Summary of results

• Stress reduction : decrease in cortisol of –14 to –20%
• Decreased anxiety : large effect (SMD ≈ –1.5).
• Improved sleep : quality, duration and ease of falling asleep.
• Strengthening cognitive abilities : memory and concentration.
• Increased strength and endurance among athletes.
• Hormonal effects :
  - Increase in the testosterone and improvement of the sperm quality .
  - Improvement of the female sexual function .
• Immune support : increase in lymphocytes , antibody And NK cells .
• Metabolic balance : regulation of blood sugar, blood lipids and possible improvement of mild hypothyroidism .
• Anti-inflammatory and antioxidant action contributing to overall well-being.

Clinically proven benefits of Ashwagandha (Withania somnifera)

Ashwagandha is a shrub used in Ayurvedic medicine, recognized as adaptogen to help the body resist stress. Many clinical studies in humans – including randomized controlled trials, systematic reviews, and meta-analyses – have explored its potential benefits. Below, we present a structured summary of the demonstrated effects of ashwagandha, by area of action, with typical doses, study durations, and significant observed results, accompanied by scientific references.

Reduced stress, anxiety and cortisol

Several randomized clinical trials (RCTs) show that ashwagandha can significantly reduce stress and anxiety compared to placebo.
Meta-analyses confirm these effects with notable improvements on psychological scales and stress hormones:

- A meta-analysis of 12 RCTs (1002 participants, 25–48 years) reports a significant decrease in anxiety (standardized effect size SMD ≈ –1.55) and perceived stress (SMD ≈ –1.75) compared to placebo. These results indicate a clinically important improvement in anxiety and stress scores in participants taking ashwagandha.

- A systematic review of 9 RCTs (558 patients) found that ashwagandha reduced the perceived stress score (PSS) by about –4.7 points and the anxiety score (Hamilton Anxiety Scale) by about –2.2 points more than placebo. Furthermore, this analysis indicates a decreased serum cortisol under ashwagandha, with a mean difference of approximately –2.6 µg/dL compared to placebo.
In practice, this corresponds to a decrease of approximately 14–20% in basal cortisol, reflecting a real attenuation of the physiological response to stress.

- The anti-stress effects appear to be dose-dependent: according to the pooled data, the benefits on anxiety would be maximal up to ~12 g/day of powder (equivalent to ~600 mg/day of concentrated extract), and the optimal effect on stress would be around 300–600 mg per day extract. In particular, several high-quality trials using 500 to 600 mg/day showed greater reductions in stress and cortisol than at lower doses.

- The duration of treatment in these studies generally ranges from 6 to 12 weeks. Significant improvements in stress/anxiety symptoms are often observed. from 4 to 8 weeks daily use. Ashwagandha is well tolerated over these durations, with few notable adverse effects (mild fatigue, minor gastrointestinal disturbances).

In short, ashwagandha has a clinically proven efficacy against chronic stress and anxiety , accompanied by an objective reduction in cortisol ( stress hormone ). The table below summarizes the main results observed:

In practice, these data mean that people taking ashwagandha see, on average, a significant reduction in their stress and anxiety (better stress management, lower perceived anxiety) as well as an objective reduction in their cortisol, compared to those taking a placebo. These anti-stress benefits of ashwagandha also contribute to other improvements (sleep, overall well-being) described later.

Improved sleep

The etymology of the name somnifera (“which brings sleep”) suggests its properties on the sleep , and human studies are beginning to confirm a modest but real beneficial effect. The available clinical trials – although few in number – indicate that ashwagandha may improve the quality and duration of sleep , especially in people with insomnia:

A 2021 meta-analysis of 5 trials (372 adults, over 6 to 12 weeks) concluded that ashwagandha significantly improved overall sleep quality compared to placebo. The measured effect was modest on average, but more pronounced at high doses (600 mg/day) and over durations ≥ 8 weeks , as well as in subjects with insomnia at baseline.

