03 Energy Metabolism: What Your Mitochondria Really Need

Your energy is made in your mitochondria, the tiny power plants inside almost every cell. To turn food and oxygen into energy, they need building blocks such as iron, vitamin B12 and magnesium. Your blood tests don't measure your mitochondria directly – but they do show whether these building blocks are available. And that is where you can act most reliably.

Few health topics are as hyped right now as "mitochondrial health". NAD+ boosters, cell-renewal protocols, energy complexes: there is a lot of money in the promise of rejuvenating your own power plants. That makes an honest look all the more important – at what biology can clearly tell us today, and what it can't (yet).

What actually happens in energy metabolism?

Your body turns food into ATP, the energy currency of your cells. Think of a power plant: carbohydrates and fats are the fuel, and ATP is the electricity that runs your heart, brain and muscles. Most of that electricity is generated in the mitochondria.

This doesn't happen in one step. It works more like an assembly line with several stations. Enzymes do the work at each station, and many of them only function with the right tools:

Station	What happens	What it needs
1. Deliver fuel	Sugar and fat move from the blood into the cells	well-regulated blood sugar and insulin
2. Break down	The fuel is broken down step by step inside the mitochondria (in the so-called citric acid cycle)	B vitamins such as B1, B2 and B12 1
3. Respiratory chain	Electrons pass along a chain of proteins, and with oxygen, ATP is produced	iron 2 and coenzyme Q10 3
4. Use the energy	ATP powers countless processes in your cells	magnesium, which is involved in more than 600 reactions 4

Vitamin B12, for example, helps an enzyme feed a building block into the citric acid cycle ¹. Magnesium is involved in key steps of energy metabolism ⁴. If one of these tools runs short, the assembly line doesn't stop immediately – but it can slow down.

And that's the genuinely good news: energy metabolism has clear points where you can make a difference. Some show up in your blood, others can be trained through movement.

Why does iron deficiency cause fatigue, even without anaemia?

Because iron isn't only needed for haemoglobin, the pigment in red blood cells. It is also needed for energy production in the mitochondria ². Your iron stores can run low long before anaemia develops.

A systematic review of randomised trials looked at exactly this situation: people with iron deficiency but no anaemia. Iron treatment reduced self-reported fatigue, while measurable physical performance did not change ². Most participants were younger, healthy women ² – for other groups the data are thinner.

One detail matters: ferritin, the iron storage marker, also rises with inflammation. A "good" ferritin level can therefore hide a deficiency. That is why iron status is read from several markers, and always in light of possible inflammation ¹. It shows how closely energy metabolism is linked to other mechanisms, such as oxygen transport and silent inflammation.

Which blood tests show whether your energy metabolism is well supplied?

No blood marker directly measures how well your mitochondria are working. But several markers show whether the building blocks they need are there – and that's the part you can influence.

Marker	What it shows
Always included – Core Health blood test
Ferritin	How well your iron stores are filled. Also rises with inflammation
Iron	How much iron is circulating in your blood right now. Varies a lot over the day
Transferrin	The transport protein for iron. Rises when your body is "looking" for iron
Transferrin saturation	How much iron is actually available to your cells
TIBC and UIBC	How much transport capacity is still free. They complete the picture of your iron status
Vitamin B12	A tool in the citric acid cycle and for making blood cells
Magnesium	Involved in many energy-dependent reactions. Blood shows only a small share of your body's stores
Fasting glucose	How well your fuel supply is regulated
For a deeper look – add-on tests
Coenzyme Q10	Electron carrier in the respiratory chain. Statins can lower its level
TSH, fT4, fT3 and T3/T4 ratio	Your thyroid helps set the pace of your metabolism. The ratio shows how well the active hormone is formed
Vitamin B1 (thiamine)	Helps feed sugar into the mitochondria as fuel
Vitamin B2 (riboflavin)	A building block of electron carriers in the respiratory chain
Vitamin B6	Important for getting energy from protein and stored sugar
Vitamin B7 (biotin)	A tool in sugar and fat metabolism
Vitamin B9 (folate)	Works together with B12 in making blood cells
Vitamin C	Improves iron absorption from plant foods
Vitamin E	Protects cell membranes from oxidative stress
Vitamin A and beta-carotene	Show your supply – including possible oversupply from supplements
Vitamin K1 and K2	Vitamin K status. K1 reflects your diet, K2 is mainly meaningful if you take it
Omega-3 index	The share of omega-3 fatty acids in your cell membranes
Selenium	Protects cells from oxidative stress and is needed for active thyroid hormone
Zinc	A tool for numerous enzymes
Copper	Part of the respiratory chain and important for iron metabolism

The markers in the Core Health blood test are included in every test. If you want a deeper look, you can add coenzyme Q10, thyroid markers, selenium, zinc and further vitamins through add-on tests.

It gets interesting when you combine them. A low-normal ferritin in someone who does a lot of endurance training tells a different story than the same value in someone with raised inflammation markers. Alcohol, sleep, physical activity and medications such as statins also feed into energy metabolism. That's why we never look at these markers in isolation.

Mitochondria boosters, NAD+, cell renewal: what's proven and what isn't?

That mitochondria are central to your energy is well established. That you can rejuvenate them with a capsule is not – at least not so far.

