Every Ashwagandha Trial Seems to Work. That's the Problem.

LONGEVITY LATEST ISSUE 18 COMPANION · 8 JULY 2026

LONGEVITY LATEST · DEEP DIVE

Every Ashwagandha Trial Seems to Work. That's the Problem.

Dozens of clinical trials, nearly all positive — and in supplement research, a batting average that good is a symptom, not a seal of approval.

By Christian Thomsen · Companion to Issue 18 · 8 July 2026 · ~7-minute read

You've read the newsletter, so you know the verdict: ashwagandha is the rare stress supplement with real trials behind it, graded B− for stress, C+ for sleep, C for the testosterone story. All true. This is the part that complicates it — not to take the grade away, but to show you why an evidence base can look almost too clean, and why "backed by dozens of studies" is a phrase you should read with one eyebrow up.

Start with the thing that should feel reassuring and, once you understand it, doesn't.

The suspicious green wall

Line up the randomised trials on ashwagandha for stress and you get a wall of positive results. Cortisol down, stress scores down, anxiety down, study after study. To a casual reader that looks like overwhelming proof. To anyone who reads trials for a living, a near-unbroken run of positive findings is itself a warning sign — because in the real world, honest research is messier than that. Good interventions still throw off null results, failed replications, studies where the effect shrinks. When they don't, it usually means something is filtering the results before you see them.

Three filters are doing the work here. The first is publication bias: small studies that come back null tend to quietly never appear, so the published record skews sunny. The second is the small-study effect: nearly every ashwagandha trial is tiny — 50, 60, 80 people — and small trials swing wildly, over-producing big, flattering numbers that bigger trials later shave down. The third is the one nobody likes to say out loud.

A perfect track record in supplement research usually means the misses were never written up — not that there weren't any.

Who runs the trials

Follow the funding. The modern human trials cluster around two branded extracts — KSM-66 (made by Ixoreal Biomed) and Sensoril (Natreon) — and a large share are run in India by investigators affiliated with, or funded by, the companies that sell them. That doesn't make the results fraudulent, and it doesn't make the compound inert; industry funds a great deal of legitimate research. But it bends the incentives at every quiet decision point: which doses to test, which outcomes to report first, which unimpressive pilot never makes it to a journal.

It also concentrates the evidence in a way that's easy to miss. "Dozens of trials" sounds like dozens of independent teams converging on a truth. In practice, a striking amount of the stress literature traces back to a limited set of extract brands and their affiliated researchers, producing many similar studies. Volume isn't the same as independence, and it's independence that makes a result trustworthy. The honest read on the stress data isn't "proven" — it's "a believable effect, measured largely by interested parties in trials too small to trust one at a time." That is precisely why the newsletter graded it B− and not B.

The word doing the heavy lifting

Now the label itself. Ashwagandha is almost never sold as "a herb that modestly lowers cortisol in short trials." It's sold as an adaptogen — a word that carries an air of ancient wisdom and modern science at once, and means far less than it implies.

The term was coined in 1947 by a Soviet scientist, Nikolai Lazarev, for substances that raise the body's "non-specific resistance" to stress; in 1968 his colleagues Brekhman and Dardymov tightened it to three criteria — harmless, non-specific in action, and "normalising," nudging whatever's out of whack back toward baseline. It began as a Cold-War hunt for something to keep people performing under strain without the crash of amphetamines.

Here's the trouble. "Improves resistance to any stressor and normalises everything" isn't a falsifiable claim — it's a tonic that does a bit of everything and nothing you can pin down. Regulators have noticed: the European Medicines Agency has written that the adaptogen concept is hard to reconcile with normal pharmacology, where a drug is expected to have a specific, measurable action. "Adaptogen" survives not because the biology demanded it, but because it's a magnificent marketing word — scientific-sounding, ancient-feeling, and vague enough to hang any promise on.

The country that said no

Which brings us to the strangest fact in the file: in 2023, Denmark banned ashwagandha in food and supplements outright.

The basis was a 2020 assessment by the Technical University of Denmark's National Food Institute, which concluded it couldn't set any intake level it could call safe, citing possible effects on sex and thyroid hormones, on reproduction, and the reports of liver injury — the same signal the newsletter's Spotlight flagged. Sweden and Finland have looked at following. For a supplement selling by the tonne, that's a remarkable line to draw.

And — because this newsletter tries to give you the argument, not a side — the industry's rebuttal is not stupid. Manufacturers and several scientists argued the Danish assessment leaned heavily on animal studies at doses far above what humans take, and read the human safety literature selectively. They have a point: the liver cases are rare, confounded by multi-ingredient products, and self-limiting. A ban is a blunt instrument for a rare, reversible signal.

