Urolithin A, VO2 Max & Endurance: What to Know

Endurance athletes are drawn to urolithin A for an obvious reason: its whole mechanism centers on the mitochondria, and mitochondria are where aerobic performance ultimately lives. But the honest picture is more nuanced than the headlines. Here is what the human evidence supports, what it does not, and how to think about urolithin A if VO2 max is on your mind.

Why mitochondria and VO2 max are connected

VO2 max is the maximum rate at which your body can take in, transport and use oxygen during hard exercise. It is shaped by two broad systems working in series. The first is oxygen delivery: how much oxygen-rich blood your heart and circulation can push to working muscle, which depends heavily on cardiac output and blood oxygen-carrying capacity. The second is oxygen utilization: how effectively the muscle itself extracts and burns that oxygen, which is governed in large part by mitochondrial density and oxidative capacity within the muscle fibers.

Urolithin A sits squarely in that second system. It does not act on your heart's pumping capacity or your blood. It is studied for supporting the quality of the muscle's mitochondrial machinery through mitophagy, the recycling of worn-out mitochondria so healthier ones can take over. That is a plausible reason for endurance athletes to be curious. It is also the reason to be precise, because central delivery factors like cardiac output are usually the dominant limiter of VO2 max in trained people, and those are not what urolithin A addresses.

The mechanism, in one paragraph

Urolithin A is a gut postbiotic made when gut bacteria break down the ellagitannins in pomegranate, walnuts and berries, and only some people's microbiomes convert it efficiently. Its defining action is to support mitophagy. Endurance training itself is one of the most powerful natural triggers of mitochondrial biogenesis and turnover, so the interest in urolithin A is whether supporting the recycling arm of that turnover can complement what training already does. You can read the full mechanism in our complete urolithin A guide and in our explainer on what mitophagy is.

What the human evidence actually shows

This is the part that deserves care, because it is easy to overstate. Let us organize it by strength.

Human trials (strongest first)

Andreux and colleagues (2019, Nature Metabolism) established in a first-in-human study that urolithin A was safe and well tolerated up to 1,000 mg per day and produced a mitochondrial gene-expression signature in older adults. Liu, D'Amico and colleagues (2022, JAMA Network Open) studied older adults over roughly four months and reported improvements in muscle endurance, measured as the number of muscle contractions before fatigue, a fatigue-resistance outcome relevant to endurance work. Singh and colleagues (2022, Cell Reports Medicine) studied middle-aged adults with 500 mg and 1,000 mg arms and reported benefits for muscle strength and aspects of exercise performance. An 8-week randomized trial in resistance-trained men (Journal of the International Society of Sports Nutrition, 2024) examined endurance and recovery markers in a trained population. A 2025 trial in distance runners extended this line of work into a specifically endurance-trained group. And a 2025 Nature Aging randomized trial found urolithin A supported the mitochondrial health of immune cells in midlife adults over about 28 days, relevant to the recovery and inflammation side of training.

Preclinical evidence (animal and cell studies, not human proof)

The foundational study by Ryu and colleagues (2016, Nature Medicine) showed that urolithin A induced mitophagy, extended lifespan in C. elegans and improved muscle function in rodents. This is where the muscle and endurance hypotheses originated, but rodent running performance is not the same as a demonstrated human VO2 max effect.

The honest limitation on VO2 max specifically

Here is the part most pages skip. The human urolithin A trials have largely measured muscle endurance, strength and fatigue-resistance outcomes, not a clean, repeated demonstration of increased VO2 max as the primary endpoint. Muscle fatigue-resistance and maximal oxygen uptake are related but not identical, and improving one does not automatically move the other, especially since VO2 max in trained athletes is often capped by central oxygen delivery rather than by peripheral muscle mitochondria. A 2024 systematic review in Ageing Research Reviews fairly summed up the field as emerging evidence from short trials of modest size. So the accurate statement is this: urolithin A has human data supporting muscle endurance and performance-related outcomes, and a clear mitochondrial mechanism, but direct evidence that it raises VO2 max as such is limited. Treat any claim of a guaranteed VO2 max increase with skepticism.

Practical guidance for endurance athletes

If you decide urolithin A fits your program, treat it as a supporting player around the things that actually drive aerobic capacity. Consistent aerobic training, adequate protein and total energy, sleep, and progressive overload remain the foundation; no supplement substitutes for them. Urolithin A is studied in the 500 to 1,000 mg per day range, and it appears best thought of as something taken consistently over months rather than as a pre-workout you feel acutely, since the trials ran for weeks to months. You can read more in our notes on urolithin A dosage, how long it takes to work, and urolithin A for muscle. Endurance performance and cardiovascular fitness are health topics, and supplementation is not a treatment for any condition; if you have a heart condition or are building a serious training plan, involve your doctor and, ideally, a qualified coach.

Who might find it most relevant

The strongest human signals so far come from older and middle-aged adults, populations in whom mitochondrial quality and muscle endurance tend to decline with age. That makes urolithin A particularly interesting for masters athletes and anyone returning to endurance training later in life, where supporting the muscle's mitochondrial maintenance has a clear rationale. For younger elite athletes already at a high training volume, the case is more speculative, because their muscle mitochondrial capacity is often already well developed and their VO2 max ceiling is more likely set centrally.

Comparing formats and doses? Our roundup of the best urolithin A gummies lays out what to look for.

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This guide is educational and is not a substitute for advice from a qualified healthcare provider.