Urolithin A

For most people, eat pomegranate, berries and walnuts instead. No trial has yet shown the pill helps older adults, including those losing muscle, so it is an optional experiment at most — never a substitute for strength training and enough protein.

What it is

Urolithin A is a postbiotic: a compound made by gut bacteria from ellagitannins, plant polyphenols found in pomegranate, berries and walnuts. It is the clearest dietary activator of mitophagy, the housekeeping process that tags and recycles damaged mitochondria, the cell's power plants. That mechanism is why it is sold for muscle strength and healthy aging. The wider category of anti-aging compounds is compared on Geroprotectors.

The largest trial: some strength, main goal missed

The ATLAS trial gave urolithin A or placebo to 88 overweight middle-aged adults for four months.^[1]

• Hamstring strength rose about 10–12% on urolithin A while it fell about 10% on placebo.
• Front-of-thigh (quadriceps) strength did not change significantly.
• Inflammation. The marker C-reactive protein (CRP) fell, significantly only at the higher 1,000 mg dose.
• Fitness. Peak oxygen uptake (VO₂) rose about 10% in that higher-dose group, but fell just short of significance against placebo.
• The primary endpoint, peak power, was missed.

In older adults, both main goals were missed

A second randomised trial gave urolithin A or placebo to 66 adults aged 65–90. It missed both of its primary endpoints: there was no improvement in six-minute walk distance or in maximal ATP production — the most adenosine triphosphate (ATP), the cell's energy currency, that the muscle's mitochondria can make.^[2] It did show a muscle-endurance signal at two months, but that had gone by four months as the placebo group caught up. The two trials have not been reconciled. No trial has tested the pill against strength or function in people with age-related muscle loss. The only one in frail older adults, run by the maker in 26 people aged 65–85, measured mitochondrial structure under the microscope instead; it finished in April 2025 and had reported no results by October 2026.^[3]

Across all the trials, the picture thins out

A systematic review of five randomised trials in 236 participants could pool only a single outcome, and that one was inconclusive and rated low certainty.^[4]

Most trials, including the largest, were funded by the maker (Amazentis). The few small trials without declared industry ties are mixed,^{[5] [6]} and none studied hard outcomes such as falls, fractures or survival. In 42 highly trained male distance runners, four weeks of urolithin A did not improve running performance.^[7] Two four-week trials in 50 middle-aged adults each looked beyond muscle and split the same way: a maker-funded one in healthy adults met its main goal of shifting immune cells toward a younger-looking profile,^[8] while an independent one in adults with obesity found no improvement in artery function.^[9]

Do you make it yourself?

Whether you produce urolithin A from food depends on your gut bacteria. Roughly 1 in 10 people make none at all from dietary ellagitannins, according to the Spanish group that has mapped these gut-bacteria patterns in people aged 5 to 90 and found age the main thing shaping them; the amount everyone else makes varies widely.^{[10] [11]}

The often-quoted figure that only about 40% of people convert comes from a study funded by the Mitopure maker, after a single glass of pomegranate juice.^[12]

What to do

1. Eat the foods. Pomegranate, berries and walnuts are the cheaper bet for most people.
2. If you are losing muscle with age, start with what works: resistance training two to three times a week and enough protein. Urolithin A has not been shown to help on top of that.
3. If you try the pill anyway, treat it as a short experiment. A first four-week trial in healthy, sedentary older adults found it safe.^[13]
4. Keep expectations modest. The best trial found a gain in one muscle group, not the main outcome it was designed to measure.

Further reading

• Singh A et al. Urolithin A improves muscle strength, exercise performance, and biomarkers of mitochondrial health in a randomized trial in middle-aged adults. Cell Rep Med 2022.^[14]
• Liu S et al. Effect of Urolithin A Supplementation on Muscle Endurance and Mitochondrial Health in Older Adults: A Randomized Clinical Trial. JAMA Netw Open 2022 — missed both primary endpoints.^[15]
• Andreux PA et al. The mitophagy activator urolithin A is safe and induces a molecular signature of improved mitochondrial and cellular health in humans. Nat Metab 2019 — first-in-human safety trial.^[16]
• Dao T et al. Effects of Urolithin A supplementation on muscle health outcomes in humans from randomized controlled trials. Front Nutr 2026.^[17]
• Cortés-Martín A et al. The gut microbiota urolithin metabotypes revisited: the human metabolism of ellagic acid is mainly determined by aging. Food Funct 2018.^[18]