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Ashwagandha

Ashwagandha has been called the king of Ayurvedic herbs. Limited research suggests that it works well for reducing stress and anxiety. It may also modestly enhance strength performance, improve glucose metabolism, and increase testosterone levels, but more research is needed to confirm this.

Our evidence-based analysis on ashwagandha features 328 unique references to scientific papers.

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Summary of Ashwagandha

Primary information, health benefits, side effects, usage, and other important details

What is Ashwagandha?

Ashwagandha (Withania somnifera) is an herb used in Ayurveda, the traditional medicine of India. Its root has a horsey smell (in Sanskrit, ashva means “horse” and gandha means “smell”) and is said to confer the strength and virility of a horse. Various parts of the plant are used, but the most common in supplements is an extract of its roots.

What are Ashwagandha's benefits?

A number of studies suggest that it has anxiolytic (anti-anxiety) effects; studies are mostly supportive of a notable effect of ashwagandha for this purpose, and it seems to reduce cortisol levels. However, more research is needed before we can have a great deal of confidence in it or know the optimal dose. Ashwagandha may also be able to reduce insomnia, fatigue, and the symptoms of depression, but it hasn't been well-researched for these purposes.

It may increase power output in untrained subjects during resistance exercise and anaerobic running, but this observation is based on a small amount of research and more is needed. It may lead to small reductions in blood glucose, blood pressure, and LDL-cholesterol, while slightly increasing HDL-cholesterol. Additionally, it may modestly increase testosterone and sperm quality in infertile men.

What are Ashwagandha's side effects and drawbacks?

It seems to be safe, but it needs more long-term research that's specifically designed to evaluate its safety. It may cause mild drowsiness and sedation for some people.

Can I take Ashwagandha daily?

This question is difficult to answer because we currently lack a lot of long-term information from clinical trials. Because of its possible drug-like effects on neurotransmission, it's difficult to rule out unintended side-effects or a loss of potency in the long-term. However, what studies we do have generally suggest that the effects of Ashwagandha on stress/anxiety continually improve for at least for two months after the beginning of daily supplementation. Furthermore, the studies use Ashwagandha daily, and if a study finds an effect, the best way to get that same effect is to mimic the dose and dosing schedule in the study. It is unknown if taking breaks from Ashwagandha or taking it every other day will yield the same effects.

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How to Take

Medical Disclaimer

Recommended dosage, active amounts, other details

Take 300–500 mg of a root extract with meals (with breakfast, if taken all at once). More research is needed to determine if higher doses can yield greater benefits. Lower doses (50–100 mg) have been shown to help in some instances, such as reducing stress-induced immunosuppression and enhancing the effect of other anxiolytic agents.

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Human Effect Matrix

Unlocked for Examine Plus members

The Human Effect Matrix summarizes human studies to tell you what effects Ashwagandha has on your body, how much evidence there is, and how strong these effects are.

