Ashwagandha and Cortisol: Does It Lower Stress and Boost Strength in the Gym?

Ashwagandha for lifting is one of the few herbal ideas with actual resistance-training trials behind it. Those trials favour ashwagandha over placebo for strength, and larger reviews find it lowers perceived stress and cortisol. The catch is that the studies are small and short, and several authors have supplement-industry ties, so the honest answer is “maybe a modest edge, if the basics are already in place.”

This article sits under our carbs, fats and hydration performance guide. It covers what the trials found, what a realistic dose looks like, and who should leave it alone.

What is ashwagandha and why do lifters care about cortisol?

Ashwagandha (Withania somnifera) is a root used in Ayurveda for centuries. In supplements it is sold as a standardised extract, usually graded by withanolide content. Brands like KSM-66 (root extract) and Sensoril (root and leaf, aqueous) are common names you will see on Indian and global labels.

Lifters care because cortisol is the stress hormone. The popular story is that high cortisol wrecks recovery and muscle growth, so lowering it should help. That story is oversimplified. Cortisol rises acutely during hard training and that is normal. We break down the nuance in cortisol and resistance training: acute vs chronic. Ashwagandha is interesting mainly because chronic psychological stress is a different problem, and it is the one this herb has been tested on.

Does ashwagandha lower cortisol and stress?

This is where the evidence is strongest. A 2024 meta-analysis pooled 9 randomized trials with 558 people and found significantly lower Perceived Stress Scale scores, Hamilton Anxiety Scale scores and serum cortisol with ashwagandha than with placebo. Four of those trials reported mild to moderate adverse events, and the authors said long-term safety information was still needed (Arumugam et al., 2024).

A single trial gives some mechanism. In a 60-day study, 60 stressed adults took 240 mg of a standardised extract or placebo. The ashwagandha group had a larger fall in morning cortisol and in DHEA-S, plus a statistically significant drop in Hamilton anxiety scores. The authors suggest an effect through the hypothalamic-pituitary-adrenal axis, and note that larger and more varied samples are needed (Lopresti et al., 2019).

Two cautions. First, most participants were stressed adults, not lifters, so we cannot assume the same cortisol change in someone who sleeps well. Second, you may see claims of “15-28% cortisol reduction” online. Different trials use different assays and extracts, and I could not confirm a single reliable percentage from the abstracts I read, so I will not quote one.

Does ashwagandha improve strength and muscle size?

Two small trials are the ones people usually cite.

Wankhede et al. (2015) randomized 57 men aged 18-50 with little resistance-training experience to 300 mg of root extract twice daily or a starch placebo for 8 weeks. Bench press 1RM rose 46.0 kg in the ashwagandha group versus 26.4 kg on placebo, leg extension 14.5 versus 9.8 kg, arm muscle area 8.6 versus 5.3 cm2, and chest girth 3.3 versus 1.4 cm. Testosterone and creatine kinase also differed in favour of ashwagandha (Wankhede et al., 2015).

Ziegenfuss et al. (2018, the STAR trial) used 38 recreationally active men and 500 mg a day of the aqueous extract Sensoril for 12 weeks on a 4-day split. 1RM squat rose 19.1 versus 10.0 kg and bench 12.8 versus 8.0 kg, and the ashwagandha group alone showed significant gains in some power, time-trial and perceived recovery measures. No other body-composition differences were found, apart from a more favourable android/gynoid ratio (Ziegenfuss et al., 2018).

Those are encouraging numbers. They are also the reason to slow down.

How strong is the evidence for ashwagandha strength gains?

Weaker than the headlines. A 2026 systematic review and meta-analysis limited to structured resistance training found four eligible RCTs, three of which (161 people) could be pooled. The pooled effects favoured ashwagandha for bench press 1RM (SMD 0.60, 95% CI 0.20-1.01), lower-body 1RM (0.52) and chest circumference (0.86), but not body fat. Under a more conservative statistical adjustment both strength estimates lost significance, each depended on one influential trial, and certainty was rated low (very low for chest circumference). The authors concluded that current evidence does not establish a meaningful boost to training adaptations (Lee et al., 2026).

