Urolithin A for Men Over 40: What the Mitophagy Trials Actually Show About Muscle, Energy and Aging

Urolithin A is a compound made by gut bacteria from ellagitannins in pomegranates, walnuts and berries. Urolithin A switches on mitophagy, the process cells use to clear out damaged mitochondria, which slows with age. Human trials in middle-aged and older adults using 500 to 1,000 mg per day have reported better muscle endurance and strength and improved mitochondrial markers. This guide covers the trial data, dosing, food sources and the open questions.

Urolithin A is a small molecule produced by gut bacteria when they break down ellagitannins and ellagic acid, polyphenols found in pomegranates, walnuts, pecans, raspberries and strawberries. Once absorbed, urolithin A activates mitophagy, the cellular cleanup process that tags damaged mitochondria and breaks them down so healthier ones can replace them. Mitophagy becomes less efficient with age, and worn-out mitochondria pile up in muscle, which is one reason men lose endurance and strength after 40.

The catch is that many adults do not have the right gut bacteria to turn pomegranate or walnut polyphenols into meaningful amounts of urolithin A. That finding pushed researchers to test urolithin A directly as a supplement. Since 2019, three randomized human trials have reported results, which puts urolithin A ahead of most longevity compounds that have only mouse data behind them.

Urolithin A is a postbiotic, meaning a compound the gut microbiome makes from something in the diet. Ellagitannins in foods are too large to be absorbed well. Bacteria in the colon, including species from the Gordonibacter and Ellagibacter groups, convert them step by step into urolithins, and urolithin A is the main end product in people who have the right microbes.

Researchers at CEBAS-CSIC in Spain, led by Francisco Tomás-Barberán and Juan Carlos Espín, grouped people into three urolithin metabotypes. Metabotype A produces mainly urolithin A. Metabotype B produces urolithin A plus isourolithin A and urolithin B. Metabotype 0 produces almost none. Metabotype B and metabotype 0 become more common with obesity and metabolic syndrome, so the men who might gain the most from urolithin A are often the least able to make it.

Pomegranate juice illustrates the problem. In studies where volunteers drank the same serving of pomegranate juice, urinary urolithin A varied by more than 100-fold between people, and a sizable minority produced almost none. Diet alone therefore gives an unpredictable dose. A stool or urine test can show producer status, but these tests are mostly available through research programs and a few direct-to-consumer companies.

Urolithin A works by triggering mitophagy through the PINK1 and Parkin pathway, which marks damaged mitochondria for removal. A 2016 study in Nature Medicine by Dongryeol Ryu, Johan Auwerx and colleagues at EPFL in Switzerland showed that urolithin A extended lifespan in the roundworm C. elegans by about 45 percent and improved running endurance in aged mice by about 42 percent. Those were the results that moved urolithin A into human testing.

Mitochondrial quality in muscle declines steadily with age and inactivity. The line chart below shows the general pattern described in muscle biopsy research: mitochondrial function falls slowly through the 30s and 40s and faster after 60, while regular endurance training keeps it higher at every age. The values are illustrative, not measurements from one study.

Human trials of urolithin A show consistent improvements in mitochondrial and inflammation markers and moderate gains in muscle endurance or strength, but not in every outcome measured. Three published randomized trials form the core of the evidence, all funded by or run with Amazentis, the Swiss company that makes the Mitopure form of urolithin A. That funding does not make the results wrong, but independent replication is still thin.

The first-in-human trial, published by Pénélope Andreux and colleagues in Nature Metabolism in 2019, gave healthy sedentary adults aged 61 to 85 doses of 500 or 1,000 mg daily for 28 days. Urolithin A was well tolerated, reached muscle tissue, raised expression of mitochondrial genes in muscle biopsies and lowered plasma acylcarnitines, a sign that mitochondria were burning fat more completely.

