Cellular energy & healthy ageing

This is the cluster about why energy feels different as the years pass — and it sits under our main guide, why am I always tired? If your tiredness is new, heavy, or recent, start there first, because the most common drivers (iron, B12, vitamin D, sleep, stress) are often quicker to address than ageing itself. This page is for the slower, longer question: what is actually happening inside your cells over a lifetime, and where do nutrition and lifestyle genuinely fit?

What are mitochondria, and why do they matter for energy?

Mitochondria are microscopic structures inside almost every cell — often called the cell's power plants. They take the food you eat and the oxygen you breathe and convert them, step by step, into a molecule called ATP (adenosine triphosphate), the universal fuel your cells spend on everything from thinking to moving a muscle. A single hard-working cell, like a heart-muscle cell, can hold thousands of mitochondria. When they work well, you have spare capacity; when they don't, the same effort feels heavier.

The reason mitochondria matter for ageing is that they are both the engine and, over time, one of the first things to wear. A 2025 review in Nature's Signal Transduction and Targeted Therapy describes how mitochondria are central not only to energy but to the wear-and-tear processes of getting older. That is why so much of the healthy-ageing conversation eventually circles back to these tiny power plants.

Why does energy decline with age at the cellular level?

Energy declines with age partly because mitochondria become fewer and less efficient. Human muscle studies report ATP-producing capacity falling around 8% per decade, alongside reduced oxidative capacity. The cell still works — but with less spare headroom, so recovery is slower and the same day can quietly demand more.

Three things tend to happen together as cells age. First, the machinery that builds new mitochondria slows, so there are fewer of them. Second, the ones that remain leak more and convert fuel less efficiently — a 2006 review in the American Journal of Physiology describes decreased electron-transfer rates and a 'leakier' inner membrane that wastes some of the energy gradient. Third, the cell's housekeeping system that recycles worn-out mitochondria (a process called mitophagy) becomes less active, so damaged units accumulate. Importantly, this is a gradual drift over decades — not a sudden switch — and lifestyle has real influence on the pace.

Aged tissues show a decreased capacity to produce ATP by oxidative phosphorylation due to dysfunctional mitochondria — including decreased electron-transfer rates and impaired ATP synthesis. American Journal of Physiology – Cell Physiology, 2006

If you want the everyday version of this — the lived experience of feeling that energy just isn't what it was — we cover it plainly in is it normal to feel more tired as you get older?

What is CoQ10 and what does it do in the energy chain?

CoQ10 (coenzyme Q10, also called ubiquinone) is a fat-soluble molecule your body makes itself. Inside the mitochondria, it works as a shuttle — carrying electrons between the protein complexes that together produce ATP. The body's own production is highest at around age 20 and gradually declines after, with the heart and kidneys among the tissues showing the clearest age-related drop.

A 2019 open-access review, The Paradox of Coenzyme Q10 in Aging, explains CoQ10's dual job: it is 'an essential electron carrier in the mitochondrial respiratory chain' and, at the same time, a membrane antioxidant that helps protect cell membranes from oxidative wear. That double role is exactly why it comes up so often in conversations about cellular energy and ageing. We unpack the evidence — what is established, what is still uncertain — in the dedicated explainer, CoQ10, explained without the hype.

What is oxidative stress, and how does it relate to ageing?

Oxidative stress is the imbalance between reactive molecules called free radicals — a normal by-product of making energy — and the antioxidant defences that neutralise them. When production outpaces defence, free radicals can damage cell parts, including the DNA inside mitochondria. That mitochondrial DNA is especially exposed: one review found an oxidative-damage marker 16 times higher there than in the cell's main DNA.

The idea that this accumulating damage drives ageing is the 'free radical theory of ageing', first proposed by Denham Harman in the 1950s and updated by him in 2006. It is genuinely influential — but the science has matured into a more nuanced view. Some free-radical signalling is useful, and simply flooding the body with antioxidant supplements has not reliably extended lifespan in studies, as Scientific American has reported. So the honest position is: oxidative stress is real and matters, but more antioxidants is not automatically better. We give this its own careful treatment in oxidative stress, explained, and look at where antioxidants actually help versus where it's hype in antioxidants, energy and ageing.

Which nutrients play a role in cellular energy?

Several nutrients have officially recognised roles in energy metabolism — meaning the cell physically cannot run its ATP-making chemistry without them. These are supporting roles in normal function, not treatments for any condition. European food-safety assessors (EFSA) have substantiated specific structure-function claims for several of them.

For example, niacin (vitamin B3) and vitamin C are recognised as contributing to normal energy-yielding metabolism and to the reduction of tiredness and fatigue. Magnesium is needed for normal energy-yielding metabolism, and iron contributes to normal oxygen transport — the oxygen that mitochondria need to make ATP. A 2018 systematic review found iron supplementation reduced self-reported fatigue in non-anaemic but iron-deficient adults. None of this means a supplement 'boosts' energy in someone already well-nourished; it means a genuine shortfall in one of these nutrients can show up as tiredness. We cover who actually needs what in foundational nutrient status.

What can I actually do to support cellular energy as I age?

The most reliable lever for cellular energy is not a pill — it is movement. Exercise prompts the body to build more and healthier mitochondria, a process called mitochondrial biogenesis, and studies show it can partly rescue mitochondrial efficiency in ageing muscle. Sleep, a varied whole-food diet, and not smoking round out the foundation.

Beyond that, the honest answer is genuinely individual. Whether a specific nutrient matters for you depends on your diet, your blood results, your age and your stage of life — which is exactly why a five-minute conversation with someone who reads the studies can beat hours of searching. If your fatigue is new, severe, or not improving, please see a healthcare professional, because some causes need proper medical attention rather than nutrition tweaks.

Frequently asked questions