Urolithin A is a compound your body produces when gut bacteria break down ellagitannins, a type of polyphenol found in foods like pomegranates, walnuts, and berries. It has gained significant attention for its ability to trigger a cellular cleanup process called mitophagy, where your body removes damaged mitochondria and replaces them with healthy ones. Only about 40% of people have the right mix of gut bacteria to produce urolithin A naturally, which is one reason it’s now available as a supplement.
How Your Body Makes Urolithin A
Ellagitannins are large polyphenol molecules found in plant foods. They’re poorly absorbed in the upper digestive tract and arrive in the large intestine mostly intact. Once there, specific gut bacteria hydrolyze them into smaller compounds, starting with ellagic acid. From ellagic acid, bacteria in the Eggerthellaceae family (species like Gordonibacter urolithinfaciens and Ellagibacter isourolithinifaciens) perform several metabolic steps to produce an intermediate called urolithin C. A separate group of bacteria, certain Enterocloster species, then converts urolithin C into urolithin A through a final dehydroxylation step.
This multi-step bacterial relay is why not everyone produces urolithin A. Your ability to make it depends entirely on whether your gut microbiome contains the right combination of bacterial species. Some people produce large amounts, others produce none, and diet, geography, and age all influence your microbiome composition. Researchers have also identified Bifidobacterium pseudocatenulatum and Enterococcus faecium as species capable of producing urolithin A from ellagic acid.
Foods That Provide the Raw Ingredients
Since urolithin A isn’t found directly in food, you need to eat foods rich in ellagitannins and hope your gut bacteria do the rest. Pomegranate juice made from the whole fruit (including the rind) contains the highest concentration of ellagitannins of any commonly consumed juice, largely due to a unique compound called punicalagin. Other good sources include black raspberries, red raspberries, strawberries, walnuts, and almonds.
The catch is that eating these foods doesn’t guarantee urolithin A production. If your gut lacks the necessary bacteria, those ellagitannins pass through without being converted into anything particularly useful at the systemic level.
What Mitophagy Does and Why It Matters
Mitochondria are the structures inside your cells that generate energy. Over time, they accumulate damage and become less efficient. Mitophagy is the process by which cells identify these worn-out mitochondria, break them down, and recycle their components to build new, functional ones. Urolithin A activates this process through a signaling pathway involving two proteins (PINK1 and Parkin) that tag damaged mitochondria for removal.
This matters because declining mitochondrial function is one of the recognized hallmarks of aging. As mitophagy slows with age, damaged mitochondria pile up, producing excess reactive oxygen species that contribute to inflammation and cellular damage. By restarting this cleanup process, urolithin A essentially helps cells maintain their energy production capacity.
Effects on Muscle Strength and Endurance
The most robust human evidence for urolithin A comes from its effects on muscle function. In a randomized, placebo-controlled trial of middle-aged adults, participants who took urolithin A daily for four months showed roughly 12% improvement in leg muscle strength. Both the 500 mg and 1,000 mg doses produced statistically significant gains: hamstring strength increased by 12% and 9.8% respectively, while maximum torque during knee flexion improved by about 10.5% in both groups.
Meanwhile, participants in the placebo group actually lost muscle strength over the same period, with average torque declining by 9.8% and maximum torque dropping by 9.3%. This divergence suggests urolithin A doesn’t just build strength in an absolute sense but may protect against the natural muscle decline that occurs with age.
Aerobic capacity also improved. Participants taking 1,000 mg showed statistically significant increases in peak oxygen consumption (VO2) at both the two-month and four-month marks. Physical performance on a six-minute walk test improved as well, though peak power output on a cycling test did not change significantly. A separate trial in older adults also demonstrated improvements in muscle endurance with long-term supplementation.
Immune Function and Inflammation
Aging brings a state of chronic, low-grade inflammation sometimes called “inflammaging,” characterized by elevated levels of inflammatory signaling molecules throughout the body. This persistent inflammation is linked to increased risk of heart disease, cancer, and general immune decline. T cells with dysfunctional mitochondria are central to this problem, as they can trigger widespread inflammatory signaling.
A placebo-controlled trial published in Nature Aging found that urolithin A supplementation expanded a population of naive-like, less exhausted immune cells in participants’ blood, suggesting the immune system was being partially “rejuvenated.” Single-cell gene sequencing revealed that urolithin A shifted gene activity across multiple immune cell types, modulating pathways related to both inflammation and metabolism. These findings point to urolithin A’s potential to counteract the immune deterioration that comes with age.
Cardiovascular and Metabolic Effects
Animal research has shown that urolithin A can reduce blood pressure and reverse vascular remodeling, the process by which blood vessel walls thicken and stiffen under conditions like hypertension. In hypertensive rats, four weeks of urolithin A treatment reduced blood vessel wall thickness, restored narrowed blood vessel diameter, and lowered blood pressure. These effects traced back to urolithin A’s ability to reduce mitochondrial oxidative stress in blood vessel smooth muscle cells, nearly normalizing the elevated levels of reactive oxygen species seen in hypertension.
On the metabolic side, animal studies have found that urolithin A improves insulin sensitivity in mice fed a high-fat diet. It reduced fat accumulation in the liver, shrank enlarged fat cells, decreased inflammatory immune cell infiltration into fat tissue, and boosted mitochondrial production in the liver. These effects occurred independently of the parent compounds found in food, confirming that urolithin A itself, not just ellagitannins, drives the metabolic benefits.
Dosage and Safety
Human trials have used doses ranging from 10 mg to 1,000 mg per day, with study durations spanning 28 days to four months. The muscle strength benefits in clinical trials appeared at both 500 mg and 1,000 mg daily doses. Across five studies involving 250 healthy participants, urolithin A showed dose-dependent anti-inflammatory effects and upregulated genes involved in mitochondrial function, autophagy, and fat metabolism.
Safety data has been reassuring. In a study of elderly participants receiving single and multiple oral doses, the primary safety endpoint was met with no serious adverse effects and no product-related non-serious adverse effects recorded. A full battery of safety tests, including vital signs, ECG, blood chemistry, and urinalysis, showed no clinically significant changes. Urolithin A is sold commercially as a supplement (under the brand name Mitopure, among others) and has been well tolerated across all published human trials.
The 60% Problem
The biggest limitation of relying on food sources for urolithin A is that roughly 60% of people cannot produce it efficiently, or at all, from dietary ellagitannins. This is purely a function of gut microbiome composition, and there’s currently no simple way to shift your microbiome to become a urolithin A producer. Direct supplementation bypasses this bottleneck entirely, delivering urolithin A regardless of your gut bacteria profile. For people who do produce it naturally, the amount generated from food varies widely and is difficult to quantify or control.