Ashwagandha Benefits: New Review of 20 Clinical Trials Reveals What It Really Does (and Doesn't Do)
Ashwagandha has become one of the most popular supplements in the world.
Walk into almost any supplement store and you'll find it promoted for everything from reducing stress and improving sleep to increasing testosterone, building muscle, sharpening focus, and boosting athletic performance.
That's impressive—but it also raises an important question:
How much of that is actually supported by research?
A new systematic review and meta-analysis published in Frontiers in Pharmacology set out to answer exactly that.
Rather than relying on a single clinical trial, researchers combined the results of 20 randomized controlled trials involving 1,249 adults to evaluate whether ashwagandha truly improves cognitive function and physical performance.
The findings are encouraging—but they also reveal where the evidence is strongest, where it's weaker, and where many marketing claims get ahead of the science.
What Is Ashwagandha?
Ashwagandha (Withania somnifera) is a medicinal plant that has been used for centuries in traditional Ayurvedic medicine.
Its roots and leaves contain a variety of biologically active compounds known as withanolides, along with alkaloids, flavonoids, and other phytochemicals believed to contribute to its health effects.
Modern research suggests these compounds may influence several physiological systems, including:
- The stress response
- Cognitive function
- Muscle performance
- Hormone regulation
- Sleep quality
- Immune function
Because of these diverse effects, ashwagandha has become one of the most studied botanical supplements available.
Why This Study Matters
One of the biggest challenges in nutrition research is that individual studies often produce conflicting results.
One trial may report dramatic benefits.
Another may find little or no effect.
That's why systematic reviews and meta-analyses are considered among the strongest forms of scientific evidence.
Instead of relying on one study, researchers combine data from multiple high-quality clinical trials to determine what the overall body of evidence shows.
In this review, investigators searched four major scientific databases and identified 20 randomized controlled trials that met strict inclusion criteria.
Together, these studies included 1,249 adult participants ranging in age from 18 to 75 years.
Researchers evaluated whether ashwagandha supplementation affected:
- Memory
- Attention and processing speed
- Executive function
- Visuospatial ability
- Global cognition
- Muscle strength
- Testosterone
- Body weight
- Body fat percentage
That makes this one of the most comprehensive evaluations of ashwagandha currently available.
Not All Ashwagandha Supplements Are Created Equal
One of the most valuable—and often overlooked—findings from this review is that the supplements used across the studies were not identical.
Researchers found considerable variation in:
- Daily dosage (225–675 mg)
- Length of supplementation (7 days to 16 weeks)
- Plant parts used (root only vs. root and leaf)
- Standardized withanolide content
- Extraction methods
Most studies used 600 mg per day, typically divided into two 300 mg doses, and many standardized their extracts to approximately 5% withanolides.
This matters because different extraction methods and withanolide concentrations may produce different physiological effects. Choosing a standardized extract from a reputable manufacturer is one of the best ways to select a product similar to those evaluated in clinical research.
Ashwagandha Improved Several Areas of Cognitive Function
One of the strongest findings from the review involved brain health.
After combining data from multiple randomized controlled trials, researchers found statistically significant improvements in:
- Memory
- Attention and processing speed
- Executive function
The analysis also suggested potential improvements in visuospatial ability after accounting for variability between studies. One individual study also reported improvements in global cognitive function, although there were not enough studies evaluating this outcome to perform a formal meta-analysis.
These findings suggest that ashwagandha doesn't simply make people "feel sharper." It may improve specific cognitive processes involved in learning, concentration, and problem-solving.
Memory
Across six clinical trials, participants taking ashwagandha demonstrated moderate improvements in memory-related tasks compared with placebo.
Attention and Processing Speed
Researchers also found improvements in attention and processing speed, suggesting participants were better able to maintain focus and respond efficiently during cognitive testing.
Executive Function
Executive function includes higher-level mental skills such as planning, decision-making, self-control, and mental flexibility.
Ashwagandha supplementation significantly improved executive function, although researchers rated the certainty of this evidence lower than the findings for memory and attention.
Ashwagandha May Help Build Strength, Especially If You Train
While many people associate ashwagandha with stress relief, this review found some of the strongest evidence for its effects on muscle strength.
After pooling results from four randomized controlled trials involving 223 participants, researchers found significant improvements in muscle strength compared with placebo.
Interestingly, the greatest benefits occurred in physically active individuals.
When researchers separated participants based on training status, those who regularly exercised experienced much larger improvements than untrained or special populations.
This suggests that ashwagandha may work best when combined with resistance training rather than acting as a substitute for exercise.
Why Might Ashwagandha Improve Strength?
Researchers believe several mechanisms may contribute.
Ashwagandha appears to influence the hypothalamic-pituitary-adrenal (HPA) axis, helping regulate the body's stress response and potentially lowering cortisol levels.
Lower cortisol may support better recovery and create a more favorable environment for muscle adaptation following training. Previous research has also linked ashwagandha with improvements in muscle recovery, hypertrophy, and exercise performance.
Although more research is needed to fully understand these mechanisms, the evidence suggests ashwagandha may help athletes get more from their training over time.