- For example, an RCT conducted in India on 150 adults (18–65 years) suffering from poor sleep showed that after 6 weeks of treatment with a standardized extract (Shoden 120 mg/d containing 21 mg of withanolides), 72% of participants taking ashwagandha reported a significant improvement in their sleep, compared to only 29% in the placebo group.
Objective measurements (by actigraphy) confirmed under ashwagandha a reduction of time to fall asleep , a increase in total sleep time and of the duration of deep sleep , as well as a reduction in nighttime awakenings.
In addition, the treated subjects noted an improvement in their quality of life general related to regained sleep.

- Another randomized trial (80 people, 8 weeks) tested 600 mg/day of a KSM-66 root extract in adults, half with insomnia and half without major sleep disturbance.
In insomniacs , ashwagandha significantly improved sleep quality, reduced time to fall asleep, increased sleep efficiency, and even decreased anxiety upon waking compared to placebo.
Interestingly, even participants without initial insomnia reported a subjectively improved sleep on ashwagandha (although their morning anxiety or alertness did not change).

- Effective doses for sleep vary from
120 mg/day (highly concentrated extract) at 600 mg/day of standardized extract, with optimal durations of 8 weeks or more .
Benefits include the sleep quality (PSQI scores, etc.), the sleep latency (falling asleep faster) and the amount of sleep (hours of sleep).
Note that the effect is more marked in people suffering from insomnia than in those with normal sleep.

Thus, for people suffering from sleep disorders (especially mild to moderate insomnia), supplementing with ashwagandha for ~2 months can provide a more restful sleep , easier falling asleep and a better feeling of recovery upon waking .
These effects are closely linked to the reduction of stress and anxiety, as ashwagandha helps the body relax for better quality sleep.

Cognitive support, concentration and memory

Ashwagandha is traditionally used as brain tonic . Clinical research, although still limited, suggests positive effects on cognition , including memory, attention and executive functions:

- A 2020 systematic review (5 clinical trials) evaluated ashwagandha for cognitive impairment. It concluded that there are preliminary clinical evidence in favor of ashwagandha to improve cognitive performance.
In the majority of studies reviewed, extracts of W. somnifera have improved memory, attention, processing speed and executive functions compared to placebo.
These effects have been observed in various populations (elderly people with mild cognitive impairment, adults with mental disorders such as schizophrenia, etc.), suggesting a potential broad benefit.

- For example, in healthy young adults, one trial showed that taking ashwagandha 225 mg per day (high concentration extract) for 30 days improved certain tests of immediate memory and attention compared to placebo.
Supplemented participants achieved better scores in alertness, sustained attention span, and executive function, while experiencing less mental fatigue.

- In seniors with mild cognitive decline, ashwagandha (usually 600 mg/day of root extract for 8 to 12 weeks) has also shown benefits.
In one RCT, subjects taking ashwagandha improved their general and immediate memory , their information processing abilities and their executive functions compared to the placebo group. For example, significant improvements were observed in tasks of logical memory and visual recall.

- Comparable results were noted in patients with cognitive disorders associated with illnesses (e.g. bipolar disorder, schizophrenia): ashwagandha as an adjuvant accelerated reaction time and improved attention more than a placebo, according to some trials.

- Proposed mechanisms include neuronal antioxidant activity and a reduction in stress (which is known to impair cognition). It is important to note that the doses tested in these studies generally range between 500 and 600 mg of extract per day , on periods of 8 to 12 weeks , which seems sufficient to observe cognitive improvement.
Globally, almost all studies available clinics report a better cognitive under ashwagandha, without side effects.

In practice, these cognitive improvements translate into a better memory capacity (e.g., recall of word lists or stories), a more sustained concentration during prolonged activities, and greater ease in performing complex or multitasking tasks.
Although research continues, ashwagandha shows promise as a natural nootropic supplement , especially for people experiencing a decline in alertness due to stress or age.

Physical performance and muscular strength

Ashwagandha is also being studied for its effects on athletic performance , muscle strength and recovery. clinical evidence suggest a benefit in these areas, which corroborates its traditional use as a fortifying tonic:

- A 2021 meta-analysis (12 trials, –13 quantitative studies) concluded that ashwagandha supplementation is more effective than placebo in improving several physical performance variables in healthy adults.
Subgroup analyses showed positive effects on both strength and muscular power , as well as cardiorespiratory endurance (VO₂max) and reduced fatigue. In other words, across all studies, the ashwagandha groups improved their athletic performance more than the placebo groups.

