Ashwagandha

We evaluated 179 human studies on Ashwagandha, including 94 randomised controlled trials and 38 meta-analyses or systematic reviews; the controlled studies include 7,658 participants in total. As of 3 October 2026.

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1. What Is Ashwagandha? Occurrence, Origin and Forms

Ashwagandha (Withania somnifera), also known as winter cherry, is a plant of the nightshade family and has been part of India's Ayurvedic medicine for centuries. Its most important constituents are considered to be the withanolides.

The plant grows in dry regions of India, the Middle East and Africa and is cultivated mainly in India. Mostly the roots are used, less often the leaves and berries.

Products include dried root powder and extracts made with water or water-alcohol mixtures, usually standardised to a certain withanolide content. Many studies use named extracts from the root or from root and leaf.

Forms and Preparations Studied

• Root powder
• Standardised root extracts, such as KSM-66 or Shoden
• Root-and-leaf extracts, such as Sensoril
• Preparations applied to skin and hair
• Combination products with ashwagandha – the other ingredients are named in each case

Not covered on this page:

• Multi-herb Ayurvedic formulas in which the ashwagandha content is not stated → Adaptogens
• Isolated withanolides such as withaferin A in laboratory and animal experiments

2. What Does Ashwagandha Do? Results by Area

How to read the table: counted are human studies whose results concern the area. “High” means at least one meta-analysis and two controlled studies showing improvement, or at least three controlled studies of which three quarters show improvement, with at least 300 participants in total. “Moderate” means at least two controlled studies showing improvement, as a majority, or one meta-analysis alongside controlled studies. “Low” means one controlled study showing improvement. Where an area has no controlled study, the strength of evidence is at most “low” (result “reviews only” or “observational data only”). Everything else is “unclear”. A study counts as showing improvement when at least half of its outcomes in this area improved. Reviews of combination products do not count as meta-analyses; results that only describe side effects or shares of users do not count as an effect. The same study is counted only once.

3. What the Studies Show in Detail

Ashwagandha, Stress and Anxiety: Human Studies

Ashwagandha extracts lowered perceived stress more than placebo in several randomized controlled studies 47535678. Anxiety improved more than with placebo in several randomized controlled studies 4659757884. One meta-analysis confirmed advantages for perceived stress, anxiety and serum cortisol 10; another saw an advantage only for cortisol, not for perceived stress 11. Cortisol fell more than with placebo in several randomized controlled studies 537884, while in others there was no difference 4659129. Skin conductance and heart rate variability improved compared with placebo 59, as did the cortisol response to a stress test 74. Fatigue and recovery also improved in individual randomized controlled studies 85127, while another found no difference 129. Individual randomized controlled studies found no difference in perceived stress 94121124. Mainly standardized root extracts were studied, as well as root powder and extracts from root and leaf. The evidence is strong, but many studies are small and short, and the extract forms are inconsistent, so it remains open which preparation and dose work most reliably.

Further studies in this area: 18 20 23 25 26 31 34 38 43 44 46 47 49 50 51 52 53 54 56 59 65 67 68 71 72 74 75 76 77 78 80 82 83 84 85 87 88 94 98 101 108 109 114 117 121 122 124 127 129 130 139 140 151 152 154 156 160 161 162 165 166 171 172 174 177

Ashwagandha, Hormones and Fertility: Human Studies

In healthy men 5766 and in men with reduced sperm count 132, sperm values improved more with root extract than with placebo. Sexual function also improved more in men than with placebo in several randomized controlled studies 5766123. Testosterone rose more in men than with placebo in several randomized controlled studies 7886123129; a meta-analysis found the increase in men, not in women 4. In menopausal women, root extract alleviated complaints and lowered FSH and LH more than placebo 5876. A combination preparation of Ashwagandha with Shilajit, ginger, black pepper, Mucuna pruriens and Akarkara improved testosterone and cortisol in a controlled study 69, while a combination with Shatavari root extract showed no change in serum hormones 49. The findings apply to the form studied in each case, mostly standardized root extracts, and cannot be transferred to all preparations; long-term effects and the active ingredients responsible remain open.

