Ashwagandha has become the ingredient everyone name-drops the moment stress comes up — in gym forums, in group chats, on wellness TikTok, usually paired with some version of the claim that it “lowers cortisol.” That much isn’t invented. But the story behind it is narrower than the headlines suggest, and if you like knowing what a study actually found before you start taking something daily, this is worth five minutes.
What Cortisol Does — and Why Ashwagandha Gets Linked to It
Cortisol is your main stress hormone, released by your adrenal glands whenever your brain flags something as urgent — a deadline, an argument, actual danger. In short bursts, it’s useful: it sharpens focus and mobilises energy. The problem is chronic elevation, cortisol that stays high because life stays demanding, which tracks with poor sleep, low mood, and wider strain on the body over time.
Ashwagandha (Withania somnifera) is classed as an adaptogen — a category of plants used in Ayurvedic medicine for centuries on the idea that they help the body regulate its stress response rather than sedate it outright. A 2025 systematic review and meta-analysis in BJPsych Open pooled the available randomised controlled trials and found a significant effect of ashwagandha on cortisol levels compared with placebo, alongside reductions in perceived stress and anxiety scores.[1] Significant here means the effect is real and unlikely to be down to chance. It doesn’t mean dramatic, and it doesn’t mean identical for everyone who takes it.
“The premise behind adaptogens isn’t sedation. It’s regulation — helping the body’s stress response come back down once the immediate need for it has passed.”
The Study Behind the Number You’ve Probably Seen
Most of the specific percentages floating around online trace back to one trial: a 2012 double-blind, placebo-controlled study of 64 adults with a history of chronic stress, published in the Indian Journal of Psychological Medicine. Participants took 300mg of a high-concentration, full-spectrum ashwagandha root extract twice a day for 60 days. By the end, the treatment group’s serum cortisol had dropped 27.9% relative to placebo, alongside improvements across several stress and anxiety scales.[2]
That extract is now sold under the brand name KSM-66, one of the most-studied standardised ashwagandha extracts on the market. Worth being precise about what this does and doesn’t prove: it was one trial, one dose, one specific extract, in adults who were already chronically stressed. It’s not a guarantee of what happens with a different formulation, a different dose, or someone who isn’t especially stressed to start with.
If you’re going to try it, the extract and the dose matter more than most labels let on. Our Ashwagandha KSM-66 uses that same standardised, full-spectrum 12:1 root extract at 1281mg per capsule, boosted with black pepper extract (95% piperine) for absorption — one capsule, once a day, rather than a vague scoop of powder.
The UK Safety Review Most Ashwagandha Content Skips
Here’s the part most ashwagandha content leaves out. In 2024, the UK Food Standards Agency opened a call for evidence on ashwagandha specifically, citing “potential risks to health from consuming ashwagandha in food supplements” — flagging case reports linking it to effects on thyroid hormone levels and, less commonly, liver toxicity.[3] The FSA’s own toxicology committee described the liver cases as consistent with an idiosyncratic reaction: rare, and not predictable from dose alone. Denmark restricted ashwagandha in food supplements back in 2020 on similar grounds, and the UK still hasn’t settled on formal usage limits — the review is genuinely ongoing.
It’s also worth being straight that there’s no EFSA-authorised health claim for ashwagandha to point to here. The EU’s assessment of botanical health claims has been on hold since 2010, so nothing in this space carries that particular stamp — what exists is evidence from individual clinical trials, which is real, but narrower.[4] We’ve covered the fuller regulatory picture in Is Ashwagandha Legal in the UK: Regulations and Availability, if you want the detail.
If you’re pregnant, breastfeeding, on thyroid medication, or managing a liver condition, this is a genuine talk-to-your-GP-first situation, not a personal judgement call.
Taking It Sensibly
- Give it time — most trials run 8 to 12 weeks before measuring results, so four days won’t tell you much.
- Match the studied dose range — most positive trials sit between 250mg and 600mg a day of standardised extract, not a rough guess at a powder serving.
- Take it daily, not as a rescue remedy — the effect builds through consistent use rather than showing up after one dose.
- Check with your GP first if thyroid medication, pregnancy, or liver health are part of your picture.
Ashwagandha’s popularity has outpaced the caution around it, which tends to happen with anything that goes from ancient remedy to Instagram shorthand in a few years. The cortisol research is real and worth taking seriously. It’s also tied to specific extracts, specific doses, and people who were properly stressed to begin with — not a blanket promise. Read the label, give it the weeks it needs, and don’t skip the GP conversation if your history calls for it. That’s the standard worth holding it to.
Frequently asked questions
How long does ashwagandha take to work for stress?
Most clinical trials measure change at the 8 to 12 week mark, though some people report feeling a bit calmer within 2 to 4 weeks. Give it the full 8 weeks at a consistent dose before deciding whether it’s doing anything for you.
Can you take ashwagandha every day, long-term?
Most of the published trials run for 8 to 12 weeks continuously, and that’s the window the safety data actually covers well. Longer-term daily use hasn’t been studied as thoroughly, which is part of why UK regulators are still reviewing it. If you want to use it beyond a few months, cycling off periodically and checking in with your GP is the sensible approach, especially if you’re on other medication.
What’s the best time of day to take ashwagandha?
There’s no strict rule. Some people take it in the evening, since early research points to a mild calming effect; others take it with breakfast alongside other supplements, purely for consistency. We’ve gone into more detail on timing in When Is the Best Time to Take Ashwagandha for Optimal Benefits.
Is ashwagandha the same as other adaptogens like rhodiola or ginseng?
No. They’re grouped together as adaptogens because they’re all believed to help the body manage stress, but they’re different plants with different evidence bases and different safety profiles. Ashwagandha currently has the largest body of clinical research behind it for cortisol specifically, while rhodiola’s research leans more toward fatigue and mental performance. They’re not interchangeable, and combining several without guidance isn’t something we’d recommend.
Sources
- BJPsych Open — systematic review and meta-analysis of ashwagandha supplementation on cortisol, stress and anxiety in adults, cited for the pooled effect on cortisol levels. cambridge.org
- Chandrasekhar K, Kapoor J, Anishetty S (2012), Indian Journal of Psychological Medicine — the randomised, placebo-controlled trial cited for the 27.9% serum cortisol reduction figure. journals.sagepub.com
- Nutrition Insight, reporting on the UK Food Standards Agency’s 2024 call for evidence on ashwagandha safety, cited for the FSA’s thyroid/liver toxicity concerns and the Danish restriction. nutritioninsight.com
- Nutrition Insight, on the EU’s botanical health claims assessment process, cited for the absence of an EFSA-authorised health claim for ashwagandha. nutritioninsight.com
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.
