Urolithin A

Last reviewed October 2026 · Based on 8 studies

Bottom line

Small trials suggest urolithin A may modestly help muscle strength and endurance, especially in middle-aged and older adults. The evidence is limited: the walking-test result was not significant when pooled, and most trials were run by the company that sells it. Trials ran for four months at most, and no data were found on pregnancy, medicine interactions or upper limits.

What it helps with

Builds muscle strength and endurance — Mixed results, evidence grade C (Limited). Several small placebo-controlled trials and a 2026 review of five trials (236 people); results mixed and the main outcomes not significant; downgraded for inconsistency and small total sample.
Improves walking distance — Mixed results, evidence grade C (Limited). Pooled from two small trials; not statistically significant and low certainty; downgraded for small sample and inconsistency.
Improves mitochondrial health — Mixed results, evidence grade C (Limited). Blood and muscle markers of mitochondrial health only; the energy-production measure did not change in one trial; surrogate outcomes; downgraded for surrogate outcome and inconsistency.
Supports immune health with age — Benefit, evidence grade C (Limited). One small trial of 50 people measuring immune cell markers, not illness; company-sponsored; downgraded for surrogate outcome and small sample.
Helps the heart in heart failure — No effect, evidence grade C (Limited). Crossover trial of 10 patients; no change in echocardiogram measures; small sample and surrogate measures.
Improves blood vessel function — No effect, evidence grade C (Limited). Single trial of 50 adults with obesity; main artery measure unchanged; surrogate outcome.

What it is

Urolithin A is a compound that gut bacteria make after people eat ellagitannin-rich foods [1]. It is sold as a supplement, typically at 500 mg to 1,000 mg a day in trials [2][3].

How it might work

Proposed: urolithin A switches on mitophagy, the clearing of damaged mitochondria. This may help muscle cells keep healthier mitochondria as people age [2]. Animal studies suggest it improves muscle function in older animals, but this is not yet shown in people [2].

What the research says

The strongest positive results are small trials of muscle strength and endurance. In 66 adults aged 65 to 90, endurance in two muscles rose more than with placebo after two months [2]. In 20 resistance-trained men, 1 g a day for eight weeks improved a strength test and repetitions to failure more than placebo [4]. A trial in middle-aged adults reported muscle strength about 12% higher with the supplement [5].

The evidence is weaker for walking and aerobic fitness. Pooling two trials gave about 17 metres more in six minutes, with a range that included zero [6]. A 2026 review of five trials called the wider muscle results exploratory [6].

Other results were mixed or null. In 42 distance runners, the supplement did not improve 3,000-metre time [1]. In 50 middle-aged adults, it changed immune cell types but did not change illness [7].

Doses used in studies

Trials used 1,000 mg a day for four months in older adults [2], 1,000 mg a day for four weeks in runners and in adults with obesity [1][8], 1 g a day for eight weeks in resistance-trained men [4], and 500 mg twice a day for four weeks in people with heart failure [3].

Safety and interactions

In the largest trial in older adults, adverse events were recorded and did not differ between urolithin A and placebo [2]. A trial in adults with obesity described it as well tolerated and feasible [8]. No trial in this review ran longer than four months [2][5]. No data were found on upper intake limits, interactions with medicines, pregnancy or breastfeeding, or kidney, liver or bleeding conditions.

Caveats and open questions

Several trials were sponsored or run by Amazentis, and several of its employees are authors or patent holders [2][5][1]. Trial groups were small, and the 2026 review rated the evidence low certainty [6]. Heart and blood vessel trials found no benefit in small groups [3][8]. Longer, independent trials in well-defined groups are needed [6].