Full details are available to Examine Plus members.
Grade Level of Evidence
Robust research conducted with repeated double-blind clinical trials
Multiple studies where at least two are double-blind and placebo controlled
Single double-blind study or multiple cohort studies
Uncontrolled or observational studies only
Level of Evidence
? The amount of high quality evidence. The more evidence, the more we can trust the results.
Outcome Magnitude of effect
? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.
Consistency of research results
? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.
Notes
grade-b Notable Very High See all 9 studies
Evidence suggests potent anxiolytic effects in the context of chronic stress and anxiety disorder, with lesser potency in standard forms of anxiety not related to stress. There may be more benefit to social anxiety as well with Ashwagandha relative to other anxiolytics. More high-quality studies are needed to get an accurate assessment of how effective it is and the optimal dose.
grade-b Minor Very High See all 7 studies
Testosterone may be increased in infertile men (who have a reduction in testosterone) and men undergoing strength training, but there is currently no evidence to suggest an inherent testosterone boosting effect in otherwise normal men.
grade-c Notable Very High See all 6 studies
The decrease in cortisol noted in humans has reached 14.5-27.9% in otherwise healthy but stressed humans, which is significantly larger than many other supplements.
grade-c Notable Very High See all 4 studies
Improvements in power output have been noted in trained persons subject to a sprint test and in sedentary persons who simply took the supplement as well as untrained people who began strength training.
grade-c Notable Very High See all 5 studies
Ashwagandha appears to significantly reduce the symptoms of stress and its comorbidities (fatigue, temporary cognitive impairment, etc.) as well as biomarkers such as cortisol.
grade-c Notable High See all 4 studies
There is a decrease in total cholesterol of around 10% when ashwagandha (water extract of the roots) is ingested. It is notable, however, since this appears to occur in all persons regardless of whether they have high cholesterol or not
grade-c Minor - See study
Supplementation of 500mg of the water extract has been noted to improve intermittent sprint performance in otherwise untrained persons then subject to a training protocol.
grade-c Minor Very High See all 5 studies
A small decrease in blood glucose has been noted with ashwagandha, but evidence for people with type 2 diabetes is lacking.
grade-c Minor Very High See all 3 studies
Antidepressive effects have been found with ashwagandha, although they are less notable than the anti-anxiety effects. They may be mediated by similar mechanisms.
grade-c Minor Very High See all 4 studies
Secondary to its adaptogenic effects, ashwagandha is able to reduce the perceptions of fatigue with prolonged daily usage.
grade-c Minor Very High See 2 studies
Not overly notable, but a decrease has reached statistical significance. The studies are only on men, and it's unclear what the effect might be for women.
grade-c Minor High See all 4 studies
A slight decrease in LDL-C has been noted following ashwagandha supplementation.
grade-c Minor Very High See all 3 studies
An increase in luteinizing hormone in men has been detected with ashwagandha supplementation. It's unclear if this is the case for women.
grade-c Minor - See study
An increase in motivation has been noted to occur in a study where anxiety was reduced; it is not sure if this is a per se effect of supplementation or due to reducing anxiety.
grade-c Minor Very High See all 3 studies
Alongside improvements in all seminal parameters, ashwagandha is able to increase seminal motility as well; both are thought to underlie pro-fertility effects.
grade-c Minor Very High See 2 studies
Social dysfunction is reduced in anxious humans given ashwagandha, and animal studies suggest that this enhancement of socialization is a per se effect of supplementation.
grade-c Minor Very High See all 4 studies
Appears to enhance seminal quality (in a fairly general sense) but needs more studies against reference drugs to properly assess potency.
grade-c Minor High See all 4 studies
An improvement in well being has been noted secondary to reducing anxiety symptoms.
grade-c Minor Very High See all 5 studies
The best evidence at this point in time suggests a slight decrease in triglycerides seen with Ashwagandha supplementation, although it does not appear to extend to persons with normal triglyceride levels but occurs in those with metabolic impairments.
grade-c Minor Very High See all 3 studies
A slight increase in VO2 max has been detected in otherwise untrained persons and in elite cyclists.
grade-c Minor Very High See all 5 studies
A decrease has been noted in one study where overweight persons with anxiety were being treated, and while the 1-2kg loss over 8 weeks was significant it is not sure if this applies to otherwise normal weight non-anxious persons.
grade-c - Very High See all 4 studies
A small decrease in systolic and diastolic blood pressure has been noted in one study, but the evidence is very inconsistent and limited to people without hypertension.
grade-c - - See study
Supplementation of 2,000mg of Ashwagandha thrice daily in men with psychogenic erectile dysfunction failed to exert any benefits more than placebo.
grade-c - Very High See all 4 studies
A fairly notable increase in HDL-C has been reported with ashwagandha supplementation (17.3% over 60 days), however, the evidence is inconsistent and inadequate overall.
grade-d Notable Very High See 2 studies
Studies suggest a notable reduction that is probably dose-dependent. Note that research for this purpose currently is exclusively funded by industry.
grade-d Notable - See study
A notable reduction in anxiety-associated dry mouth has been noted in one industry-funded study, which needs to be replicated.
grade-d Notable - See study
Possible reduction in anxiety-associated palpitations in one industry-funded study. Needs to be replicated.
grade-d Notable - See study
Reduction in one industry-funded study of chronically stressed people. Needs to be replicated.
grade-d Notable - See study
There was a notable increase in people with subclinical hypothyroidism in one study that used 600 mg of a standardized extract (5% withanolides) for 8 weeks.
grade-d Notable - See study
There was a notable increase in people with subclinical hypothyroidism in one study that used 600 mg of a standardized extract (5% withanolides) for 8 weeks.
grade-d Notable - See study
In one pilot study, ashwagandha supplementation improved ratings of pain, lubrication, orgasm, satisfaction, arousal, and the total score on the Female Sexual Function Index.
grade-d Notable - See study
A reduction has been found in one study, which needs replication.
grade-d Notable - See study
In one study in people with knee joint pain, both 250 and 500 mg of a standardized extract (10% withanolide glycosides minimum) seemed to improve pain, physical function, stiffness, and swelling notably, with the 500 mg dose being more effective. Much more research is needed.
grade-d Notable - See study
There was a notable reduction in one study where patients with subclinical hypothyroidism took 600 mg of a standardized extract (5% withanolides) for 8 weeks. More research is needed.
grade-d Minor Very High See 2 studies