Further studies in this area: 23 28 30 34 47 49 50 55 57 58 61 66 69 72 75 76 77 78 84 86 88 95 113 121 123 129 132 137 148 152 158 159 162 164 166 176

Ashwagandha and Sleep: Human Studies

In sleep problems, standardized root extracts of winter cherry showed better sleep quality, shorter sleep onset latency, longer sleep duration and higher sleep efficiency in several controlled studies 456582. The time awake after falling asleep also improved 4565. Daytime sleepiness decreased more in older people than under placebo 89; a systematic review considers ashwagandha root promising for insomnia 34. Randomized controlled trials also found better sleep quality for a sustained-release root extract 4753 and for the formulation Zenroot™ 59. For total time in bed, there was no difference 13. Some of the studies examined mixtures with melatonin 43, shatavari root extract 48 or Abelmoschus esculentus 51 or the addition to iron therapy in pregnancy 67. A controlled, non-randomized study was funded by the manufacturer 133. The strength of evidence is high, but the doses, extracts and treatment durations studied differ, and for root powder as well as preparations for application to skin and hair, reliable sleep data are lacking.

Further studies in this area: 45 47 48 50 51 53 59 65 67 68 80 81 82 83 89 104 108 109 114 116 117 124 125 128 133 147 151 153 154 160 161 162 165 166 172 174

Ashwagandha, Memory and Concentration: Human Studies

In several randomized controlled trials, ashwagandha extracts improved memory more than placebo, in healthy adults, in mild cognitive impairment and in children 538591104. Attention was also better in several controlled studies 8591105135. Working memory improved in several controlled studies 96104105135. Executive function was better than under placebo in several randomized controlled trials 91104109. Reaction time was better in several controlled studies 85104. Mental alertness was better in several controlled studies 6580128. A randomized controlled trial with a root-leaf extract with a liposomal coating found better results for word recall, image recognition and reaction time 85. A randomized controlled trial with a combination preparation of ashwagandha and piperine showed better multitasking and concentration performance 87. A randomized controlled trial with a combination preparation of ashwagandha and Andrographis paniculata found better attention and concentration performance 101. A meta-analysis found advantages for memory, attention, executive function and visuospatial abilities 5; a systematic review evaluates the studies as early indications 35. The studies examined predominantly adults, some with mild cognitive impairment, children and adolescents with ADHD as well as healthy older people. It remains open which ingredients and dosages are decisive for the effects.

Further studies in this area: 87 91 96 101 104 105 108 109 116 122 128 135 140 162 165 170

Ashwagandha, Physical Performance and Muscle Strength: Human Studies

With strength training, maximum strength increased more under ashwagandha extracts than under placebo in several randomized controlled trials 616286131. Maximum oxygen uptake as a measure of endurance increased more than under placebo in several randomized controlled trials 616292106127. Muscle circumference also increased more 6286, and creatine kinase as a marker of muscle stress decreased 86106; a randomized controlled trial with interval training found no difference in endurance 111. A meta-analysis found better muscle strength in physically active people, but no difference in untrained people 5, and a randomized controlled trial showed no difference in muscle soreness 99. A systematic review considers an additional benefit to strength training possible, but rates the certainty of evidence as low 16; many studies are small and short.

Further studies in this area: 61 62 69 86 89 92 99 106 111 116 118 127 131 142 157 160 162 166

Ashwagandha, Metabolism, Blood Sugar and Weight: Human Studies

In overweight and chronic stress, standardized root extracts improved body weight and body mass index in several randomized controlled trials 5688. Body composition also improved: a root extract lowered body fat percentage in young men with strength training 86, an aqueous extract of root and leaf (Sensoril®) improved the android/gynoid ratio in recreationally active men 131. In the lipid profile, triglycerides decreased under a standardized extract 75 and several cholesterol values under a mixture with Syzygium cumini 134; neither of the two summaries mentions a comparison with the control group. In a randomized controlled trial with interval training, lipids and body composition remained unchanged 113. A meta-analysis found no influence on body weight and body fat percentage 5, and milk enriched with tryptophan did not change body composition 117. Ashwagandha slightly lowered fasting blood glucose compared with placebo in a meta-analysis, with very low certainty of evidence 8.