- Regarding muscle strength, several RCTs in young adults exercising have shown increased gains with ashwagandha.
For example, a trial of men performing weight training reported that with 600 mg/day for 8 weeks , ashwagandha resulted in significant improvements in maximal strength – including greater increases in weight lifted on the bench press and leg press compared to placebo.
Additionally, this same trial noted a muscle hypertrophy more marked (increased arm circumference) and a decrease in muscle damage indicators (lower creatine kinase) in the ashwagandha group.

- In terms of cardio-respiratory endurance, ashwagandha has also shown positive effects. Studies in athletes and sedentary people have measured a increase in VO₂max (aerobic capacity) significantly greater with ashwagandha than with placebo. For example, in a trial of healthy adults, 12 weeks of ashwagandha significantly increased VO₂max (+ ~2 mL/kg/min more than placebo), suggesting better endurance.

- Ashwagandha may also reduce fatigue and improve recovery. One review noted that it helps reduce muscle fatigue and improves post-exercise recovery.
This is attributed to its anti-stress properties (lowering cortisol) aiding faster recovery, as well as a possible reduction in exercise-induced inflammation and oxidative stress.

- The doses used in these performance trials are most often 500 to 600 mg of root extract per day , over periods of 8 to 12 weeks . Some trials tested lower doses (250–300 mg/day) and still observed positive trends, but the best results typically come from doses around 600 mg/day combined with a training program. Safety has been good in these active populations, with no serious side effects.

In practice, an athlete or individual training who takes ashwagandha can expect slightly higher progress in muscular strength (for example, lifting a few kilograms more than he would have done without supplementation), to better endurance during prolonged efforts, and to a reduction of fatigue after the effort.
These effects, although moderate, may represent a notable advantage for performance and body composition over the long term.

Fertility and hormonal health (men and women)

Ashwagandha has interesting hormonal and reproductive effects in both men and women, particularly in situations of reduced fertility or sexual dysfunction . Here are the main findings of clinical studies:

In humans:

- Ashwagandha may increase testosterone levels and sperm quality. A landmark clinical trial in men with oligospermia (low sperm count) administered 675 mg/day of root extract for 90 days. Compared to the placebo, the ashwagandha group saw a +167% increase in sperm count and +57% of their mobility after 3 months ****.
These dramatic improvements in sperm parameters were accompanied by a significant increase in reproductive hormones: serum testosterone increased by approximately +17% and luteinizing hormone (LH) by an average of +34% compared to the start of the study.
This suggests a real spermatogenic effect of ashwagandha, potentially via the reduction of testicular oxidative stress and regulation of the hypothalamic-pituitary-gonadal axis.

- Even in men without declared fertility disorders, ashwagandha can favorably modulate sex hormones. For example, a double-blind study in overweight elderly men (40–70 years) showed that after 8 weeks of taking a standardized extract (Shoden 120 mg/d, equivalent to ~21 mg of withanolides), blood testosterone had increased by ~14–15% compared to placebo (significant difference, p = 0.01).
Likewise, the DHEA-S (hormone associated with vitality) increased by approximately 18% (p = 0.005) under ashwagandha.
Although in this study subjects did not report major subjective changes in fatigue or libido over 8 weeks, the objective hormonal improvement is promising for male vitality.

- In terms of male sexual function, trials indicate a benefit on libido and satisfaction.
A recent study (2022) in men with low libido observed that with 600 mg of ashwagandha per day (300 mg BID) for 8 weeks there was a significant increase in testosterone levels as well as an improvement in the sexual desire compared to placebo.
The treated men also reported better overall sexual satisfaction . There is also some evidence that ashwagandha may help with mild erectile dysfunction by reducing stress and improving circulation, although specific data in humans is still limited and requires confirmation.