Appears to increase time to exhaustion on a treadmill test when given to athletes; the increase in endurance is mild but present. It has also been observed to slightly improve performance in long-distance running in untrained but athletic subjects.
grade-d Minor - See study
One small study noted a possible effect with 1,00 mg of an ashwagandha daily for 14 days.
grade-d Minor - See study
One study noted a modest increase in superoxide dismutase in healthy participants.
grade-d Minor Very High See 2 studies
Studies suggest an improvement in people cognitive impairment or bipolar disorder with the use of ashwagandha root extract.
grade-d Minor - See study
Reaction time on various cognitive tests was improved in people taking 1,000 mg of an ashwagandha extract, but accuracy wasn't.
grade-d Minor - See study
May have diuretic effects, although not to a remarkable degree.
grade-d Minor High See all 3 studies
Possible improvement in a couple of studies that administered cognitive tests, though not all studies found an effect.
grade-d
Minor
- See study
One study found an increase in the number of benchpress repetitions healthy subjects could do, but the placebo group saw a greater improvement in the number of weighted squats.
grade-d Minor Moderate See 2 studies
There was a trend to reduce fat mass over 30 days when supplemented to otherwise healthy people, but this failed to reach statistical significance. In untrained persons doing strength training, it may improve fat loss, however.
grade-d Minor Moderate See 2 studies
A slight reduction in pulse rate has been noted in otherwise healthy but anxious persons in one study, but not another.
grade-d Minor - See study
Minor T-cell activation following ingestion of Ashwagandha tinctures, needs to be replicated.
grade-d Minor Very High See all 3 studies
Self-reports of insomnia have been reduced with supplementation of ashwagandha in women undergoing chemotherapy, people with anxiety disorders, and chronically stressed people.
grade-d Minor - See study
One study noted a modest reduction in malondialdehyde levels in healthy people. More research is needed.
grade-d Minor Very High See all 3 studies
Multiple studies have noted an improvement on cognitive tests. Results are limited to people with cognitive impairment, anxiety, and bipolar disorder, and it's unclear if ashwagandha improves the memory of normal people.
grade-d Minor - See study
Improvement in one study in healthy people. Needs to be replicated.
grade-d Minor - See study
Improved exercise-induced muscle damage/recovery in untrained people as measured by plasma creatine kinase levels
grade-d Minor - See study
A slight increase in natural killer cell activity has been noted with ashwagandha supplementation.
grade-d Minor Very High See 2 studies
A decrease in pain has been noted with supplementation of ashwagandha root during chemotherapy and in osteoarthritis.
grade-d Minor Very High See 2 studies
Studies in healthy people and people with bipolar disorder have found increases, but not in accuracy.
grade-d Minor - See study
In one study in healthy, active adults, quality of life on the WHO-QOL scale was improved for physical function, psychological health, social relationships, and environmental factors.
grade-d Minor - See study
An improvement has been noted in a small study in healthy people. The results need replication.
grade-d Minor - See study
One study found a small, statistically reduction in healthy, active participants. More research is needed.
grade-d Minor - See study
A slight increase has been detected in serum DHEA sulfate (13.2%) with 60 days of ashwagandha supplementation.
grade-d Minor - See study
An improvement has been noted in one study in people with cognitive impairment.
grade-d Minor Very High See all 3 studies
There appears to be an increase in sperm count in normozoospermic men with infertility consuming 5g ashwagandha daily, with more potency seen in men who self-identify as stressed. A high potency extract has also shown increases
grade-d Minor - See study
A modest reduction compared with placebo has been noted in one study which needs to be replicated.
grade-d Minor - See study
One study found an improvement but needs to be replicated.
grade-d Minor Moderate See 2 studies
During toxicology testing in otherwise healthy persons, there was no significant alterations in white blood cell count seen with supplementation. However, another study found a statistically significant increase in healthy, active participants.
grade-d Minor - See study
A possible small effect has been noted in one study in people with cognitive impairment but needs to be replicated.
grade-d - -
grade-d - See study
In one study, body fat percentage was reduced by 0.6% after 12 weeks in a mixed-weight group. The placebo group so no notable change. Weight loss wasn't the focus of the study and more studies are needed.
grade-d - - See study
No apparent effect in one 8-week study.
grade-d - - See study
No apparent effect in one study of healthy participants.
grade-d - - See study
grade-d - - See study
No apparent effect of ashwagandha on estradiol in aging, overweight men in one study.
grade-d - - See study
Despite improvements seen in VO2 max and endurance capacities in this study, the respiratory exchange ratio (indicative of fat oxidation) was not significantly influenced.
grade-d - See study
A possible small decrease in one study in healthy, active participants. More research is needed.
grade-d Moderate See 2 studies
A slight but significant 6.3% increase in hemoglobin has been detected in otherwise healthy persons given ashwagandha daily for a period of 60 days. However, another study found a slight decrease in healthy subjects after 12 weeks.
grade-d - - See study
No apparent effect in schizophrenia patients in one study.
grade-d - Very High See 2 studies
There was a slight trend to increase lean mass in otherwise sedentary persons over 30 days, but it failed to reach statistical significance.
grade-d - Very High See 2 studies
In otherwise healthy persons, there is no significant influence on liver enzymes seen with supplementation.
grade-d - - See study
500 mg of a potent extract failed to reduce muscle soreness in healthy, recreationally active participants. These results can't be extrapolated to people with highly sore muscles or people undergoing intense physical exercise.
grade-d - Very High See 2 studies
One study in people with bipolar disorder failed to find an effect and so did one study in healthy people, despite an increase in processing speed.
grade-d - - See study
No apparent effect in people with schizophrenia.
grade-d - - See study
Despite alterations in power output seen, the rate of perceived exertion in otherwise sedentary persons is not affected.
grade-d - Moderate See 2 studies
Supplementation with the water extract of the roots for 30 days in otherwise healthy persons did not significantly influence red blood cell count. Another study found no change in the ashwagandha group but a slight increase in the placebo group when ashwagandha was given to healthy, active adults.
grade-d - - See study
There is no significant change in total platelet count seen with 30 days supplementation of the basic root extract in otherwise healthy persons
grade-d - - See study
grade-d - - See study
grade-d - - See 2 studies
grade-d - - See study
No apparent effect in one study in healthy, active participants taking 500 mg of a potent extract.
grade-d - Moderate See 2 studies
A reduction has been noted in one industry-funded study when 250 mg or 500 mg of an extract was used. Another study in healthy, active participants found no change.

