Oxygen transport
Iron is a core component of hemoglobin in red blood cells and myoglobin in muscle tissue, enabling oxygen delivery from lungs to tissues and carbon dioxide removal.
Energy metabolism
Required for mitochondrial cytochromes involved in ATP production. Iron deficiency impairs oxidative phosphorylation even before anemia develops, causing fatigue and reduced work capacity.
Cognitive function
Iron is essential for dopamine and serotonin synthesis, myelin formation, and neuronal energy metabolism. Deficiency in children impairs cognitive development, attention, and learning.
Immune support
Required for proliferation of immune cells and production of reactive oxygen species by macrophages to kill pathogens. Both deficiency and excess impair immune function.
Hemoglobin and myoglobin formation
Iron binds to protoporphyrin IX to form heme, which is incorporated into globin proteins to create hemoglobin and myoglobin. Each hemoglobin molecule contains four iron atoms.
Electron transport chain function
Iron-sulfur clusters and heme groups in Complexes I, II, III, and IV of the mitochondrial electron transport chain shuttle electrons during oxidative phosphorylation, producing the majority of cellular ATP.
Neurotransmitter synthesis
Iron is a cofactor for tyrosine hydroxylase (dopamine synthesis) and tryptophan hydroxylase (serotonin synthesis). Deficiency reduces neurotransmitter production, affecting mood, attention, and cognitive performance.
RCT of 80 mg/day iron vs. placebo in 198 women with fatigue and low ferritin but no anemia over 12 weeks.
198 women aged 18–53. 12-week intervention.
Iron supplementation significantly reduced fatigue scores compared to placebo. Improvement correlated with ferritin level increases. Demonstrates benefit in functional iron deficiency before anemia develops.
Systematic review of 14 RCTs examining iron supplementation effects on cognitive function in iron-deficient adolescent girls.
Multiple RCTs in adolescent girls.
Iron supplementation improved attention, concentration, and IQ scores in iron-deficient adolescents. Effects most pronounced in those with lowest baseline ferritin levels.