Persistent fatigue is one of the most common complaints among adults over 35. It is frequently attributed to age, stress, or poor sleep when the dietary contribution is substantial and often primary. Systemic inflammation from a poor-quality diet produces fatigue through cytokine action on brain chemistry, specifically through the sickness behaviour response that is mediated by inflammatory cytokines including interleukin-1 and TNF-alpha. This is the same mechanism that makes you feel exhausted when you have an infection, activated at a lower level by chronic dietary inflammation.
Nutritional Deficiencies That Drive Fatigue
- Iron deficiency: impairs oxygen delivery to tissues and mitochondrial energy production; check ferritin not just haemoglobin, as tissue iron depletion precedes anaemia; eat red meat, lentils, and dark leafy greens with vitamin C
- Vitamin B12: required for neurological function and energy metabolism; deficiency produces profound fatigue; found exclusively in animal foods; supplement if vegan or vegetarian
- Magnesium: required for ATP production in mitochondria; deficiency impairs cellular energy generation; eat dark leafy greens, pumpkin seeds, and nuts
- Vitamin D: deficiency is associated with fatigue in multiple studies; supplement 1,000 to 2,000 IU daily from October to March in northern latitudes
Blood Sugar Instability and Energy Crashes
Recurring afternoon fatigue, difficulty concentrating after lunch, and mid-morning energy crashes are classic presentations of glycaemic instability. The blood glucose spike from a refined carbohydrate-dominant meal is followed two to three hours later by reactive hypoglycaemia as insulin overshoots the glucose response. This produces cognitive impairment, fatigue, and carbohydrate cravings. Replacing refined carbohydrate meals with whole food meals containing protein, fat, and fibre eliminates this cycle for most adults.