The Singh 2022 trial in Cell Reports Medicine is the most relevant to men over 40. Anurag Singh and colleagues randomized 88 overweight but otherwise healthy adults aged 40 to 65 to placebo, 500 mg or 1,000 mg of urolithin A daily for four months. Hamstring strength rose by about 12 percent with 500 mg and about 10 percent with 1,000 mg compared with placebo, and knee flexion strength improved as well. The 1,000 mg group also showed better peak oxygen uptake and six-minute walk distance, along with lower C-reactive protein, a marker of inflammation.

The Liu 2022 trial in JAMA Network Open, run by Sophia Liu and David Marcinek at the University of Washington, gave 66 adults aged 65 to 90 either 1,000 mg of urolithin A or placebo for four months. Muscle endurance, measured as the number of contractions a hand muscle and a leg muscle could perform before fatigue, improved significantly more with urolithin A. Six-minute walk distance improved in both groups, with no significant difference between them, and plasma acylcarnitines and ceramides fell in the urolithin A group.

More recent work has looked beyond muscle. A 2025 trial in Nature Aging led by Dominic Denk and Florian Greten reported that 1,000 mg of urolithin A daily for four weeks in healthy middle-aged adults increased the share of naive, less exhausted CD8 T cells in blood, a sign of a younger-looking immune profile. The study was short and small, so the immune findings are best treated as an early signal.

Urolithin A has not been shown to raise testosterone in men. No published human trial has used testosterone as an outcome. A handful of rodent and cell studies suggest urolithin A may protect Leydig cells, the testosterone-producing cells in the testes, from oxidative stress, but that is a long way from a measurable effect in a man over 40.

Urolithin A may still matter for men who care about testosterone for indirect reasons. Poor mitochondrial function in muscle goes hand in hand with insulin resistance, higher inflammation and less physical activity, and all three are linked to lower testosterone. Improving muscle endurance and lowering CRP could support the conditions that favor healthy hormone levels, but any effect on testosterone itself remains unproven.

The doses studied in men and women over 40 are 500 mg or 1,000 mg of urolithin A once daily, usually taken with a meal. The Singh 2022 trial found similar strength gains at both doses, while the aerobic and inflammation improvements were clearer at 1,000 mg. A man trying urolithin A would typically start at 500 mg and allow at least two to four months before judging the effect, since that matches the trial timelines.

Eating pomegranates or walnuts cannot reliably substitute for these doses. Even among good producers, a glass of pomegranate juice produces blood levels of urolithin A far lower and more variable than a 500 mg supplement. Food sources are still worth eating for fiber and other polyphenols, and they may help shift the microbiome over time, but they are not a controlled dose.

Urolithin A has a clean safety record in published human trials at doses up to 1,000 mg daily for four months, with side effects no different from placebo. Andreux 2019 tested single doses up to 2,000 mg without serious adverse events. Toxicology work published by Heilman and colleagues in 2017 found no genotoxicity and no adverse effects in rats at very high doses, and the US FDA issued a no-questions letter on the GRAS notice for urolithin A in food products in 2018.

Long-term safety beyond four months has not been studied in large groups. Men taking anticoagulants, chemotherapy or multiple prescription drugs should talk to their doctor first, because urolithin A is metabolized in the liver and its interactions are not well mapped. Product quality also varies. Supplements labeled as pomegranate extract or ellagic acid are not the same as urolithin A, and only the finished compound gives a predictable dose.

A man over 40 can test urolithin A sensibly by measuring a few baseline markers, keeping training and diet stable, and reassessing after about four months. The plan below is an educational framework that mirrors the published trials. It is not medical advice, and any supplement plan should be discussed with a clinician who knows the full medication list.

• Buying pomegranate extract or ellagic acid capsules and expecting the same results as the trials, which used purified urolithin A
• Judging the effect after two weeks when trial benefits took two to four months
• Using urolithin A as a reason to skip lifting, which produces larger strength gains on its own
• Changing training, diet and supplements all at once, which makes it impossible to tell what helped
• Assuming a benefit for testosterone that no human trial has measured

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