Ashwagandha Benefits

For which claims have ashwagandha benefits been measured?

The summary below shows, for each claim, the people examined and the limit together.

What does the evidence say for stress and anxiety?

Akhgarjand and colleagues pooled RCTs: from a search of PubMed, Scopus and Google Scholar up to December 2021, 12 articles (1,002 participants, age range 25–48) were found eligible. Compared with placebo, ashwagandha reduced anxiety (SMD −1.55; 95% CI −2.37 to −0.74) and stress (SMD −1.75; 95% CI −2.29 to −1.22). Heterogeneity between trials was very high (I² 93.8% and 83.1%) and the certainty of the evidence was rated low for both outcomes. ^[1]

The review’s nonlinear dose-response analysis reports a favorable effect at the 300–600 mg/day level for stress and over a range extending up to 12,000 mg/day for anxiety. This is a statistical interpretation based on the distribution of doses in the pooled trials; it is neither a personal dose recommendation nor a safety limit, and heterogeneity between trials is very high. ^[1] The same figure of 12,000 mg/day also appears in the Ministry of Agriculture and Forestry’s scientific opinion: the opinion gives the dose recommended for root powder in Ayurveda as 3.0–6.0 g/day and states that the risk of liver injury may be associated with daily doses higher than those used in traditional medicine, even use up to 12,000 mg/day. ^[8] Liver cases are covered on the ashwagandha harms page.

Does cortisol fall?

The meta-analysis by Albalawi and colleagues searched RCTs between 2012 and February 2024: seven trials for cortisol and six for the perceived stress scale (488 participants in total); trials lasting at least two weeks and using an oral dose of at least 250 mg/day were included. Cortisol fell significantly (−1.16 µg/dL; 95% CI −1.64 to −0.69; moderate heterogeneity, I² 50.9%). For perceived stress the effect was not significant (SMD −0.355; 95% CI −1.188 to 0.47). ^[2]

In the 23-RCT (1,706 patients) meta-analysis of Fornalik and colleagues, cortisol also fell (SMD −1.18). ^[4] Cortisol is a biomarker; its fall does not mean the person’s complaints decreased. This discrepancy reported by the two meta-analyses is a reason to approach the claim of stress benefit with caution.

What does the evidence say for sleep?

Cheah and colleagues searched for RCTs comparing ashwagandha extract with placebo in participants aged 18 and over (including CENTRAL, MEDLINE, SCOPUS and registry portals); five RCTs and 400 participants were analyzed. A small but significant effect was found on overall sleep (SMD −0.59; 95% CI −0.75 to −0.42; I² 62%). The effect was more pronounced in the subgroup diagnosed with insomnia, at doses of 600 mg/day and above and over 8 weeks or longer. Morning mental alertness and anxiety also improved; there was no significant effect on quality of life. The authors rated the quality of evidence for the overall sleep result as “moderate” by GRADE; all five studies were conducted in India and one was partly supported by a manufacturer. They state that data on serious adverse effects are limited and that more data are needed for long-term safety. The review was unfunded and the authors reported no competing interests. ^[3]

For other options affecting sleep: melatonin and magnesium.

Testosterone and fertility in men

In the hormone meta-analysis, ashwagandha raised testosterone in men (mean difference 57.43 ng/dL) and did not in women (5.09 ng/dL); the difference between the sexes was significant. Estradiol did not change. The authors warn of heterogeneity and limited data for some outcomes. ^[4] This is a laboratory value; that a certain testosterone rise translates into benefit for muscle, sexual function or fertility has not been shown in this meta-analysis.

For fertility, the review by Durg and colleagues included four clinical studies (five publications): because four of the five publications were observational and only one was an RCT, an RCT meta-analysis could not be done. In oligospermic men, sperm concentration, semen volume and motility increased from baseline after 90 days of treatment; testosterone and LH also rose. In the meta-analysis of the observational studies (relative to pre-treatment), semen parameters improved. The authors state that the available data are “promising” but that, because very few studies exist, they are not enough to show robustly a benefit in male infertility. ^[5]

Can it be used for the thyroid?

Sharma and colleagues randomized 50 people aged 18–50 with a TSH of 4.5–10 µIU/L (subclinical hypothyroidism) at Sudbhawana Hospital in Varanasi, India (25 to 25). The treatment group received 600 mg/day of root extract for 8 weeks and the control group starch; four people withdrew, two from each group. Ashwagandha improved TSH (p < 0.001), T3 (p = 0.0031) and T4 (p = 0.0096) levels compared with placebo. Mild and transient side effects were reported in four people (ashwagandha 1, placebo 3). ^[7]

This is a pilot, single-center, single study; the authors say it “may be useful.” In the broader hormone meta-analysis, however, no effect was found on TSH and T3, and T4 rose slightly (0.61 µg/dL). ^[4] The two results are not in the same direction. Moreover, cases of thyrotoxicosis have been reported, and people with thyroid disease are among the groups regulators recommend avoid it; details are on the harms page.

Muscle strength and recovery

In the 8-week RCT of Wankhede and colleagues, 57 men aged 18–50 with little resistance training experience took 300 mg of root extract twice a day or a starch placebo; both groups trained. In the treatment group the increase in bench press 1-RM reached 46.0 kg (placebo 26.4 kg) and the increase in leg extension 14.5 kg (placebo 9.8 kg); arm muscle area, chest circumference and body fat percentage also changed in favor of treatment; the testosterone increase was also greater in the treatment group. ^[6]

The authors state that the participants were young and untrained, that the sample was small and the study duration short, and that studies in women and older people are needed. The root extract was supplied by two companies that make products; the authors declare no conflict of interest. ^[6] The result of a single RCT therefore cannot be turned into a general conclusion that it “increases muscle strength.”

What limits do these pieces of evidence share?

• The meta-analyses themselves report high heterogeneity and low certainty of evidence. ^[1]
• Many outcomes are laboratory values (cortisol, testosterone, TSH); they are not the same as a person’s complaints or clinical outcomes. ^[2]
• Short-term studies predominate: the thyroid and muscle strength studies lasted 8 weeks. Data for long-term safety are limited. ^[3]
• In the muscle strength study the extract came from manufacturers; the thyroid study is a single-center pilot RCT. ^{[6] [7]}

This guide does not recommend a personal dose.