Further studies in this area: 86 88 113 117 131 134 137 143 152 166 169

Ashwagandha and Thyroid: Human Studies

For the thyroid, the studies show no uniform picture: a randomized controlled trial with root extract found an improvement in thyroid hormones in adults with subclinical hypothyroidism 90, and a systematic review reports more favorable values under ashwagandha than under placebo in primary hypothyroidism 14. This is contrasted by randomized controlled trials that found no difference in the thyroid hormone profile in healthy adults under standardized root extracts 6495. The strength of evidence is moderate: the findings are based predominantly on small studies and reviews with inconsistently named extracts, while the meta-analysis with the most participants saw an advantage only for T4, not for TSH and T3 4. Mainly root powder and standardized root extracts were studied; for specifically defined extracts such as KSM-66 or Shoden and for combination preparations, reliable data on thyroid function are lacking. It remains open whether and at which baseline values an effect exists. It also remains open whether risks arise in thyroid patients 158.

Further studies in this area: 155 158 159

Ashwagandha, Skin and Hair: Human Studies

In hair loss, a randomized controlled trial with a topical ashwagandha root extract serum showed higher hair density as well as less hair loss, more hair growth and greater hair thickness 73. A randomized controlled trial on a lotion with standardized ashwagandha root extract found a better physician's global assessment of the skin, lower water loss, more skin moisture and higher skin elasticity, while the melanin index remained unchanged 120. The strength of evidence is moderate; the studies are small, and the results apply in each case to the form and preparation studied.

Ashwagandha: Further Outcomes in Studies

Mood and psychological well-being improved more under ashwagandha extracts than under placebo in several randomized controlled trials 46475359. Quality of life improved more than under placebo in several randomized controlled trials 5657618992; a meta-analysis on sleep, by contrast, found no influence on quality of life 12. In women, root extract improved sexual function more than placebo in several randomized controlled trials 637293. C-reactive protein decreased more than under placebo in frail older people 116, while two studies in schizophrenia found no difference in inflammatory markers 94130. In controlled studies, serious adverse events did not occur more frequently than under placebo 4064. However, a systematic review reports liver injuries in connection with ashwagandha-containing products, including multi-ingredient formulations 17. The findings apply to the form studied in each case, such as standardized root extracts, root powder or extracts of root and leaf; the robustness is high, while the transferability to other extracts and long-term safety remain open.

Further studies in this area: 24 25 26 27 29 30 32 33 34 36 37 39 40 41 42 44 45 46 47 48 49 50 51 53 54 55 56 57 58 59 60 61 63 64 67 68 70 72 73 74 75 76 77 79 80 87 88 89 92 93 94 95 97 100 101 102 103 105 109 110 111 112 114 115 116 117 118 119 120 121 123 124 125 126 127 128 129 130 131 133 136 137 138 139 140 141 142 144 145 146 148 149 150 151 152 154 155 158 159 160 161 162 163 165 166 167 169 172 173 174 175 176

4. How Is Ashwagandha Dosed? Preparation, Dose and Duration in Studies

The studies predominantly used standardized root extracts, some named specifically such as KSM-66, Shoden, AshwaSR, Prolanza or Witholytin. In addition, root powder and extracts from root and leaf were used, such as Sensoril. For skin and hair, a topical root extract serum and a lotion with standardized root extract were tested; some of the studies investigated combination preparations whose other ingredients are named in each case.

5. Is Ashwagandha Safe? Side Effects in Studies

Controlled studies reported no differences in liver, kidney and blood values or in serious adverse events 22534394064. Mild and temporary complaints such as gastrointestinal complaints, headache, drowsiness or soft stool were frequently mentioned 2343940. However, a systematic review reports liver injuries in connection with Ashwagandha-containing products, including multi-ingredient formulations 17.

6. What Remains Open: Limits of the Evidence

• Many studies are small and short; treatment durations differ considerably.
• The extracts studied have inconsistent compositions, so it remains open which preparation and dose work most reliably.
• For root powder and for preparations for application to skin and hair, robust data are lacking for several endpoints.
• The fertility findings come from men; corresponding studies for women are still pending.
• Long-term safety, especially for the liver, has not been clarified.

7. Bottom Line: What Is Established About Ashwagandha

Ashwagandha has been studied in numerous controlled human studies as root powder, as standardized root extract and as extract from root and leaf. Improvements in stress and anxiety, sleep quality, sperm parameters and sexual function, and physical performance and cognitive abilities are best supported. For body weight and blood sugar, the findings are mixed, and the data on the thyroid show no uniform picture.

The results apply in each case to the form and preparation studied and cannot readily be transferred to other extracts. Many studies are small and short, and some of the evidence comes from combination preparations. Tolerability was mostly unremarkable in the controlled studies, but a systematic review reports liver injuries in connection with Ashwagandha-containing products.