Why the disagreement between “significant trial” and “fragile meta-analysis”? Small samples, short durations, trainees who were relatively new or recreational (so almost any added stimulus can look big), and some risk-of-bias concerns. A 2021 Bayesian meta-analysis was more optimistic about physical performance, but it also called for more comparable studies in trained and athletic groups (Bonilla et al., 2021).

How much ashwagandha should I take? KSM-66 dosage and extract choice

The gym trials used 600 mg a day split into two 300 mg doses (root extract) and 500 mg a day (aqueous extract). A dose-response meta-analysis for stress suggested a benefit in the 300-600 mg a day range, with low certainty (Akhgarjand et al., 2022). In practice, a dose on that standardised-extract range is where the evidence sits.

On “ksm 66 dosage muscle growth”: no trial I found compared KSM-66 with other extracts in lifters, so I cannot say it is better. Choose a standardised root extract with a stated withanolide percentage. Because the Indian supplement market has many look-alike products, also read how to spot fake or underdosed supplements and what third-party certifications mean. For a head-to-head on extracts and cycling, see our KSM-66 vs Sensoril guide.

Question	What the trials used	Confidence
Daily dose	300-600 mg standardised extract	Low for stress, low for strength
Duration	8-12 weeks (cortisol study: 60 days)	Short-term only
Timing	Once or twice daily, no clear winner	Low
Cycling	Not tested	Unknown

Is it safe? Side effects, liver risk and who should skip

Most healthy adults tolerated it in trials. A 2026 review of 23 trials (2,317 participants, 125-600 mg a day, up to 180 days) found liver, kidney, blood, hormone and cardiovascular markers stayed within normal ranges, and mild effects such as stomach upset, headache and drowsiness occurred in both groups. It also stressed that long-term data beyond 180 days is limited (Coope et al., 2026). Note that some authors have supplement-industry ties.

Case reports tell a different side of the story. A multi-centre Indian case series described cholestatic hepatitis from single-ingredient ashwagandha products, Of the 8 patients, 5 had underlying chronic liver disease, and 3 of them developed acute-on-chronic liver failure and died. In the others the injury was prolonged but resolved (Philips et al., 2023). Chemical analysis found no adulteration or contamination, so this was not simply a dodgy batch. A case series cannot tell you how common this is, but it is why anyone with liver disease should avoid ashwagandha unless their doctor says otherwise.

On the thyroid, a small trial in 50 people with subclinical hypothyroidism found ashwagandha changed TSH, T3 and T4 compared with placebo (Sharma et al., 2018). That is a reason to talk to your doctor if you have a thyroid condition or take thyroid medicine, not a reason to self-treat.

Stop and get medical advice if you develop jaundice, dark urine, severe itching or persistent nausea. Pregnant or breastfeeding, have liver or thyroid disease, or take prescription medicines? Check with your doctor before starting. You may also hear about “anhedonia” or emotional flatness. I could not find this as a measured outcome in the trials I reviewed, so treat it as anecdotal, but stop if your mood changes.

What should realistic expectations look like?

Think small and slow. Even the best-case trials showed modest differences over 8-12 weeks, mostly in newer lifters. Do not expect cortisol to “reset” or your bench to jump 20 kg.

If you try it, run it like an experiment:

1. Sort sleep, protein (see our protein calculator) and a progressive plan such as the free training plans.
2. Start one product at a time, with third-party testing.
3. Use 300-600 mg a day of standardised extract for 8-12 weeks.
4. Track sleep, perceived stress and your key lifts.
5. If nothing changes, stop. Money is better spent on food.

Ashwagandha belongs in the lower tiers of the supplement hierarchy, well below creatine and protein, and it is only one of the adaptogens like rhodiola. If stress is the real problem, read about psychological stress and muscle repair, and consider changing life, not just capsules.

Bottom line

Ashwagandha probably does lower perceived stress and cortisol, and small trials suggest a modest strength edge in newer lifters. The evidence is low-certainty, the long-term data is thin, and reported liver injury cases mean it is not risk-free. Sleep, food and progressive training stay first. If you try it, use a tested standardised extract, set an 8-12 week window, and see a doctor first if any of the cautions apply to you.