Ashwagandha

What an adaptogen actually claims to do

"Adaptogen" is a category term, not a regulated one: it describes plants proposed to increase resistance to physical and psychological stress by modulating the hypothalamic-pituitary-adrenal axis rather than stimulating or sedating directly. Ashwagandha, a nightshade-family shrub used in Ayurvedic medicine for millennia, is the most trial-supported member of the category.

The active class is withanolides — steroidal lactones. Extracts are standardised to withanolide content, typically 2.5% or 5%, and the two extracts used in the majority of quality trials are KSM-66 (a root-only, water-based extract) and Sensoril (root and leaf, higher withanolide percentage, more sedating in practice).

The stress and cortisol evidence

This is where the evidence is best. A frequently cited 2012 randomised, double-blind, placebo-controlled trial in the Indian Journal of Psychological Medicine gave 300 mg of KSM-66 twice daily for 60 days to chronically stressed adults and reported a roughly 28% reduction in serum cortisol alongside significant improvements in perceived stress scores. Multiple subsequent trials have found reductions in the same range, and meta-analyses of anxiety endpoints report a consistent direction of effect.

Sleep is a related and reasonably supported endpoint. Trials report improved sleep onset latency and sleep quality scores, which is consistent with the plant's species name — somnifera, sleep-bearing.

The testosterone evidence, stated carefully

Several small randomised trials report increases in serum testosterone of roughly 10–15% versus placebo, generally in stressed men, overweight men, or men with fertility concerns. A trial in resistance-training men reported greater increases in testosterone and muscle mass than placebo over 8 weeks.

Two caveats are important. First, sample sizes are small — typically 40 to 60 participants. Second, a disproportionate share of the positive trials originate from a limited number of research groups in India, several with links to extract manufacturers. That does not make the findings wrong, but it means confidence should be moderate rather than high, and independent replication in larger samples is still needed.

The plausible mechanism is indirect: cortisol and testosterone have an inverse relationship, so lowering chronic cortisol may permit testosterone to rise. That is a different claim from direct androgenic stimulation.

Safety — including the liver question

Ashwagandha is well tolerated by most people. Common side effects are drowsiness and gastrointestinal upset, both dose-related.

The safety issue that deserves stating plainly: there is a growing body of case reports of idiosyncratic drug-induced liver injury associated with ashwagandha, catalogued in the NIH LiverTox database. Denmark's food authority advised against ashwagandha-containing supplements in 2020, and several other European regulators have reviewed it. The cases are rare relative to the very large number of users, usually present as cholestatic jaundice within 2–12 weeks of starting, and typically resolve after stopping. It is not a reason for panic, but it is a reason to stop immediately and seek medical advice if jaundice, dark urine, pale stools or right-upper-quadrant pain develop.

Ashwagandha should be avoided by people with autoimmune thyroid disease (it can raise thyroid hormone levels), those on thyroid or immunosuppressant medication, those with existing liver disease, and during pregnancy — it has traditional use as an abortifacient at high doses.