In women:

- The hormonal effects of ashwagandha in women are less studied, but its impact on female sexual dysfunction has been explored. One notable clinical trial included 50 women suffering from disorders of sexual desire and satisfaction. After 8 weeks of treatment with 600 mg/day of root extract (300 mg BID), these women experienced significant improvements in their sexual function compared to those on placebo.
Specifically, overall Female Sexual Function Index (FSFI) scores increased significantly with ashwagandha (+~5.5 points vs. placebo), reflecting a better lubrication, arousal, orgasm and satisfaction . Similarly, the sexual distress score (FSDS) decreased (therefore less sexual frustration) and the number of successful reports during the study was higher in the ashwagandha group.
No serious adverse reactions were noted, suggesting a favorable safety profile . These positive effects are attributed to the reduction of stress and anxiety in these women, as well as a possible slight androgenic effect (elevation of free testosterone) which may increase female libido.

- Regarding female fertility or other hormonal parameters (such as ovarian function, menstrual disorders, etc.), direct clinical data are very limited.
However, indirectly, by improving the sleep and by reducing cortisol, ashwagandha could help rebalance the hormonal axis female in stressed women (high cortisol can disrupt ovulation).
Preliminary studies also suggest a balancing effect on certain thyroid and adrenal parameters in women.

In summary, for the reproductive sphere, ashwagandha significantly improves spermatogenesis and male hormonal balance , making it a promising adjuvant in cases of idiopathic male infertility.
In women, it helps reduce frigidity and sexual dysfunction through better stress management and possibly mild endocrine stimulation.
These effects all converge towards a hormonal well-being general, with no apparent hormonal toxicity from short-term studies.

Immunity and immune function

Emerging research suggests that ashwagandha has properties immunomodulatory , that is to say that it could strengthen certain immune defenses while regulating the inflammatory response.
Preliminary clinical trials in healthy volunteers show quantifiable improvements in immune parameters :

- In a randomized, double-blind trial (24 healthy adults), 60 days of ashwagandha supplementation (600 mg extract per day) resulted in a significant increase in the number of white blood cells and lymphocytes compared to placebo.
From 30 days, a marked increase in ashwagandha was observed. total T lymphocytes (CD3+) , T helper cells (CD4+) , Cytotoxic T (CD8+) , as well as B lymphocytes (CD19⁺) and Natural Killer cells (CD16⁺/56⁺) .
In contrast, the placebo group showed either stagnation or even a slight decline in these immune subpopulations at the same time. Ashwagandha therefore appears to stimulate both adaptive immunity (via T and B) and innate immunity (via NK).

- At the same time, this study measured circulating immunoglobulins. After 30 days, the ashwagandha group showed a significant increase in IgA , IgG levels (including subclasses IgG2, IgG3, IgG4) and IgM , indicating a strengthening of humoral immunity.
Again, volunteers on placebo had no notable change in their Ig over the same period.
Additionally, ashwagandha modulated certain cytokines : trends towards increasing interferon gamma (IFN-γ) and IL-4 were noted, suggesting a possible harmonization of Th1/Th2 responses.

- Proposed mechanisms include ashwagandha's anti-stress effect (reducing cortisol may lift the inhibition that chronic stress has on immunity), as well as the plant's richness in
immunomodulatory withanolides. For example, some withanolides could directly activate the production of white blood cells at the bone marrow level or promote lymphocyte proliferation.

- Beyond immune cells, ashwagandha may improve resistance to infections. Although direct clinical data are lacking, one study in which older adults reported fewer infectious episodes while taking ashwagandha (anecdotally, fewer colds), correlated with increased Ig and NK cells.
Further trials are expected to confirm such clinical effects.

In short, ashwagandha seems to be able to strengthen immunity in healthy subjects, by increasing both the soldiers of the immune system (lymphocytes, NK) and the humoral weapons (antibody).
This could result in better protection against common infectious agents, although caution is needed and clinical studies focusing on infection rates should be awaited.
Nevertheless, these results support the traditional use of ashwagandha as revitalizing “rasayana” and stimulating the body's defenses.

Metabolic health (blood sugar, lipids, thyroid, etc.)

Several studies suggest that ashwagandha may improve certain aspects of metabolic health , including influencing blood sugar, lipid profile and thyroid function.

