Zinc is an essential trace mineral with multiple roles in hair follicle function — including enzyme activity, protein synthesis, and DNA replication in follicle cells. Zinc deficiency is associated with hair loss, and the relationship is well-established enough to make zinc testing a standard part of investigation in patients with unexplained shedding.
The mechanism is well-understood. Zinc is required for the activity of multiple enzymes involved in hair follicle cycling, including 5-alpha reductase (interestingly, zinc has some inhibitory activity on this enzyme, which is why zinc-containing shampoos have been studied as adjunct treatments in androgenetic alopecia). Zinc also supports the immune function that prevents inflammatory attack on follicles and the structural integrity of the hair shaft.
Clinical deficiency of zinc — serum zinc below the laboratory reference range — reliably causes diffuse hair shedding that resolves with supplementation. This is well-established and uncontested. The question for most patients is whether subclinical or borderline zinc status contributes to hair loss, and the evidence here is less certain.
For patients with unexplained diffuse hair loss, serum zinc measurement is a worthwhile investigation, particularly in those with restricted diets (vegetarians and vegans have lower zinc bioavailability from plant sources), high physical training demands, or gastrointestinal conditions that impair absorption.
Supplementation in confirmed deficiency: zinc sulphate 220mg daily (providing approximately 50mg elemental zinc) for a three-month trial is the standard approach. Zinc should not be taken in excess of requirements — high-dose zinc supplementation can impair copper absorption, causing secondary copper deficiency.
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