The verdict
Our read at a glance.
Whether a herb with genuine randomized stress data also does the hormonal and strength things it is sold for, and at what hepatic cost.
- The signal
- The trial base is substantial by supplement standards. Randomized, placebo-controlled studies report reductions in perceived stress and in cortisol, and improvements in sleep quality, with continuing registered trials across stress, sleep, cognition and athletic performance. The testosterone and muscle claims rest on a much smaller and less consistent set of studies, generally small, often single-site, and with effect sizes that have not been reliably reproduced. Standardised extracts differ meaningfully from one another, so results do not transfer cleanly between products.
- The unknown
- Who is susceptible to the liver injury. Cases have occurred in people taking labelled doses of commercial products, and there is no way to predict them in advance.
- Our read
- Genuinely one of the better-evidenced supplements for stress and sleep, sold hardest for the claim it supports least. The liver signal is the part that gets omitted from the marketing entirely, and it is real enough that several regulators have already acted on it.
The mechanism
How it works.
Ashwagandha's activity is usually attributed to withanolides, a family of steroidal lactones, with the composition varying by extract and plant part - which is why root extracts and leaf-containing extracts are not interchangeable. The best-supported effect is on the hypothalamic-pituitary-adrenal axis: the herb appears to dampen the stress response and lower cortisol, which is consistent with the improvements in perceived stress and sleep seen in trials and with the adaptogen framing. The testosterone claim is generally explained as an indirect consequence, since sustained cortisol elevation suppresses the gonadal axis, so relieving that suppression could raise testosterone in a stressed person without the herb being androgenic in any direct sense. That framing also predicts what the trials show: effects that appear in stressed or subfertile populations and largely disappear in healthy, unstressed men.
Safety & regulatory boundary
The consequential part.
A supplement rather than an approved medicine. A recognised signal of herb-induced liver injury has been described in case series across multiple countries, with a characteristic cholestatic or mixed pattern, and it has prompted regulatory review and labelling requirements in several jurisdictions. It is a thyroid-active herb that can raise thyroid hormone levels, is generally advised against in pregnancy, and has immunomodulatory activity that raises questions in autoimmune disease.
What's next
What we're watching.
Regulatory decisions on mandatory liver warnings, and any adequately powered trial of the testosterone claim.
Context
Why this is discussed.
It is the default supplement recommendation for stress, sleep and testosterone, and it has more human trials behind it than almost anything else on the shelf.
The evidence base
21 cited references.
Regulatory & labels1
ProBLEN (FDA label) · 2021
Registered trials8
ClinicalTrials.gov · NA · COMPLETED · 2025-02-14
ClinicalTrials.gov · NA · COMPLETED · 2025-01-16
ClinicalTrials.gov · PHASE1/PHASE2 · RECRUITING · 2025-01-28
ClinicalTrials.gov · NA · RECRUITING · 2026-07-20
ClinicalTrials.gov · PHASE2 · RECRUITING · 2023-09-23
ClinicalTrials.gov · NA · COMPLETED · 2025-10-20
ClinicalTrials.gov · NA · NOT_YET_RECRUITING · 2026-06
ClinicalTrials.gov · NA · COMPLETED · 2023-05-24
Indexed literature (PubMed)12
Speers AB et al. · Curr Neuropharmacol · 2021
Arumugam V et al. · Explore (NY) · 2024
Paul S et al. · Biomed Pharmacother · 2021
Wiciński M et al. · Nutrients · 2025
Mandlik Ingawale DS et al. · J Diet Suppl · 2021
Smith SJ et al. · J Psychopharmacol · 2023
Wiciński M et al. · Int J Mol Sci · 2023
Dar NJ et al. · Cell Mol Life Sci · 2015
Jhooty S et al. · Amyotroph Lateral Scler Frontotemporal Degener · 2024
Choudhary D et al. · J Diet Suppl · 2017
Akhgarjand C et al. · Phytother Res · 2022
Gopal S et al. · J Obstet Gynaecol Res · 2021
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