Zinc is essential for hair follicle function, with documented roles in keratin metabolism, follicle stem cell regulation, and immune function relevant to scalp health. Frank zinc deficiency causes hair loss alongside characteristic skin findings (acrodermatitis enteropathica in severe cases). The relevance to hair loss treatment depends substantially on whether actual deficiency is present, and in Western populations with adequate dietary intake, true deficiency is uncommon.

Studies of serum zinc levels in unselected hair loss patients have produced mixed results. Some studies show modestly lower zinc levels in androgenetic alopecia and telogen effluvium patients compared to controls; others show no difference. Methodological challenges include the unreliable nature of serum zinc as a deficiency marker (it doesn't reflect tissue stores well) and the dietary variability across study populations. Hair tissue zinc has been studied but isn't well-standardised for clinical use.

Practical approach: zinc supplementation without documented deficiency provides minimal benefit and over-supplementation can cause its own problems (copper deficiency from chronic high zinc intake, immune suppression). Multivitamin-level zinc intake (8–15 mg daily) is safe and adequate for most. Higher doses (30–50 mg) should be time-limited and ideally guided by serum testing. For hair loss patients with risk factors for deficiency, vegetarian diet, malabsorption conditions, increased physiological demand, checking levels is reasonable. For general hair loss populations, dietary zinc adequacy is more important than supplementation.