What Are Mitochondria?
You have probably heard mitochondria called the powerhouse of the cell. It is a good nickname, but it undersells them. Mitochondria are tiny structures inside almost every cell in your body, and they do far more than make energy. Here is a clear, general-audience tour of what they are, what they do, and why they matter as you age.
The short answer
Mitochondria are small compartments, called organelles, found inside your cells. Their headline job is to produce ATP, the molecule your cells spend to power nearly every task, from contracting a muscle to firing a nerve to building new proteins. A typical cell can hold anywhere from a few hundred to several thousand mitochondria, and the busiest tissues have the most. Your heart, which never rests, and your leg muscles, which do heavy work, are especially dense with them. In a very real sense, the phrase powerhouse of the cell is accurate: mitochondria are where most of your usable energy is generated.
What they actually look like
Under a microscope, mitochondria look like small beans or threads, and they are surrounded by two membranes rather than one. The outer membrane is smooth. The inner membrane is dramatically folded into pleats called cristae, and those folds are where the energy-making machinery is packed. The more folded surface a mitochondrion has, the more energy machinery it can run. Mitochondria are not fixed in place or in number, either; they constantly move, split apart, and fuse together in a dynamic network, and cells can build more of them when demand rises, such as with regular exercise training.
How they make energy
Mitochondria carry out the most productive stages of cellular respiration, the process that converts food and oxygen into ATP. Nutrients from your food are broken down into smaller molecules, which are fed into a series of reactions inside the mitochondrion. The final and largest step, called oxidative phosphorylation, takes place on those folded inner membranes: electrons are passed down a chain of proteins, their energy is used to build a proton gradient, and a molecular turbine called ATP synthase spins to manufacture ATP. Oxygen is consumed at the end of this line, which is ultimately why you breathe. If you want the mechanics, our companion explainers cover cellular respiration and oxidative phosphorylation in detail.
They do more than energy
Calling mitochondria mere powerhouses hides how much else they handle. They help regulate the balance of calcium inside cells, which matters for signaling. They contribute to producing certain hormones and to managing metabolism. And, strikingly, they play a central role in deciding when a damaged cell should undergo programmed cell death, a controlled process that clears out cells the body no longer needs. Mitochondria even carry their own small loop of DNA, separate from the DNA in the cell's nucleus, a clue that they descend from ancient bacteria that were absorbed into early cells more than a billion years ago. That evolutionary origin is why they behave a little like semi-independent residents inside your cells.
Why mitochondria change with age
Mitochondria take wear over time. Because they handle high-energy electrons and oxygen, a small share of those electrons escape and form reactive molecules that can damage mitochondrial membranes and proteins. Over many years, some mitochondria accumulate enough damage that they work less cleanly. Healthy cells manage this with a two-part strategy: they recycle their most worn-out mitochondria through a process called mitophagy, and they build fresh ones to replace them. When this housekeeping keeps pace, the mitochondrial network stays in good shape. Our explainer on what mitophagy is unpacks this recycling routine step by step.
Where urolithin A comes in
Urolithin A has become a focus of mitochondrial research because of its studied link to mitophagy. It is a postbiotic, meaning your gut bacteria can produce it, in this case from ellagitannins found in pomegranates, walnuts, and certain berries. There is a catch that surprises many people: only some individuals carry the specific gut microbes needed to make meaningful amounts of urolithin A from those foods, which is part of the rationale for supplementing it directly.
What does the human evidence show? A first-in-human trial (Andreux and colleagues, Nature Metabolism, 2019) found urolithin A safe and well tolerated at doses up to 1,000 mg per day and reported a mitochondrial gene-expression signature. Randomized human trials have since reported effects on muscle endurance in older adults (D'Amico and colleagues, JAMA Network Open, 2022) and on muscle strength and exercise performance in middle-aged adults, tested at 500 and 1,000 mg (Singh and colleagues, Cell Reports Medicine, 2022). A 2025 randomized trial in Nature Aging reported support for immune-cell mitochondrial health in midlife adults. The specific mechanism, that urolithin A promotes mitophagy, was first established in preclinical laboratory and animal research (Ryu and colleagues, Nature Medicine, 2016), which explored mitophagy, lifespan in a worm model, and muscle in rodents; this is preclinical and should be read as such. A 2024 systematic review in Ageing Research Reviews concluded the human evidence is still emerging. In supplements, doses of 500 to 1,000 mg per day have been studied, with 1,000 mg at the top of that range.
Supporting your mitochondria day to day
You cannot micromanage your mitochondria, but the habits that support them are refreshingly ordinary. Regular aerobic and resistance exercise is the most reliable way to prompt the body to build more mitochondria and maintain their folded membranes. Adequate sleep, a diet with enough protein and a range of micronutrients, and not smoking all help. Supplements such as SOMA HEALTH Urolithin A Gummies are intended to complement those fundamentals rather than replace them. If you are dealing with ongoing fatigue, weakness, or exercise intolerance, those symptoms can stem from many causes and are worth raising with a qualified healthcare provider rather than self-diagnosing.
Frequently asked questions
What is the main job of mitochondria?
Their headline job is producing ATP, the molecule cells spend for energy, through cellular respiration. But they also help regulate calcium, contribute to metabolism and certain hormones, and play a role in programmed cell death.
Why are mitochondria called the powerhouse of the cell?
Because they generate most of the cell's usable energy in the form of ATP. The nickname captures their biggest role, even though they do considerably more than that.
Do all cells have the same number of mitochondria?
No. The number varies with a cell's energy demands. Heart and muscle cells, which work constantly, can hold thousands, while less active cells hold far fewer. Mature red blood cells have none at all.
Why do mitochondria have their own DNA?
Mitochondria are thought to descend from ancient bacteria absorbed into early cells over a billion years ago. They kept a small loop of their own DNA, separate from the DNA in the cell's nucleus, a leftover of that origin.
What is mitophagy?
Mitophagy is the cell's routine for identifying its most worn-out mitochondria, breaking them down, and recycling the parts, making room for fresh ones. It is a key form of mitochondrial quality control and the process urolithin A has been studied to support.
How does urolithin A relate to mitochondria?
Urolithin A has been studied for its role in supporting mitophagy, the recycling of worn-out mitochondria. The human evidence is still emerging, and any benefit is described as structure and function support, not a treatment for any condition.
Can I support my mitochondria with lifestyle?
Yes, indirectly. Regular exercise encourages your body to build more mitochondria, and sleep and a balanced diet supply the raw materials they need. Supplements are meant to complement, not replace, these basics.
Explore SOMA HEALTH Urolithin A Gummies
Keep exploring with our complete urolithin A guide, our roundup of the best urolithin A gummies, and our overview of mitochondrial health.
*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.
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