Ashwagandha

Ashwagandha is the root of Withania somnifera, a small evergreen shrub native to India, the Middle East and parts of Africa. It has been used in Ayurvedic practice for centuries, classified there as a rasayana or rejuvenating preparation.

The compounds of interest are withanolides, a group of steroidal lactones. Commercial extracts are standardised to withanolide content, commonly between 1.5 and 10 per cent depending on the extract. This variation matters enormously: a 600 mg serving of a 5 per cent extract delivers roughly ten times the withanolides of a 600 mg serving of a 0.5 per cent extract, yet both may appear similar on a label.

Two branded extracts dominate the research literature. One is a root-only extract standardised to around 5 per cent withanolides; the other is a root and leaf extract with a higher withanolide percentage used at a lower serving size. Because trials use these specific preparations, evidence does not transfer automatically to unstandardised root powder.

The most consistently proposed mechanism involves modulation of the hypothalamic-pituitary-adrenal axis, the system governing cortisol release. Trials measuring serum cortisol have generally reported reductions in participants with elevated baseline stress, and this is the most reproducible biochemical finding in the literature.

Withanolides also appear to interact with GABAergic signalling, which offers a plausible route for the reported effects on sleep onset and sleep quality, distinct from the cortisol pathway.

Additional investigated actions include antioxidant activity in neural tissue, effects on thyroid hormone output, and influence on testosterone in men. The hormonal findings are interesting but come from a smaller and more heterogeneous body of work than the stress data, and should not be presented as established.

Stress and anxiety measures represent the strongest area. Multiple randomised controlled trials using standardised extracts over 60 to 90 days have reported reductions in perceived stress scores alongside lowered serum cortisol, and meta-analyses of this literature have been broadly supportive. A recurring criticism is that a large share of trials originate from a small number of research groups and are frequently industry-funded.

Sleep research is a growing and reasonably consistent secondary area, with trials reporting improvements in sleep onset latency and subjective sleep quality, most notably in participants reporting existing sleep difficulty.

Exercise-related findings, covering strength, VO2 max and recovery markers, are more variable. Some trials report meaningful gains and others show little effect. Testosterone findings are similarly inconsistent, with effects generally reported in stressed or subfertile men rather than in healthy trained populations. Effect sizes across all of these are more modest than marketing typically implies.

Generally well tolerated in trials lasting up to three months, with mild digestive upset and drowsiness being the most frequently reported effects. Taking it with food reduces the digestive complaints in most cases.

Liver safety warrants specific attention. A number of reports of liver-related adverse effects associated with ashwagandha-containing products have appeared, and several regulators have reviewed the ingredient on that basis. The events are rare relative to the scale of use, but the signal is documented well enough that it should be disclosed rather than omitted. Anyone who has been told their liver is not working normally, or who takes medication that places a load on it, should avoid it.

It can also affect thyroid hormone output, so it may not be appropriate if your thyroid function is being monitored or medicated.