Understanding Mitochondria: Your Body's Energy Powerhouse

What Are Mitochondria?

Mitochondria are tiny structures found inside almost every cell in your body. You may remember them from school as the "powerhouses of the cell" — and the nickname fits. Their main job is to turn the food you eat into energy your body can actually use.[1,2]

Some cells contain just a handful of mitochondria; others hold thousands. The busiest, most energy-hungry parts of the body — your heart, muscles and brain — are packed with them.[1] But making energy is only part of the story. Mitochondria turn out to be involved in a surprising range of jobs, which is why scientists increasingly see them as central to overall cellular health.[1,2]

How Mitochondria Make Energy

Your body runs on a molecule called ATP. Think of it as cellular fuel: almost everything your body does — moving a muscle, firing a nerve, repairing tissue — is powered by it.[2,3]

Mitochondria are where most of that fuel gets made. Inside them, the nutrients from your food (carbohydrates, fats and proteins) are gradually broken down and converted into ATP, in a process that uses oxygen.[3,4] This is a big part of why we breathe: oxygen is essential to the final step of energy production.[3,4]

The system is remarkably efficient, producing far more usable energy from your food than the body's quicker, oxygen-free backup pathways can.[5] When people talk about "cellular energy," this is largely what they mean — and mitochondria are at the heart of it.[2,3]

More Than Just Energy

Energy is the headline, but mitochondria quietly do a lot more behind the scenes:[1,2]

• Cell signalling — they help cells communicate and respond to their environment.[6]
• Calcium balance — they help manage calcium, which matters for things like muscle and nerve function.[1]
• Metabolism — they help build some of the body's essential molecules, not just break things down.[6]
• Cell renewal — they help the body clear out old or damaged cells in a controlled, healthy way.[1,2]
• Heat — in some tissues, they help keep you warm.[6]

A Cell Within a Cell

Here's a genuinely strange fact: mitochondria carry their own small set of DNA, separate from the DNA in the rest of the cell.[1,7] This is a clue to their unusual origin — the widely accepted theory is that mitochondria descend from ancient bacteria that were absorbed into early cells billions of years ago.[1]

That DNA is passed down almost entirely from your mother. It also sits in a busy, chemically active part of the cell with fewer repair tools than the body's main DNA, which may make it more prone to wear over time — something researchers find relevant when they study ageing.[7]

Mitochondria and Ageing

One consistent theme in ageing research is that mitochondria tend to work a little less efficiently as we get older. This gradual change is considered one of the recognised "hallmarks of ageing."[8,9]

Over time, the body can become slower at making new mitochondria and at clearing away worn-out ones.[9,10] Research has linked these shifts to lower energy production and to age-related changes in tissues like muscle, including the gradual loss of strength known as sarcopenia.[9,10] These relationships are complex and still being worked out, and mitochondrial change is just one piece of a much bigger ageing picture — not the whole story.[8,9]

The NAD+ Connection

Mitochondria rely on a helper molecule called NAD+ to make energy, and NAD+ also supports a family of enzymes (called sirtuins) that help keep mitochondria in good working order.[3,6,11] Because NAD+ naturally declines with age, it's one of the threads researchers are following as they explore the link between cellular energy and ageing — though, as with much of this field, the human evidence is still developing.[8,11]

What Can Influence Mitochondrial Health?

Physical Activity

Exercise is the single most well-established way to support your mitochondria. When you're active, your cells respond to the extra energy demand by building more mitochondria.[10,12] Both cardio and strength training have been associated with improvements, though the details vary from person to person.[10,12]

Nutrition

Mitochondria need a steady supply of good nutrients to do their work, and overall diet quality is closely tied to metabolic health.[9]

Sleep and Recovery

Quality sleep gives your body time to carry out the cellular maintenance that keeps tissues — and the mitochondria inside them — running well.[9]

Everyday Balance

Things like managing stress and going easy on alcohol and smoking all play into the bigger picture of cellular health.[6,9]

Common Myths About Mitochondria

Myth 1: Mitochondria Only Make Energy

As we've seen, they're also involved in signalling, metabolism, calcium balance and cell renewal — energy is just their best-known role.[1,2]

Myth 2: There's One Simple Fix for Mitochondrial Health

Mitochondrial health is shaped by many factors working together rather than any single one. Lifestyle foundations — regular movement, good sleep and quality nutrition — are the most consistently supported, and some people choose to complement these with targeted nutritional support. What's worth being cautious about is any claim of instant or dramatic results from one quick fix.[8,10,12]

Myth 3: Mitochondrial Decline With Age Is Set in Stone

Some change is a natural part of getting older, but research suggests lifestyle — especially staying active — can meaningfully influence mitochondrial capacity well into later life.[10,12]

Supporting Healthy Mitochondrial Function

Mitochondrial biology is intricate, but the habits that support it are refreshingly familiar — they're the same foundations that support good health overall:[9,10,12]

• Move regularly, mixing cardio and strength work
• Eat a balanced, nutrient-rich diet
• Prioritise quality sleep and recovery
• Manage stress and look after your metabolic health
• Go easy on alcohol, and avoid smoking
• Check in with a healthcare professional about your individual needs

Mitochondria sit right at the centre of how your body makes energy and stays healthy — which is exactly why they're one of the most studied topics in biology today. And the encouraging part is that supporting them isn't about chasing any single magic fix. It comes down to the steady, sustainable habits that are good for you all round.[9,12]

References

1. Nunnari J, Suomalainen A. Mitochondria: in sickness and in health. Cell. 2012;148(6):1145-1159.
2. Spinelli JB, Haigis MC. The multifaceted contributions of mitochondria to cellular metabolism. Nature Cell Biology. 2018;20(7):745-754.
3. Martínez-Reyes I, Chandel NS. Mitochondrial TCA cycle metabolites control physiology and disease. Nature Communications. 2020;11:102.
4. Vercellino I, Sazanov LA. The assembly, regulation and function of the mitochondrial respiratory chain. Nature Reviews Molecular Cell Biology. 2022;23(2):141-161.
5. Nath S, Villadsen J. Oxidative phosphorylation revisited. Biotechnology and Bioengineering. 2015;112(3):429-437.
6. Chandel NS. Mitochondria as signaling organelles. BMC Biology. 2014;12:34.
7. Stewart JB, Chinnery PF. The dynamics of mitochondrial DNA heteroplasmy: implications for human health and disease. Nature Reviews Genetics. 2015;16(9):530-542.
8. López-Otín C, Blasco MA, Partridge L, Serrano M, Kroemer G. Hallmarks of aging: An expanding universe. Cell. 2023;186(2):243-278.
9. Yang J, et al. Mitochondrial dysfunction in aging. Ageing Research Reviews. 2023;88:101955. Available at: https://www.sciencedirect.com/science/article/abs/pii/S1568163723001149
10. Mitochondrial Adaptations in Aging Skeletal Muscle: Implications for Resistance Exercise Training to Treat Sarcopenia. Life (Basel). 2024;14(8):962. Available at: https://www.mdpi.com/2075-1729/14/8/962
11. Mitochondrial sirtuins, key regulators of aging. 2025. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12342567/
12. Bishop DJ, Botella J, Genders AJ, et al. High-Intensity Exercise and Mitochondrial Biogenesis: Current Controversies and Future Research Directions. Physiology. 2019;34(1):56-70.

This article is intended for general educational purposes only and does not constitute medical advice. Individual health needs vary; please consult a qualified healthcare professional regarding any personal health concerns.