Urolithin A and Mitochondrial DNA: What the Science Says

Most people know they inherited their DNA from both parents. Fewer know that a small, second genome sits inside their mitochondria — came almost entirely from their mother — and is unusually exposed to wear and tear. This mitochondrial DNA plays a central role in cellular energy and in the biology of aging. Here is how it works, why it is vulnerable, and where urolithin A does and does not fit.

What is mitochondrial DNA?

Your cells carry two separate sets of genetic material. The large one lives in the nucleus and holds roughly 20,000 protein-coding genes — the blueprint most people mean when they say "DNA." The second, much smaller one lives inside the mitochondria, the structures that generate most of your cellular energy. This is mitochondrial DNA, or mtDNA.

mtDNA is a tiny circular loop containing just 37 genes. Thirteen of those genes code for proteins that are essential parts of the electron transport chain — the assembly line that produces ATP, the cell's energy currency. The rest help the mitochondria manufacture those proteins. So although mtDNA is small, it is not trivial: it builds core components of the machinery that keeps you powered.

Two features make mtDNA distinctive. First, it is inherited almost entirely from your mother, which is why maternal lineages can be traced through it. Second, there are many copies — each cell contains hundreds to thousands of mitochondria, and each mitochondrion carries several copies of the genome. A single cell can therefore hold thousands of mtDNA copies, a redundancy that turns out to matter a great deal.

Why mitochondrial DNA is so vulnerable

mtDNA sits in a demanding neighborhood. It is located right next to the electron transport chain, which is the cell's main source of reactive oxygen species — the reactive by-products of energy production. Being so close to that source means mtDNA is continually exposed to oxidative stress.

On top of that exposure, mtDNA has fewer defenses than nuclear DNA. Nuclear DNA is wrapped around protective proteins called histones and is served by an extensive toolkit of repair enzymes. Mitochondrial DNA is more exposed, with a more limited repair capacity. The combination — high damage exposure, lighter protection — means mtDNA tends to accumulate changes over time.

When a cell contains a mixture of normal and altered mtDNA, biologists call that state heteroplasmy. Thanks to all those redundant copies, a cell can tolerate a surprising amount of damaged mtDNA before function suffers; problems tend to appear only once the proportion of faulty copies crosses a threshold. The gradual rise in mtDNA damage and heteroplasmy with age is considered one of the hallmarks of aging, and it is closely tied to the decline in mitochondrial health seen over a lifetime.

How cells protect their mitochondrial DNA

Cells are not passive in the face of this wear. They run a continuous quality-control program with several layers. Fission and fusion let mitochondria split apart and merge, which helps isolate damaged segments and share healthy contents — our page on mitochondrial fission and fusion goes deeper. Mitochondrial biogenesis, covered in this guide, produces fresh mitochondria to expand the pool.

The step most relevant here is mitophagy: the targeted recycling of mitochondria that have become too damaged to repair. When a mitochondrion is failing — including when it carries too much damaged mtDNA — mitophagy tags it for breakdown, and its components are recycled. In effect, mitophagy is how a cell keeps the overall quality of its mitochondrial population high by removing the worst performers so that healthier ones, built with intact mtDNA, make up more of the pool. If this is new to you, start with our explainer on what mitophagy is.

This is the crucial link: mitophagy does not edit or repair the genome inside a damaged mitochondrion. Instead, it removes the whole underperforming unit. Maintaining responsive mitophagy is therefore one of the ways cells manage the burden of accumulated mtDNA damage — not by fixing individual copies, but by renewing the fleet.

Where urolithin A comes in

Urolithin A is a compound your gut bacteria can produce from ellagitannins found in foods such as pomegranates, walnuts, and certain berries — though many people produce little or none, which is covered in our urolithin A guide. Its best-studied property is supporting mitophagy.

The foundational mechanism work is preclinical: Ryu and colleagues (2016, Nature Medicine) showed that urolithin A induced mitophagy and improved mitochondrial and muscle function in worms and rodents. Because that work was done in animals and cells, it should be read as showing how the compound behaves in model systems, not as proof of outcomes in people.

The human research is more limited but growing. Andreux and colleagues (2019, Nature Metabolism) ran the first-in-human study, reporting that urolithin A was safe and well tolerated up to 1,000 mg per day and shifted a mitochondrial gene-expression signature in older adults. A 2025 randomized, placebo-controlled trial in Nature Aging reported support for mitochondrial health in immune cells in midlife adults over roughly four weeks. Singh and colleagues (2022, Cell Reports Medicine) and Liu, D'Amico and colleagues (2022, JAMA Network Open) studied muscle endurance, strength, and performance over about four months at 500 to 1,000 mg per day.

An important limit, stated plainly

Here is what the evidence does not show. No human trial has demonstrated that urolithin A reduces the burden of mtDNA mutations, reverses heteroplasmy, or repairs mitochondrial DNA. The honest description is narrower and more defensible: urolithin A is studied for supporting the mitophagy pathway that cells use to clear damaged mitochondria, and in human trials it has shown effects on mitochondrial gene-expression signatures and measures of muscle and cellular function. Framing it as a way to "fix your mitochondrial DNA" would overstate the science. We would rather you understand the real mechanism than oversell it.

Practical takeaways for mitochondrial quality

Supporting the systems that maintain mtDNA quality comes down to familiar fundamentals. Regular exercise, especially a mix of endurance and resistance work, is one of the most powerful known stimulators of both mitophagy and mitochondrial biogenesis — see exercise and mitochondrial health. Adequate sleep, a whole-food diet rich in polyphenols, not smoking, and limiting excess alcohol all reduce the oxidative load that damages mtDNA in the first place. A studied mitophagy-supporting compound such as urolithin A can be one part of that broader picture, alongside — not instead of — those basics.

*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.