Illustration of a mitochondrion inside a cell
Mitochondria convert the food you eat and the oxygen you breathe into the energy your cells run on.

Almost every cell in your body carries tiny structures called mitochondria, and their main job is to convert the food you eat and the oxygen you breathe into a chemical fuel your cells can actually use. When people talk about feeling energetic or foggy, driven or drained, part of what they're describing traces back to how well this cellular machinery is working. It's a genuinely important system — though, as with most things in biology, the story is richer and more uncertain than the headlines suggest.

What mitochondria actually do

You've probably heard mitochondria called "the powerhouse of the cell." That nickname is fair: they produce most of the body's adenosine triphosphate, or ATP, the molecule cells spend to power everything from muscle contraction to nerve signalling to the constant background work of staying alive. Tissues that burn a lot of energy — your heart, brain, and working muscles — are especially dense with them.

But energy production is only part of the picture. Mitochondria also help regulate cell death, buffer calcium, contribute to immune signalling, and act as sensors of your metabolic state. Thinking of them purely as batteries undersells how deeply they're woven into how a cell behaves.

Why they matter for energy, ageing and the brain

When mitochondria don't function well, cells have less usable energy and generate more of the reactive byproducts that come with burning fuel. Researchers have linked this kind of mitochondrial dysfunction to a wide range of conditions — including insulin resistance, cardiovascular disease, and several neurodegenerative diseases — and it's one of the recognised biological features that tends to accompany ageing.

It's worth being careful here. An association is not the same as a proven cause, and "linked to ageing" does not mean mitochondria are the single cause of ageing or that fixing them reverses it. What the evidence supports is more modest and still useful: mitochondrial health is one meaningful thread in the larger fabric of metabolic and brain health, not a master switch you can simply flip.

What genuinely helps

The most robust lever is physical activity. Endurance and aerobic exercise are among the best-studied ways to increase both the number and the quality of mitochondria in muscle, a process called mitochondrial biogenesis. So-called "zone 2" training — a moderate intensity where you can still hold a conversation — is popular for this because it can be sustained long enough to provide a real stimulus, though higher-intensity intervals help too. The useful takeaway is simply that consistent aerobic movement is a well-supported way to keep this system healthy, not that one specific zone is magic.

Beyond exercise, the fundamentals matter more than any supplement. Regular sleep supports the metabolic housekeeping that keeps cells efficient. A diet built around whole foods, adequate protein and unsaturated fats gives mitochondria good raw materials, while chronic overeating and very high blood sugar place them under sustained strain. Not smoking and keeping alcohol moderate matter too, since both add to oxidative and metabolic stress.

The supplement question

Compounds such as CoQ10, creatine, and various B vitamins are often marketed for "mitochondrial support," and a few have reasonable evidence in specific situations — for example, CoQ10 in certain diagnosed deficiencies, or creatine for exercise performance. For a generally healthy person eating a varied diet, though, the evidence that these meaningfully boost energy or slow ageing is weak and often preliminary.

Treat supplements as a possible minor addition once the basics are in place, not a substitute for them. If you have symptoms like persistent, unexplained fatigue or muscle weakness, that's a reason to see a clinician rather than to self-prescribe — those symptoms have many possible causes.

The single most reliable thing you can do for your mitochondria isn't a pill — it's moving your body regularly, sleeping enough, and eating in a way your metabolism can keep up with.

Key takeaways

  • Mitochondria convert food and oxygen into ATP, the fuel your cells run on, and are densest in high-energy tissues like heart, brain and muscle.
  • Mitochondrial dysfunction is associated with insulin resistance, cardiovascular disease and neurodegeneration, and tends to accompany ageing — but association is not proven cause.
  • Aerobic exercise is the best-supported way to build mitochondrial capacity; sleep, whole-food nutrition and limiting alcohol and smoking round it out.
  • Most "mitochondrial" supplements have weak evidence in healthy, well-nourished people; unexplained fatigue deserves a clinician, not self-prescribing.

The bottom line

Mitochondrial health is a real and important part of how you feel and how you age, but it isn't a hidden dial you can turn to unlock energy or longevity on demand. The interventions that genuinely help are the unglamorous ones — regular movement, decent sleep, sensible eating — and they help your whole body, not just your cells' power plants. Frame the mechanism as useful context, not a promise.

What Pheno can add

Pheno doesn't measure mitochondrial function directly — no consumer test does that cleanly. What it can do is read three layers together to give you context around the metabolic and lifestyle factors that affect this system. On the physical side, blood biomarkers such as fasting glucose, HbA1c, a lipid panel and markers of inflammation reflect the metabolic strain that mitochondrial health sits inside. Through wearable integration, Pheno pulls in your steps, resting heart rate and sleep — the exact behaviours that most reliably support mitochondrial capacity. And validated wellbeing surveys capture the fatigue and stress side that raw numbers miss. The honest limit: these are indirect signals, and a single test is a snapshot — the value comes from repeating tests over time so you can see a trend rather than a one-off verdict.

Frequently asked questions

Can a blood test measure my mitochondrial health?

Not directly, in routine care. Specialised tests exist in research and for diagnosing specific mitochondrial diseases, but there's no simple consumer blood test that scores everyday mitochondrial function. Standard markers instead tell you about the surrounding metabolic picture.

Is zone 2 training really the best exercise for mitochondria?

It's a well-supported option, not a uniquely magic one. Sustained moderate aerobic exercise reliably stimulates mitochondrial adaptations, and higher-intensity intervals help as well. Consistency matters more than hitting one precise heart-rate zone.

Do mitochondrial supplements work?

For most healthy people eating a varied diet, the evidence for energy or longevity benefits is weak or preliminary. A few compounds help in specific, diagnosed situations. It's reasonable to prioritise sleep, food and movement first.

Can I reverse ageing by improving my mitochondria?

No. Mitochondrial changes accompany ageing, but improving mitochondrial health won't reverse it. What you can realistically do is support your metabolic and brain health, which is worthwhile on its own terms.

Can Pheno tell me if my mitochondria are the reason I feel tired?

Not on its own, and it won't diagnose a mitochondrial disorder. What Pheno can do is combine your metabolic blood markers, wearable sleep and activity data, and wellbeing surveys to surface patterns worth discussing, and flag when persistent fatigue is a reason to see a clinician.

This article is general education, not medical advice. Persistent or unexplained fatigue, muscle weakness or exercise intolerance can have many causes, some serious, and should be assessed by a qualified clinician rather than self-treated. Always consult a healthcare professional before starting supplements or making significant changes to exercise or diet, especially if you have an existing condition.

Sources & methodology

This article draws on widely cited reviews of mitochondrial biology, exercise physiology and the biology of ageing; claims are framed to reflect current mainstream consensus and its uncertainties.

  • López-Otín C, et al. Hallmarks of aging: an expanding universe. Cell. 2023;186:243-278.
  • Hood DA, et al. Maintenance of skeletal muscle mitochondria in health, exercise, and aging. Annu Rev Physiol. 2019;81:19-41.
  • Nunnari J, Suomalainen A. Mitochondria: in sickness and in health. Cell. 2012;148:1145-1159.
  • Memme JM, et al. Exercise and mitochondrial health. J Physiol. 2021;599:803-817.