The promise	What studies in humans show
NAD+ boosters (e.g. NR, NMN) rejuvenate your mitochondria	They raise NAD+ in the blood but have shown few clinically relevant effects so far. Mitochondrial function in muscle did not improve in trials 5
High-dose antioxidants protect your cells	For preventing cardiovascular disease and cancer, the US Preventive Services Task Force recommends against beta-carotene and vitamin E. For multivitamins, the evidence is insufficient 6
Coenzyme Q10 gives everyone more energy	Q10 is essential in the respiratory chain. But even in a rare inherited deficiency, the benefit of taking it is only weakly supported 3
Exercise builds mitochondria	Well supported, including in older age 7

This doesn't mean this research has no place. For NR, for example, there are early signs that inflammation markers in the blood may fall – that deserves solid follow-up studies ⁵. But a review of all NR trials to date also found that results have often been presented as stronger than the data support ⁵. What looks impressive in cell culture or animal studies still has to prove itself in people.

Can exercise build more mitochondria?

Yes – and it's the best-supported route. In a randomised trial, younger and older adults trained for twelve weeks ⁷. Interval training improved mitochondrial respiration in muscle and aerobic capacity. In the older participants, it reversed many age-related differences in mitochondrial proteins ⁷.

What about strength training? It improved insulin sensitivity and muscle mass, but not mitochondrial respiration. Combining moderate endurance and strength training achieved both ⁷. The study was small, but the message is clear: endurance and intervals train your power plants, strength trains your muscles and blood sugar. The mix brings the most.

The encouraging part: it's never too late. Older muscles in particular responded clearly to training ⁷.

What role does coenzyme Q10 play?

Coenzyme Q10 is one of the most important helpers in your power plants. In the respiratory chain, it picks up electrons and carries them on, like a relay runner taking the baton from one station to the next. Only at the end of this chain is ATP produced ³. Q10 collects electrons from several sources, including the breakdown of fats ³. Without Q10, the respiratory chain can’t work properly. Your body makes it itself, through the same metabolic pathway it uses to make cholesterol.

That’s why a deficiency is never good. When Q10 is missing, the organs with the highest energy needs are hit first, such as the heart, muscles, kidneys and brain ³. How well a deficiency can be corrected by supplementation is still being researched. Even in rare inherited forms, the results are mixed ³. That makes it all the more valuable to know your own level instead of supplementing on a hunch.

Q10 is especially interesting for anyone taking cholesterol-lowering statins. Because statins slow down the very pathway that also produces Q10, they lower Q10 levels in the blood ⁸. One meta-analysis found that supplementation can relieve statin-related muscle symptoms ⁸, while an earlier one saw no benefit ⁹. Research here is moving. If you take a statin, you can have your Q10 level measured through an add-on test and see how it changes over time. Always discuss muscle symptoms with your doctor – and never stop the medication on your own. Why statins can matter so much for your arteries is explained in our article on atherosclerosis risk.

When does a supplement make sense?

When there is a deficiency – and when you check afterwards whether it has been corrected. In iron deficiency without anaemia, iron-rich food or a supplement can help reduce fatigue ². The European micronutrient guideline follows the same order: assess status, give what's needed, monitor ¹.

For healthy people without a deficiency, however, the benefit of taking supplements "just in case" is not established ⁶. And more isn't automatically better: too much iron can also cause harm ¹.

So our principle is simple: only supplement what you actually need. Measure first. Then see whether a deficiency can be corrected through food. Supplement in a targeted way where necessary. And at your next test, check whether your stores are actually filling up.

What can you do?

The first step is knowing your building blocks. The decisive step is staying with it and seeing what works. Here's how that can look with speak23:

1. Know your building blocks. The Core Health blood test shows your iron status, vitamin B12, magnesium and fasting glucose in context. To go deeper, add the Comprehensive Vitamins & Trace Elements test.
2. See the trend, not a snapshot. With 2 or 4 tests a year, all your values are recorded digitally and automatically. A slowly falling ferritin, for example, becomes visible early.
3. Plate first, then pill. You receive three evidence-based recommendations tailored to your blood results and your personal health history, such as your activity, sleep or medications. A supplement only comes in when your values point to it.
4. See whether your stores are filling up. At your next test, the app shows whether your changes are reflected in your values – and whether you still need a supplement.
5. Use movement as mitochondria training. If it fits your profile, movement becomes a core part of your recommendations. You can follow its effect on blood sugar and other markers over time.
6. Get persistent fatigue checked by a doctor. Fatigue has many causes, from sleep to thyroid to mood, that no single blood marker captures. You get specific questions to take to your doctor. speak23 does not replace a diagnosis. For the bigger picture, read our overview Understanding blood tests: why connections matter. How fuel supply can get out of balance is explained in our article on insulin resistance.

Where is medicine heading on energy and mitochondria?

Today's evidence is honest and still encouraging. The building blocks of energy metabolism can be measured, deficiencies are treatable ¹², and exercise demonstrably builds up your power plants, at any age ⁷. Miracle products that rejuvenate mitochondria, on the other hand, are not supported so far ⁵.

Fatigue is often accepted as just part of getting older. We believe that can change. When people know their building blocks regularly, act on evidence rather than guesswork, and see what their choices achieve, they regain a piece of self-determination over their health. Not data for the sake of data, but more energy for what matters – and, we hope, more healthy years.

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