Dietary supplements in dermatology: A review of the evidence for zinc, biotin, vitamin D, nicotinamide, and Polypodium.

Dietary supplements are commonly recommended by dermatologists in the treatment of skin, hair, and nail disorders. This review of oral over-the-counter supplement use in dermatology summarizes current evidence for the use of zinc, biotin, vitamin D, nicotinamide, and Polypodium in the management of common dermatologic disorders. Evidence for the safety and efficacy of these supplements is limited. Very few large-scale randomized controlled trials exist for these over-the-counter supplements, particularly biotin and Polypodium. The lack of standardized dosing and standardized outcome measures makes comparison across existing studies challenging, and the lack of adverse events reporting in the majority of studies limits analysis of supplement safety. The most promising evidence exists for the use of nicotinamide in preventing nonmelanoma skin cancers. There is some evidence for the role of vitamin D in decreasing melanoma risk and progression in some individuals and for the photoprotective role of Polypodium, although additional high-quality studies are needed to determine appropriate dosing. Current evidence is insufficient to recommend the use of biotin or zinc supplements in dermatology. Large-scale randomized controlled trials investigating safety and efficacy are needed before widespread incorporation of these oral supplements into the general practice of dermatology.