Blood sugar and diabetes:

- Ashwagandha has traditionally been used to regulate blood sugar levels, and clinical data is beginning to support a moderate anti-diabetic effect. A systematic review and meta-analysis showed that ashwagandha supplementation significantly lowers fasting blood glucose and HbA1c levels (glycated hemoglobin) in patients with diabetes or insulin resistance. These improvements suggest better control of average blood glucose levels with ashwagandha. For example, some individual studies report a reduction in fasting blood glucose levels of –10 to –15 mg/dL compared to placebo after a few months of treatment
(although these numbers vary depending on initial blood sugar levels).

- Clinical trials in patients with type 2 diabetes have noted positive trends: 500 mg of ashwagandha twice daily for 3 months often resulted in a more pronounced decrease in blood sugar than placebo, as well as a decrease in HbA1c of ~0.5–1 percentage point more than the control group (depending on baseline values). These results remain to be confirmed by larger studies, but align ashwagandha with the list of herbs with hypoglycemic potential.

- The mechanism would be multifactorial: ashwagandha improves insulin sensitivity (reduction of insulin resistance), has withanolides which would stimulate the absorption of glucose by cells, and its anti-stress effect (reduction of cortisol) indirectly helps to balance blood sugar (chronic stress promoting hyperglycemia).

Blood lipids:

- Improvements in lipid profile have been reported with ashwagandha. In trials in overweight or stressed adults, taking ashwagandha (300–600 mg/day for 8–12 weeks) resulted in a decrease in total cholesterol and LDL cholesterol compared to placebo. One review noted in particular a significant reduction in LDL (“bad cholesterol”) and total cholesterol in several studies.
For example, one study observed a reduction of approximately –10% in total cholesterol and –15% in LDL after 60 days of ashwagandha, while the placebo group showed no change.

- Similarly, a beneficial effect on triglycerides has been mentioned: at least one clinical study reports a significant reduction in plasma triglycerides under ashwagandha versus placebo.
The magnitude of this decrease varies, but can be around –10 to –20% depending on the context (e.g. in stressed patients with moderate hyperlipidemia).

- These hypolipidemic effects could result from the antioxidant action of ashwagandha (reduction of lipid peroxidation nutritionandmetabolism.biomedcentral.com ), improved thyroid function (see below), and reduced cortisol (excess cortisol can elevate lipids). Overall, ashwagandha appears to promote a healthier cardiometabolic profile, which may ultimately reduce cardiovascular risks, although this link remains to be validated.

Thyroid function:

- One of the striking results concerns the thyroid, where ashwagandha has shown the ability to improve mild hypothyroidism . A controlled trial (50 patients with subclinical hypothyroidism, slightly elevated TSH 4.5–10 µIU/L) evaluated 600 mg of ashwagandha per day for 8 weeks .
The results showed that ashwagandha normalizes thyroid hormones significantly compared to placebo.
Indeed, TSH decreased (reflecting improvement, p < 0.001), while free T₃ and T₄ hormones have increase towards optimal values (p < 0.01). At the end of the study, most patients in the ashwagandha group returned to euthyroidism (TSH returned to normal).
This result is very promising, suggesting that ashwagandha may support underactive thyroid function.

Furthermore, even in individuals without overt hypothyroidism, no deleterious effects on the thyroid have been noted. Safety studies indicate no negative changes in TSH or thyroid hormones in euthyroid subjects taking 300–600 mg of ashwagandha for 8–12 weeks.
On the contrary, in a context of stress, a slight increase in T₄ has sometimes been observed, suggesting an adaptogenic effect which optimizes thyroid function rather than pushing it into hyperthyroidism.

- The thyroid benefit of ashwagandha may contribute indirectly to other metabolic effects (the thyroid influencing basal metabolism, weight, lipids, etc.).

In summary, ashwagandha appears as a versatile metabolic adjuvant : it helps to balance blood sugar , modestly improves the lipid profile and can support thyroid function in cases of mild hypothyroidism.
These effects contribute to better overall metabolic health and could, in the long term, contribute to the prevention of cardiometabolic disorders.
Of course, ashwagandha does not replace conventional treatment for diabetes or thyroid, but it can provide an interesting natural complement, under medical supervision.

