Ashwagandha has gone from niche Ayurvedic root to the ingredient everyone name-drops when stress comes up — gym bags, TikTok, the bottle on your colleague's desk. Somewhere in that journey, the actual research got a bit lost. Here's what the trials on ashwagandha and cortisol actually found, and what UK regulators are currently double-checking before you take anyone's word for it.

What cortisol is actually doing

Cortisol isn't the villain it gets painted as online. It's the hormone that gets you out of bed, sharpens focus under pressure, and helps your body respond to a genuine threat. The problem is chronic elevation — cortisol that stays high long after the stressor's gone, from a demanding job, broken sleep, or the low background hum of modern life. That's the pattern ashwagandha research has actually looked at: not stress in the abstract, but measurable circulating cortisol in people who report being chronically stressed.

What the research actually shows

The trial most often cited for this claim is a 2012 study out of India: 64 adults with a history of chronic stress took either 300mg of a standardised, high-concentration ashwagandha root extract twice a day, or a placebo, for 60 days. Serum cortisol dropped by 27.9% in the ashwagandha group, against a 7.9% drop on placebo — a difference too large to put down to chance.^[1]

That single study does a lot of heavy lifting in ashwagandha marketing, so it's worth being honest about its limits: 64 people, one extract, one lab, one dose. Not nothing — but not the final word either.

A 2025 systematic review pooling seven separate trials on cortisol found the same direction of effect: a real, statistically significant reduction across studies.^[2] What it didn't find was a matching drop in how stressed people said they felt. Cortisol went down. Perceived stress, measured on standard psychological scales, mostly didn't move. That gap suggests ashwagandha is doing something real and measurable in the body, even if it isn't a guaranteed mood lift on its own — so if you're taking it hoping to feel dramatically calmer within a fortnight, the evidence doesn't promise that.

The safety conversation worth having before you buy

Ashwagandha doesn't currently carry an authorised health claim in the UK, and its safety is under active, formal review.^[3] In 2024, the Food Standards Agency opened a call for evidence on whether its sale should be restricted here, following bans and restrictions already in place across parts of Europe — Denmark has banned it in food supplements outright, citing reports of liver toxicity.^[4] The FSA's Committee on Toxicology is still working through the evidence on liver injury, thyroid effects, and blood sugar, with a formal safety statement expected in the coming months. In the meantime, the FSA has already advised pregnant women and anyone with a pre-existing liver condition to avoid ashwagandha supplements altogether.^[4]

We've gone deeper into where UK regulation currently stands, including what a restriction could mean for future availability, in Is Ashwagandha Legal in the UK: Regulations and Availability.

• Pregnant or trying to conceive — avoid it. High doses have been linked to miscarriage risk, and there isn't enough safety data at lower doses either.
• Liver condition — avoid it. This is the specific concern currently under FSA review.
• Thyroid condition or thyroid medication — check with your GP first. Ashwagandha can raise thyroid hormone levels.
• Autoimmune condition or regular medication — check with your GP first, since it may stimulate immune activity and interact with certain drugs, including some antidepressants and blood pressure medication.^[5]

If you're going to try it

The studies behind those cortisol numbers used standardised root extract — not leaf, not a vague "whole plant" blend — at doses of 300–600mg a day, taken consistently for at least eight weeks. Format matters more than most labels let on.

KSM-66 is the extract that turns up in more of these trials than any other; it's become something close to the reference point the rest of the category gets measured against. Our capsule uses it as a 12:1 full-spectrum root extract, delivered in a single 1281mg capsule a day and boosted with black pepper extract (95% piperine) for absorption.

The Golden Pick

Ashwagandha KSM-66

1281mg capsule · KSM-66 full-spectrum root extract · black pepper boosted

£12.95● OUT OF STOCK

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It's currently out of stock — you can still view the page and use the notify option to hear the moment it's back, or read the label details in full before deciding if it's right for you.

The honest version

We're not telling you to skip ashwagandha. We're asking you to read past the headline — what was actually tested, on whom, for how long — and weigh that against your own health before you order anything. A gold standard has always meant the same thing round here: it works, it's honest about what it doesn't yet know, and it earns its place on the shelf. Ashwagandha might get there. Right now, it's still proving it, and so is the UK's regulator.

Frequently asked questions

How long does ashwagandha take to lower cortisol?

The main trials measured cortisol at 60 days of consistent daily use, not sooner. Some people report feeling calmer within a couple of weeks, but the actual cortisol changes measured in research took a full two months of daily dosing to show up — there's no evidence it works faster than that.

Is it safe to take ashwagandha every day?

In the studies showing a cortisol effect, yes — daily dosing for 8 to 12 weeks was standard. But that's also the exact group the UK's Food Standards Agency is currently reviewing for longer-term safety data, so "safe" comes with more caveats than most social posts admit. If you're pregnant, have a liver condition, or take regular medication, speak to your GP before starting.

What's the difference between ashwagandha root and leaf extracts?

Root extract is what the cortisol research is based on. Leaf extracts and blended "whole plant" products haven't been studied to anywhere near the same degree, and some of the safety concerns under current review relate specifically to how the extract is processed, not just the dose taken.

What time of day should you take ashwagandha?

There isn't one studied "best" time — trials have used both morning and evening dosing successfully. We've covered the practical trade-offs of each in more detail in When Is the Best Time to Take Ashwagandha for Optimal Benefits.

Sources

1. PubMed — Chandrasekhar et al. (2012), randomised placebo-controlled trial of high-concentration ashwagandha root extract on stress and cortisol, cited for the 27.9% cortisol reduction figure. https://pubmed.ncbi.nlm.nih.gov/23439798/
2. BJPsych Open — systematic review and meta-analysis (2025) of ashwagandha supplementation on cortisol, stress and anxiety levels in adults. cambridge.org/core/journals/bjpsych-open
3. Which? — "Ashwagandha: stress buster or health risk?", on the lack of an authorised UK health claim and the FSA/Committee on Toxicology safety review. which.co.uk/news/article/ashwagandha-stress-buster-or-health-risk
4. UK Food Standards Agency — call for evidence on ashwagandha, cited for the FSA review scope and current pregnancy/liver condition advice. food.gov.uk/news-alerts/consultations/ashwagandha
5. NHS — advice on herbal medicines and potential interactions with prescribed medication. nhs.uk/tests-and-treatments/herbal-medicines

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.