All 16 chapters on one page, in order. Read straight through, or jump to a chapter below.
Read one chapter at a time
Ashwagandha is used as a restorative for the nervous system, and the modern evidence follows that reading. It may modestly reduce perceived stress and lower cortisol, and trial participants report sleeping better.
It has also been studied for exercise performance and recovery.
Either way the gains are measured over weeks of steady use.
Ashwagandha (Withania somnifera) is one of the most studied herbs in this group. Its name in Sanskrit means 'smell of horse' — a nod both to its earthy aroma and traditional reputation for restoring vigor. Modern trials look at stress, sleep, cortisol, and exercise recovery. Herbalists call plants like this 'adaptogens', a loose label for plants said to help the body cope with stress. The label isn't itself evidence of benefit.
Ashwagandha may modestly reduce perceived stress and lower cortisol. Better sleep quality is the other consistent finding, and for most people it's the reason they take it.
Unani temperament: Warm & Dry (slightly moistening on the tissues) (2nd degree). Ashwagandha (Withania somnifera — asgand / اشواگاندا) enters Persian herbal use through Unani medicine, where it's classed as warm and dry in the second degree with a nourishing (mughadhī) after-effect on the nervous and reproductive tissues. It warms a cold-weak constitution, quiets an over-fired mind, and restores the vital heat that classical texts describe as depleted by chronic stress, prolonged illness, and old age.
Ayurvedic tradition classifies ashwagandha as a rasayana — a rebuilding root given not for a symptom but for a state: the person who is depleted, wired at night and exhausted by day, thin after long strain or illness. Because it's read as warming, grounding, and heavy, it suits vata and cold, anxious constitutions, and is moderated for people who already run hot. The classical preparation encodes this: the powder is simmered in milk with a little honey or ghee at night, taken steadily over weeks, because the effect is understood to be cumulative rather than immediate.
There is also trial evidence for exercise performance and recovery. That fits its traditional role as a restorative rather than a stimulant.
Commonly stirred into warm milk with spices, it represents the nourishing side of herbalism rather than a quick stimulant.
Ashwagandha isn't a Persian herb. Withania somnifera grows in India, Nepal and parts of the Middle East and North Africa, and its medical home is Ayurveda, where it has been used for centuries as a rasāyana — a rebuilding tonic rather than a treatment for a symptom.
Ayurveda is and remains its primary tradition. Its only documented use outside that tradition is a later, adopted one: Unani medicine, the Greco-Arabic system that absorbed Indian materia medica and gave the root the name asgand, classing it warm and dry. That adoption is the whole of its Persian-language connection — it isn't a herb of the classical Persian pharmacopoeia.
That distinction matters on this site. Where this guide says Ayurveda it means Ayurveda. Where it says Unani it means a later borrowing. Neither is relabelled as Persian medicine.
Primary compounds
Withanolides (withanolide A, withaferin A, withanoside IV/VI) — steroidal lactones, and the compounds commercial extracts are standardised to.
Sitoindosides VII–X — glycowithanolides, a sugar-bound group of the same family.
Alkaloids (isopelletierine, anaferine, cuscohygrine) — present only in small amounts.
Root polysaccharides and starches are the bulk of what plain root powder is.
Iron and trace minerals are a small but consistent load in the root powder.
Other notable constituents
Minerals: Potassium (trace)
From laboratory work, not from people taking it
In one small randomised trial in subclinical hypothyroidism, ashwagandha root extract shifted thyroid indices (TSH, T3, T4) towards the normal range compared with placebo. This is a single small study of a laboratory measure, not evidence that the root treats thyroid disease, and it isn't a reason to use it instead of or alongside thyroid medication. The same direction of effect is the reason it's a caution for people who are euthyroid or already on thyroid replacement. Rated: early research.
In laboratory and animal work, withanolides and the glycowithanolides act on stress-hormone signalling, nerve-cell growth factors and inflammatory pathways. This is the proposed explanation for the trial findings, not a demonstrated effect in people. Rated: early research.
Moderate evidence
Ashwagandha root extract (300 mg twice daily, 60 days) significantly reduced perceived stress and morning cortisol vs placebo in chronically stressed adults.Moderate evidence
Standardised ashwagandha extract (240 mg/day, 60 days) improved sleep quality and reduced anxiety in adults with insomnia vs placebo (double-blind RCT).Moderate evidence
Ashwagandha root extract (600 mg/day, 8 weeks) increased muscle strength and size vs placebo in resistance-trained men (randomised, double-blind).Moderate evidence
Systematic review (a careful summary of all the studies on a question) and meta-analysis (a study that pools the results of many trials): ashwagandha reduces anxiety symptoms across 5 RCTs, with the strongest signal at 12-week, ≥600 mg/day dosing.Moderate evidence
Early research
Case-series report of ashwagandha-associated hepatic injury (five patients, resolved on withdrawal) — supports caution with concentrated commercial extracts.Emerging evidence
The classical Ayurvedic form is different in shape though not in spirit: about half a teaspoon of plain root powder simmered in milk with a little ghee at night, taken steadily.
