Does urolithin A work? If you have seen the $99 strawberry gummies promising to change how your cells age, that is the question to ask before you subscribe. Urolithin A is a postbiotic compound your gut can make from pomegranate, berries and walnuts, and the supplement industry’s pitch rests on one striking number: a randomised trial that reported 39% more mitophagy, the cellular clean-up of damaged mitochondria, in people taking 500 mg a day for four months. The number is real. What it means for your muscles is a more complicated story.

The quotable version: urolithin A reliably engages its biological target, clearing damaged mitochondria in muscle cells, but the evidence that it makes people meaningfully stronger is thin and mixed. The best trial found about 12% better hamstring strength at 500 mg a day, missed its primary performance endpoint, and was funded by the company that sells the supplement. It is an interesting cellular signal, not a proven strength intervention.

What urolithin A is, and why your gut matters more than the bottle

Urolithin A is not a vitamin and not a stimulant. It is a postbiotic: a compound produced when your gut bacteria digest ellagitannins, plant chemicals found in pomegranates, raspberries, strawberries, blackberries and walnuts. Its biological claim to fame is mitophagy, the selective recycling of worn-out mitochondria. Mitochondria are the cell’s energy factories, and their quality declines with age, especially in skeletal muscle. The theory is elegant: clear the broken factories, and the muscle runs cleaner.

There is a catch that makes the supplement pitch land harder. Only some people are efficient urolithin A producers. Researchers describe three gut metabotypes, and your ability to convert pomegranate into urolithin A depends on which microbes you carry. That is the industry’s strongest argument for skipping the fruit and buying the capsule: direct supplementation delivers a known dose regardless of your microbiome. Mitopure, the form used in the trials and the $99 gummies, is a patented, highly pure version of the compound developed by the company Amazentis, now owned by Timeline.

The 39% number: where it actually comes from

The 39% figure made headlines on 16 October 2026, when the New York Post covered Timeline’s Mitopure gummies. According to the reporting, a randomised, double-blind trial published in Cell Reports Medicine found that participants taking 500 mg of Mitopure daily for four months experienced a 39% increase in mitophagy compared with the control group. The product is positioned as the only clinically proven urolithin A gummy shown to improve cellular energy and muscle strength, and it costs $99 for a month’s supply.

That trial is the ATLAS study, published by Singh and colleagues in 2022, and it is worth reading directly rather than through the marketing. The trial randomised 88 middle-aged, overweight, sedentary adults aged 40 to 65 into three groups: placebo, 500 mg of urolithin A daily, or 1,000 mg daily, for four months. Here is what the published paper reports: roughly 12% greater muscle strength, specifically in the hamstrings; reductions in plasma acylcarnitines and C-reactive protein, suggesting better mitochondrial efficiency and less inflammation; and increased expression of proteins linked to mitophagy and mitochondrial metabolism in skeletal muscle biopsies. The authors also describe clinically meaningful improvements in aerobic endurance and six-minute walk performance.

Does urolithin A work for muscle strength? The honest verdict

This is the question the biohacker mindset was built for: does urolithin A work for muscle in a way you would actually notice? Read the ATLAS paper the way a sceptical colleague would, and the 12% figure starts to wobble. Peak power output, the trial’s declared primary endpoint, did not improve significantly. The paper labelled every endpoint exploratory and made no statistical correction for testing many outcomes, which means positive findings could partly be chance.

More importantly, about half of the headline strength gap came from the placebo group getting weaker. Hamstring strength rose 12% on 500 mg and 9.8% on 1,000 mg, while the placebo group lost 9.8%, so the supplement preserved strength as much as it built it. Thigh and grip strength did not differ between groups at all. The aerobic and walking improvements were significant within the high-dose group but not significant when compared against placebo, which is the comparison that actually matters. The muscle biopsies showing the mitophagy signal came from only six people per group, and those results were compared within each group rather than between groups. And the funding line matters: the trial was paid for by Amazentis, the company selling Mitopure.