Studies Excluded from Consideration

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Frequently Asked Questions and Articles on Ashwagandha

Does ashwagandha increase testosterone?
There is a bit of evidence that shows Ashwagandha increases testosterone, but it is not convincing.
Ashwagandha benefits for men
Ashwagandha does appear to have benefits for men specifically. These tend to centralize around testicular health and fertility while the antistress effects affect both sexes.

Things to Note

Primary Function:

Also Known As

Withania Somnifera, Indian Ginseng, Smell of Horse, Winter Cherry, Dunal, Solanaceae

Do Not Confuse With

Withania coagulans (Different Plant)

Goes Well With

  • Terminalia Arjuna for physical performance (additive)

  • Nrf2/ARE inducers (curcumin or silymarin from Milk thistle) for inducing HO-1 activity and antioxidant effects

  • ERK/p38 inhibitors (chemotherapeutic effects)

  • Notch2/4 inhibitors (chemotherapeutic effects)

  • SSRI drugs (for reducing obsession)

  • GABAergic anxiolytics (including alcohol)

  • While the root extract of ashwagandha appears to be virtually nontoxic at this point in time, high doses of isolated Withaferin A (the anticancer molecule) do possess a toxicity; in worst scenarios, it is about 4-fold higher than the therapeutic dose and difficult to reach via the root extract

  • There is insufficient evidence on drug-drug interactions with ashwagandha and P450 enzymes

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Click here to see all 328 references.