So hold both. The regulator may have over-reached, and the safety signal it responded to is real. That tension — a genuinely active compound, a genuinely thin long-term safety record, and a genuinely overheated market — is the whole story of ashwagandha in one dispute.

What not to conclude

Three fences, because the easy misreadings run in both directions.

This is not "ashwagandha is a scam." The stress effect is probably real, the mechanism is plausible, and for a healthy adult wanting a short, standardised trial of it, that's a defensible choice. Softening a grade is not the same as revoking it.

It is not a reason to megadose or to stay on it forever. The safety data cover eight-to-twelve-week courses in screened volunteers, not years of daily use — and "we haven't seen harm in short trials" is not "it's proven safe long-term." Those are different sentences, and the gap between them is where the liver reports live.

And it is not medical clearance. If you're pregnant, have thyroid, liver or autoimmune disease, or take regular medication, the active pharmacology that makes ashwagandha interesting is exactly what makes it a doctor's-conversation, not a self-prescription.

The useful version is narrower than either the hype or the backlash. Ashwagandha is a mildly active compound with a real but modest stress effect, an evidence base flattered by small trials and interested funding, a marketing word built to oversell it, and a safety signal serious enough that a European regulator blinked. Take it, if you like — for a defined stretch, at a known dose, with your eyes open. Just don't mistake a wall of green ticks for the whole truth.

One thing before you go

The newsletter poll asks what you were really after when you tried it — stress, sleep, gym, or just a feeling. Reply and tell me, and tell me the honest part too: did you ever check whether it did anything? Your answers decide whether Issue 20 puts the "natural test booster" claim under its own microscope. I read every one.

This is the Issue 18 Deep Dive. Longevity Latest runs one every week — the long version of the argument the newsletter only has room to start. Next week we leave the calm shelf for the healthspan one: taurine, the amino acid a 2023 Science paper turned into an ageing headline, and whether the humans ever caught up with the mice.

Sources and further reading

1. Chandrasekhar K, Kapoor J, Anishetty S. A prospective, randomized double-blind, placebo-controlled study of safety and efficacy of a high-concentration full-spectrum extract of ashwagandha root in reducing stress and anxiety in adults. Indian Journal of Psychological Medicine. 2012;34(3):255–262. PMID: 23439798.

2. Salve J, Pate S, Debnath K, Langade D. Adaptogenic and anxiolytic effects of ashwagandha root extract in healthy adults: a double-blind, randomized, placebo-controlled clinical study. Cureus. 2019;11(12):e6466. PMID: 32021735.

3. Cheah KL, Norhayati MN, Husniati Yaacob L, Abdul Rahman R. Effect of Ashwagandha (Withania somnifera) extract on sleep: a systematic review and meta-analysis. PLoS One. 2021;16(9):e0257843. PMID: 34559859.

4. Wankhede S, Langade D, Joshi K, Sinha SR, Bhattacharyya S. Examining the effect of Withania somnifera supplementation on muscle strength and recovery: a randomized controlled trial. Journal of the International Society of Sports Nutrition. 2015;12:43. PMID: 26609282.

5. Björnsson HK, Björnsson ES, Avula B, et al. Ashwagandha-induced liver injury: a case series from Iceland and the US Drug-Induced Liver Injury Network. Liver International. 2020;40(4):825–829. PMID: 31991029.

6. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury — Ashwagandha. National Institute of Diabetes and Digestive and Kidney Diseases; updated 2020. NBK548536.

7. Sharma AK, Basu I, Singh S. Efficacy and safety of ashwagandha root extract in subclinical hypothyroid patients: a double-blind, randomized placebo-controlled trial. Journal of Alternative and Complementary Medicine. 2018;24(3):243–248. PMID: 28829155.

8. Cadegiani FA, Kater CE. Adrenal fatigue does not exist: a systematic review. BMC Endocrine Disorders. 2016;16:48. PMID: 27557747.

9. Balban MY, Neri E, Kogon MM, et al. Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Reports Medicine. 2023;4(1):100895. PMID: 36630953.

10. National Food Institute, Technical University of Denmark. Assessment of the safety of Withania somnifera (ashwagandha) in food and food supplements. 2020 — the basis for the 2023 Danish restriction; see also the published defence and critique of the assessment, International Journal of Ayurveda Research, 2024.

© 2026 FrontWave Media Ltd · Longevity Latest

This article provides general educational information and is not medical advice. Ashwagandha is pharmacologically active and can affect thyroid and sex hormones, liver function and blood sugar; it is contraindicated in pregnancy and may interact with several classes of medication. If you have a thyroid, liver or autoimmune condition, are pregnant or breastfeeding, or take regular medication, consult your physician before use, and stop and seek medical advice if you develop jaundice, dark urine or abdominal p

© 2026 FrontWave Media Ltd · Longevity Latest 1