Other effects (inflammation, antioxidants, overall well-being)

In addition to the above areas, ashwagandha exerts other general beneficial effects on health, often linked to its anti-stress, anti-inflammatory and antioxidant properties:

- Anti-inflammatory effects
Ashwagandha appears to reduce some markers of inflammation . For example, studies on chronic stress have found that supplementation decreased the level of C-reactive protein (CRP) high sensitivity, a marker of systemic inflammation. In one trial, 250 mg of ashwagandha per day resulted in an approximately 36% decrease in CRP in 60 days, compared to near stagnation in the placebo group.
Another study (preprint) also noted a significant reduction in serum CRP after 8 weeks of ashwagandha, suggesting a measurable anti-inflammatory effect.
This anti-inflammatory potential is consistent with the reduction in pro-inflammatory cytokines observed in certain animal studies and with patient feedback (less joint or muscle pain).

- Antioxidant effects
Ashwagandha is rich in antioxidant compounds that protect cells from oxidative stress. Clinical trials show that it reduces lipid peroxidation markers like the malondialdehyde (MDA) . In healthy adults, taking ashwagandha has significantly decreased MDA levels in two studies, indicating less oxidative damage to membranes.
At the same time, we measured a increase in endogenous antioxidant enzymes : for example, one study reports an increase in superoxide dismutase (SOD) and total antioxidant capacity in the blood under ashwagandha.
Thus, ashwagandha acts as a free radical scavenger , which may contribute to its anti-aging and neuroprotective effects (reduction of cognitive decline linked to cerebral oxidative stress).

- Overall psychophysical well-being
Due to its combined effects (anti-stress, better sleep, hormonal support), ashwagandha often generally improves the well-being and the quality of life users.
Participants in trials have described, compared to placebo, a greater inner calm , a increased energy during the day , a better mental clarity and one overall sense of well-being .
For example, in one study of moderate stress, those taking ashwagandha felt more able to manage their stress (it became " manageable " instead of " overwhelming ") and noted simultaneous improvements in their sleep, stamina, and concentration.
Several trials using quality of life questionnaires (e.g., WHO-QOL) find rising scores with ashwagandha compared to placebo.

- Mood and depressive symptoms
Although ashwagandha is not a formal antidepressant, its action on stress and inflammation may help mood. A few pilot studies suggest a reduction in subdepressive symptoms and an improvement in overall mood . in stressed people taking ashwagandha.
This remains an area for further investigation, but it is plausible that the reduction in cortisol and improvement in sleep induced by ashwagandha translates into a better emotional stability and less irritability or discouragement.

- Other miscellaneous benefits
Ashwagandha has also been studied (often in integrative Ayurvedic medicine) for effects such as reducing pain (moderate analgesic properties), convalescence aid (feeling of vigor), and even potentially neuroprotectors (in patients with neurodegenerative disorders, still at the preliminary stage).
Furthermore, its ability to lower cortisol may make it an ally in limiting the deleterious effects of chronic stress on various organs (e.g. prevention of stress hypertension or immune erosion due to stress ).

Ultimately, Ashwagandha is distinguished by its holistic action on well-being. By reducing stress and inflammation while supporting sleep and key functions, it creates a virtuous circle that is reflected in a general well-being individuals.
This synergy of effects (physical, mental, hormonal) explains why ashwagandha is often described as a “overall invigorating tonic” in traditional medicine.
Modern scientific findings largely confirm this view, making ashwagandha a dietary supplement that is both versatile and supported by solid clinical data.

Selected references: The data presented come from recent systematic reviews, meta-analyses and clinical trials of ashwagandha: e.g. Akhgarjand et al., 2022 on stress/anxiety, Arumugam et al., 2024 on stress/cortisol, Cheah et al., 2021 on sleep, Ng et al., 2020 on cognition, Bonilla et al., 2021 on physical performance, Sharma et al., 2018 on the thyroid, Dongre et al., 2015 on female sexual function, etc. All of these studies converge to support the traditional benefits attributed to ashwagandha, now supported by modern science .