widely considered the gold standard of ashwagandha extract; it's the ingredient most of the research above is actually about, even if no single capsule can promise you the exact numbers from a 64-person trial.

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The honest summary

The evidence for ashwagandha and cortisol is genuinely better than most adaptogen claims you'll come across. It's just narrower than the marketing suggests. Cortisol comes down, trial after trial. Whether that translates into feeling calmer is still an open question, and whether it's right for you depends more on your health history than most supplements on the shelf. That's not a reason to write it off. It's a reason to check the label, check your own situation, and not expect a miracle in a capsule.

Frequently asked questions

How long does ashwagandha take to lower cortisol?

Most trials measure cortisol at eight weeks, including the most-cited KSM-66 study, so give it that long before judging results. Some people notice sleep or mood changes sooner, but the cortisol data specifically comes from eight-week-plus trials, not days. For general dosing and timing guidance, see our piece on the best time to take ashwagandha.

Can you take ashwagandha every day, long-term?

Most published trials run 8–12 weeks, so that's the timeframe with actual safety data behind it. Long-term daily use hasn't been studied as thoroughly, which is part of why UK regulators are still reviewing it. If you want to take it long-term, it's worth cycling off periodically and checking in with a GP, especially if you're on any regular medication.

Is ashwagandha safe to take in the UK right now?

It's legal and widely sold, but the Food Standards Agency has an active safety review open, and it isn't recommended in pregnancy, while breastfeeding, or for people with thyroid or liver conditions without medical advice. We've covered the full regulatory picture in this article.

What's the difference between KSM-66 and other ashwagandha extracts?

KSM-66 is a specific, patented 12:1 full-spectrum root extract, standardised to contain the full range of naturally occurring compounds rather than an isolated fraction. It's the extract used in most of the cortisol trials, including the 2012 Chandrasekhar study. Other products use different extraction methods, like Sensoril (leaf-and-root based), or unstandardised powder, which makes it harder to compare results between products.

Sources

1. Chandrasekhar K, Kapoor J, Anishetty S (2012), Indian Journal of Psychological Medicine — randomised controlled trial of KSM-66 ashwagandha root extract on serum cortisol and stress in adults. https://pubmed.ncbi.nlm.nih.gov/23439798/
2. Albalawi AA et al. (2025), systematic review and meta-analysis of 8 RCTs (488 adults) on ashwagandha, cortisol and perceived stress. https://journals.sagepub.com/doi/abs/10.1177/02601060251363647
3. UK Food Standards Agency — call for evidence and summary of responses on the safety of ashwagandha food supplements. https://www.gov.uk/government/consultations/summary-of-responses-to-call-for-evidence-on-ashwagandha/summary-of-responses-to-call-for-evidence-on-ashwagandha
4. Patient.info — ashwagandha safety, contraindications and drug interactions overview. https://patient.info/features/diet-and-nutrition/ashwagandha
5. NutraIngredients — overview of EU health claim law and the absence of an authorised EFSA claim for ashwagandha. https://www.nutraingredients.com/Article/2025/10/23/breaking-down-the-eu-law-on-mind-health-supplements/

At Oxford Origins, your wellbeing is our priority, and although we pride ourselves on our expertise in nutrition and supplementation, it's important to acknowledge the individuality of each person. Articles published by Oxford Origins are not intended to treat, diagnose, cure or prevent any disease, or replace the advice of your GP. We always recommend consulting with a healthcare provider if you encounter any health concerns, and we'll always be here to support you so you're never alone on your journey.