The modern Western diet provides an extraordinary abundance of calories but is chronically deficient in many of the micronutrients that cellular energy production depends on. This creates a paradox of energy affluence and energy deficit simultaneously: plenty of substrate but impaired machinery to convert it. Understanding which micronutrients are most critical to cellular energy, where they are found in food, and who is most at risk of deficiency provides a practical framework for addressing the epidemic of fatigue that characterises contemporary life.
B Vitamins: The Energy Metabolism Vitamins
The B vitamin family is the most directly involved in energy metabolism. Thiamine is the cofactor for pyruvate dehydrogenase, the enzyme that converts pyruvate into acetyl-CoA for entry into the Krebs cycle. Riboflavin is the precursor of FAD, the electron carrier at Complexes I and II. Niacin is the precursor of NAD+, the most important electron carrier in the entire pathway; NAD+ decline with age is increasingly recognised as a central driver of metabolic ageing. Pantothenic acid forms the core of coenzyme A. Vitamin B6 is required for glycogenolysis and gluconeogenesis. B12 and folate are required for one-carbon metabolism, which underpins the methylation reactions involved in mitochondrial protein synthesis.
Magnesium: The Gatekeeper of Energy Reactions
Magnesium is required for over 300 enzymatic reactions, a significant proportion of which are involved in energy metabolism. ATP is biologically inactive unless chelated with magnesium, meaning that all ATP-requiring reactions depend on magnesium. Magnesium is also required for the function of pyruvate kinase, the key glycolytic enzyme, and for the activation of the adenylate cyclase involved in the cyclic AMP signalling that modulates metabolic rate. UK dietary surveys consistently find that a significant proportion of adults consume below the reference nutrient intake for magnesium. The richest dietary sources are pumpkin seeds, almonds, dark chocolate, spinach, and avocado.
Iron: The Oxygen Carrier and Energy Enzyme Core
Iron is required for haemoglobin, which carries oxygen to tissues, and for the cytochrome enzymes of Complexes III and IV in the electron transport chain. Iron deficiency anaemia is well recognised as a cause of fatigue. What is less widely appreciated is that iron deficiency without anaemia, in which ferritin is low but haemoglobin remains normal, also causes fatigue through impairment of the iron-dependent mitochondrial enzymes. Studies have found that ferritin below 30 micrograms per litre is associated with fatigue and reduced exercise performance, even in the absence of anaemia. Iron-rich foods include red meat, liver, lentils, dark chocolate, and tofu; the iron in plant foods is non-haem iron and is better absorbed when consumed with vitamin C.
Other Critical Energy Micronutrients
- Coenzyme Q10: the mobile electron carrier between the protein complexes of the electron transport chain; not strictly a vitamin since the body synthesises it, but synthesis declines with age and is reduced by statin use; 100 to 200 mg ubiquinol daily is appropriate in those over 50 or taking statins
- Vitamin D: receptors for vitamin D are found in mitochondria; deficiency reduces mitochondrial function and is associated with unexplained fatigue; over 1 billion people globally are estimated to be deficient
- Zinc: required for over 300 enzymes including lactate dehydrogenase in glycolysis and the superoxide dismutase that protects mitochondria from oxidative damage
- Iodine: required for thyroid hormone synthesis; thyroid hormones regulate basal metabolic rate; subclinical hypothyroidism, increasingly common in the UK, causes profound fatigue through reduced mitochondrial density and function
- Vitamin C: required for carnitine synthesis; carnitine transports long-chain fatty acids into the mitochondria for beta-oxidation; vitamin C deficiency impairs fat burning even before overt scurvy symptoms appear
Sources
- Tardy, A.L., et al. (2020). Vitamins and minerals for energy, fatigue and cognition. Nutrients, 12(1), 228.
- Moretti, R., & Peinkhofer, C. (2019). B vitamins and fatty acids: what do they share with small vessel disease-related dementia? International Journal of Molecular Sciences, 20(22), 5797.
- Camaschella, C. (2015). Iron-deficiency anemia. New England Journal of Medicine, 372(19), 1832-1843.
- Nielsen, F.H., & Lukaski, H.C. (2006). Update on the relationship between magnesium and exercise. Magnesium Research, 19(3), 180-189.
- Landi, F., et al. (2016). Animal sources and essential amino acids in older adults. Ageing Research Reviews, 27, 96-103.