Energy is a cellular function

You’re not imagining it. Even after resting, your energy still doesn’t return. This kind of tiredness doesn’t feel like a bad night’s sleep. It’s persistent. Heavy.
As if your body is trying but running on low power. If that sounds familiar, there’s a reason for it, and it starts at the cellular level.

The hidden engine behind your energy

Inside every cell in your body, there are microscopic structures called mitochondria.
They’re often described as the cell’s “powerhouses,” and for good reason: they produce ATP (adenosine triphosphate), the molecule that fuels nearly every biological function, from brain activity and digestion to movement and mood.

ATP is your body’s true energy source. You don’t “feel” tired because you need more sleep; you feel tired when your cells aren’t producing enough ATP to meet demand. That’s why rest doesn’t always work. If your mitochondria can’t keep up, your body can’t recharge, no matter how many hours you spend in bed.

What your body needs to make energy

Mitochondria can’t produce ATP out of thin air. They rely on specific nutrients to convert the food you eat into usable energy.

Here’s what that system depends on:

1. B-vitamins

These are the unsung heroes of cellular metabolism.

•    Vitamin B1 (thiamine) helps convert carbohydrates into energy.
•    B2 (riboflavin) and B3 (niacin) are essential for the electron transport chain, the final step in ATP production.
•    B6, folate, and B12 help regulate red blood cell formation and methylation processes that impact oxygen delivery and energy balance.
Even small deficiencies can impair mitochondrial function. And these are among the most common vitamin gaps in adults, especially B12 in vegans and older adults.

2. Magnesium

Every molecule of ATP in your body must bind to magnesium to be biologically active.
If magnesium is low, ATP can’t do its job, even if it’s being produced.

3. Iron

Iron is crucial for transporting oxygen to your cells, and without oxygen, mitochondria can’t complete the energy production process.
Low iron = low oxygen delivery = low ATP.

4. Oxygen

Yes, even your breath matters. Mitochondria use oxygen in a process called oxidative phosphorylation to generate the bulk of your ATP. If oxygen flow is impaired by low iron, poor circulation, or stress, you’ll feel it as fatigue.

How to support energy at the source

The problem with most energy solutions is that they treat symptoms.
Coffee, sugar, and even some supplements are designed to stimulate, not support.

Real energy comes from helping your cells function better, by giving your mitochondria what they need to make ATP efficiently.

That’s why a high-quality multivitamin shouldn’t just be a checklist.
It should include:

•    Activated B-vitamins (like methylfolate and methylcobalamin) so your body can absorb and use them easily
•    Magnesium in a bioavailable form like magnesium citrate or glycinate
•    Iron in low but effective doses to support oxygen delivery without constipation
•    Antioxidants like vitamin C, E, and selenium to protect mitochondria from oxidative damage
•    And ideally, ingredients like CoQ10 or alpha-lipoic acid, which directly support mitochondrial health (especially in adults over 30)

Whether it’s through your diet, your supplements, or both, supporting cellular energy is one of the most powerful things you can do for how you feel, think, and function. Because real energy isn’t something you push through.
It’s something your body builds if you give it the chance.

References

1.    Kennedy, D. O. (2016). B Vitamins and the Brain: Mechanisms, Dose and Efficacy—A Review. Nutrients, 8(2), 68.
→ Reviews how B-complex vitamins support cognitive and energy function through their role in cellular metabolism.
https://doi.org/10.3390/nu8020068
2.    Ragsdale, S. W., & Kumar, M. (1996). Nickel-dependent enzymes. Annual Review of Biochemistry, 65(1), 1–28.
→ Describes ATP-dependent enzymes and the essential cofactors required for mitochondrial function.
3.    Wallace, D. C. (2005). A mitochondrial paradigm of metabolic and degenerative diseases, aging, and cancer: a dawn for evolutionary medicine. Annual Review of Genetics, 39, 359–407.
→ Explains the central role of mitochondria and mitochondrial DNA in energy production and disease.
4.    Barbagallo, M., & Dominguez, L. J. (2010). Magnesium and aging. Current Pharmaceutical Design, 16(7), 832–839.
→ Shows how magnesium deficiency affects ATP activation and energy metabolism, particularly with age.
5.    Hentze, M. W., Muckenthaler, M. U., & Andrews, N. C. (2004). Balancing acts: molecular control of mammalian iron metabolism. Cell, 117(3), 285–297.
→ Covers how iron is regulated in the body and its essential role in oxygen transport and energy.
6.    Rich, P. R. (2003). The molecular machinery of Keilin’s respiratory chain. Biochemical Society Transactions, 31(6), 1095–1105.
→ Details oxidative phosphorylation and the role of oxygen in mitochondrial ATP production.