Ashwagandha Increased Testosterone
One of the most heavily advertised claims surrounding ashwagandha is that it boosts testosterone.
This review found evidence supporting a modest but statistically significant increase in testosterone levels.
Across seven randomized controlled trials involving 488 participants, ashwagandha supplementation increased serum testosterone compared with placebo.
However, it's important not to overstate this finding.
The increase was relatively modest and should not be compared to the effects of anabolic steroids or hormone replacement therapy.
Instead, the evidence suggests ashwagandha may help support healthy testosterone levels, particularly when combined with resistance training.
Ashwagandha Is Not a Weight-Loss Supplement
One of the biggest myths surrounding ashwagandha is that it helps people lose weight.
This review found little evidence to support that claim.
Researchers analyzed studies measuring changes in both body weight and body fat percentage and found no statistically significant improvements compared with placebo.
While improved recovery and training quality could indirectly influence body composition over time, current evidence does not support using ashwagandha specifically for fat loss.
Is Ashwagandha Safe?
Across all 20 clinical trials, ashwagandha was generally well tolerated.
Most participants experienced no side effects.
When adverse events occurred, they were usually mild and temporary, including:
- Mild digestive discomfort
- Nausea
- Headache
- Drowsiness
- Bloating
- Dizziness
Importantly, no serious adverse events were reported in the included studies.
Nevertheless, people who are pregnant, breastfeeding, taking prescription medications, or managing chronic health conditions should consult a healthcare professional before using ashwagandha.
What Dose Worked Best?
Although the included studies used doses ranging from 225 mg to 675 mg per day, the most common protocol was:
- 600 mg daily
- Divided into 300 mg twice per day
- Continued for approximately eight weeks
This regimen was used in many of the studies demonstrating improvements in cognition, muscle strength, and testosterone.
Because not all supplements contain the same amount of active withanolides, selecting a standardized extract from a reputable manufacturer is just as important as choosing the correct dosage.
Important Limitations
Like all scientific research, this review has limitations.
The studies used different extract formulations, dosages, treatment durations, and participant populations.
Some outcomes—such as muscle strength and body composition—were evaluated in relatively few studies.
Researchers also concluded that additional high-quality trials are needed to better understand which populations benefit most and whether different standardized extracts produce different effects.
These limitations don't diminish the findings, but they do remind us that nutrition science is continually evolving.
The Bottom Line
Ashwagandha has become one of the most popular supplements available, and this comprehensive review suggests that many of its most common claims are supported by research.
After reviewing 20 randomized controlled trials involving 1,249 participants, researchers concluded that ashwagandha supplementation significantly improved:
- Memory
- Attention and processing speed
- Executive function
- Muscle strength
- Testosterone levels
At the same time, the review found no meaningful improvements in body weight or body fat percentage, highlighting the importance of separating evidence-based benefits from marketing hype.
Overall, the evidence suggests that ashwagandha may be a useful supplement for healthy adults looking to support cognitive performance, improve recovery, and enhance adaptations to resistance training.
Like any supplement, however, it works best when combined with the fundamentals of good health:
- Regular exercise
- A balanced, nutrient-rich diet
- Quality sleep
- Effective stress management
- Consistent healthy habits
Supplements should complement these lifestyle factors—not replace them.
Simply Good Tip
If you're considering trying ashwagandha, consistency appears to matter more than timing.
The studies showing the greatest benefits most commonly used 600 mg per day for approximately eight weeks. Choosing a standardized extract from a reputable manufacturer can help ensure you're using a product similar to those evaluated in clinical research.
References
- Ashwagandha Supplementation Improves Cognitive Function and Physical Performance in Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Frontiers in Pharmacology.
- Lopresti AL, Smith SJ, Malvi H, Kodgule R. An investigation into the stress-relieving and pharmacological actions of an ashwagandha extract. (Referenced within the review.)
- Wankhede S, Langade D, Joshi K, et al. Examining the effect of Withania somnifera supplementation on muscle strength and recovery. (Referenced within the review.)
- International Society of Sports Nutrition. Position Stand: Dietary Supplements and Exercise Performance.
Frequently Asked Questions
What is ashwagandha?
Ashwagandha (Withania somnifera) is a medicinal plant traditionally used in Ayurvedic medicine. Modern research has investigated its effects on stress, cognitive function, muscle performance, sleep, and hormone regulation.
Does ashwagandha improve memory?
According to this meta-analysis, yes. Researchers found significant improvements in memory, attention, processing speed, and executive function across multiple randomized controlled trials.
Does ashwagandha increase testosterone?
The review found a modest but statistically significant increase in testosterone levels compared with placebo. The effect was supportive—not dramatic—and should not be compared to hormone therapy or anabolic steroids.
Can ashwagandha help build muscle?
Ashwagandha significantly improved muscle strength, particularly in physically active individuals. The evidence suggests it may help enhance adaptations to resistance training rather than directly build muscle on its own.
Does ashwagandha help with weight loss?
Based on this review, no. Researchers found no significant improvements in body weight or body fat percentage compared with placebo.