None of that makes the trial worthless. A 39% mitophagy increase is a genuine cellular finding, and a strength signal that survives in the hamstrings after four months is worth knowing about. But a biohacker reads the whole paper, not the press release. On the current evidence, urolithin A moves the cellular machinery it is supposed to move, and it has a modest, mixed record on the functional outcomes people actually care about.

The older-adults trial tells the same cautionary tale

The second important trial, published by Liu and colleagues in JAMA Network Open in 2022, tested urolithin A in 66 adults aged 65 to 90, all of whom started with below-average capacity to produce ATP, the energy currency mitochondria generate. Participants took 1,000 mg a day for four months. The two co-primary outcomes, six-minute walk distance and maximal ATP production measured by magnetic resonance spectroscopy, showed no significant difference against placebo. Both groups walked further at four months, which is exactly what you would expect from a practice effect rather than a drug effect.

The secondary signals were kinder but still fragile. Muscle endurance in hand and leg muscles improved at two months, but that effect was no longer significant at four months. UW Medicine’s own newsroom release put it plainly: two measures of muscle endurance improved in the supplement group, while two other comparisons did not support the thesis. The sponsor again had a role in the study design and in the decision to publish. If urolithin A were a strong, reliable strength intervention, this is the population where it should have shone. It did not.

What self-experimenters should actually do

So where does that leave an optimiser with a credit card and a curiosity about mitochondrial clean-up? The evidence-backed protocol, if you decide the signal is worth chasing, looks like this. The trials that found anything used 500 to 1,000 mg of Mitopure a day, every day, for four months. Expect nothing before month two; even the brand says strength and cellular renewal build over roughly four months. Track what the trials actually measured: hamstring or leg strength, endurance before fatigue, walking performance. Not the mirror, not how the gummies taste, and not a biological-age clock. If you are a non-producer of urolithin A from food, you are the person most likely to see any benefit, because you are the person with the lowest starting levels.

On safety, the record is genuinely reassuring so far. The first-in-human study, published by Andreux and colleagues in Nature Metabolism in 2019, tested single doses up to 2,000 mg and daily doses up to 1,000 mg for four weeks in healthy elderly volunteers, with no observed side effects and good bioavailability. Across the five completed trials identified in a 2024 systematic review, totalling 250 participants, no serious adverse events were reported. That is a decent safety foundation, but it is still worth discussing any supplement with your doctor, particularly if you take prescription medicines or have an existing condition.

The gummy question deserves its own honest math. The $99-a-month product contains the same active ingredient studied in the trials, and it carries NSF certification with third-party testing for purity and potency. What you are really paying for is convenience and strawberry flavour. The marketing line, that it is the only clinically proven gummy shown to improve cellular energy and muscle strength, goes well beyond what the primary endpoints of the published trials actually showed. If the price makes you wince, the evidence does not currently justify a subscription on strength grounds alone.

For context on how this fits a wider optimisation stack, our breakdown of the creatine-without-exercise trial covers a supplement with a stronger strength record and honest caveats, our longevity supplement guide puts urolithin A in its proper category, and yesterday’s honest read on GLP-1 ageing claims applies the same surrogate-endpoint scepticism to a very different intervention.

Frequently asked questions

The bottom line for optimisers

Does urolithin A work? It works as a mitophagy activator in human muscle, and that is not nothing. It has a thin, mixed record on the strength and performance outcomes that would justify its price, built on industry-funded trials that missed their primary endpoints. Treat it as an interesting experiment, not a proven protocol: track real metrics, give it four months, and keep your scepticism alongside your subscription.

Sources: Singh et al., Cell Reports Medicine, 2022 (ATLAS trial, PMID 35584623, NCT03464500); New York Post reporting on the Mitopure gummy trial, 16 October 2026; Liu et al., JAMA Network Open, 2022 (ENERGIZE trial, PMID 35050355); Andreux et al., Nature Metabolism, 2019 (first-in-human safety); UW Medicine newsroom on the older-adults trial; 2026 systematic review of urolithin A RCTs on muscle health outcomes, Frontiers in Nutrition.