Capsules and standardised extracts carry many times the amount you get from food, which is why the cautions below matter more here.
Trials used standardised root extracts at 300–600 mg a day, taken with food, or in warm milk before bed when sleep was the goal. They ran for eight to twelve weeks of continuous use, so the published results describe a habit rather than a dose.
Three quite different things are sold under one name. Whole dried root is the traditional material, ground at home into a coarse churna. Root powder in a jar is the same thing, milled finer. A standardised extract is a concentrated preparation made to hit a stated percentage of withanolides.
Almost every modern trial used a standardised root extract at 300–600 mg a day. A teaspoon of plain root powder is a much weaker, differently balanced material, and it isn't a substitute for those doses — nor are the trial results transferable to it.
Read the label for two things: whether the product is root only (leaf carries a different withanolide profile) and whether an extract ratio or withanolide percentage is stated. Products that state neither are telling you nothing.
The word adaptogen was coined in mid-twentieth-century Soviet research to describe plants said to raise non-specific resistance to stress. It is a marketing-friendly category, not a regulated claim and not a demonstrated mechanism.
Calling ashwagandha an adaptogen (a traditional term for a plant said to help the body cope with stress) therefore tells you nothing about whether it works. What tells you something is the trial record — modest, mostly small, mostly 8–12 week studies on perceived stress, sleep and strength — and that record is set out in its own chapter here.
Thyroid hormone (levothyroxine) — Ashwagandha can raise free T3 and T4 in subclinical hypothyroidism; may push euthyroid or medicated patients into iatrogenic hyperthyroidism. Concentrated extracts avoided or clinician-monitored in anyone on thyroid replacement or with Graves' disease. (high concern)
Immunosuppressants (ciclosporin, tacrolimus, biologics) — Withanolides show immunostimulant activity in preclinical work; concentrated extracts avoided in solid-organ transplant recipients and active autoimmune therapy without specialist input. (high concern)
Sedatives (medicines that make you sleepy) / GABAergics (benzodiazepines, Z-drugs, alcohol) — Additive CNS depression; morning grogginess and depth-of-sleep changes commonly reported at 600 mg/day extract layered on prescription sedation. (moderate concern)
Antihypertensives — Withania somnifera has produced mild blood-pressure lowering in small trials; the direction is additive with antihypertensives at extract doses, so discuss monitoring with the prescriber before starting. (moderate concern)
Antidiabetic medication (metformin, sulfonylureas, insulin) — Withanolides show mild fasting-glucose lowering; additive with hypoglycaemics at concentrated extract doses. (low concern)
Hepatotoxic drugs / alcohol — Rare case reports of ashwagandha-associated liver injury, usually with concentrated commercial extracts; concentrated extracts are avoided alongside hepatotoxic therapy, and any jaundice, dark urine or unexplained fatigue is a reason to stop and see a clinician. (moderate concern)
Pregnancy and breastfeeding
Ashwagandha should be avoided in pregnancy. Classical Ayurvedic sources describe it as capable of provoking miscarriage, and preclinical work reports uterine-stimulant and antifertility signals; no trial has established a safe dose in any trimester. That applies to root powder, standardised extract and tincture (a liquid extract made with alcohol) alike — no daily amount has been shown to be safe.
Children
Ashwagandha is a nervine-tonic root traditionally used in Ayurveda for older children and adolescents recovering from illness (small root-powder doses in warm milk with ghee and jaggery). It isn't appropriate for infants or unmonitored paediatric use in Western supplement form; concentrated extracts, in particular, should only be given under paediatric or Ayurvedic-physician supervision.
Older adults
What has been studied: small randomised trials of standardised root extract at 300–600 mg/day, mostly over 8–12 weeks, reporting improvements in perceived stress and sleep, and — in trials combining the extract with resistance training — in muscle strength and grip. Most participants were healthy adults, and few trials were designed around people over 65, so this is a description of the evidence rather than a recommendation for routine use after 60. Older adults are also the group most likely to be on thyroid replacement, sedatives, blood-pressure or glucose-lowering medicines, all of which appear in the interaction list; anyone considering it should review those first with a clinician, and the trials give no information about use beyond about three months.
Avoid in pregnancy.
Auto-immune conditions: speak with a clinician first.
End of the Ashwagandha guide