Nutrition and nail disease.

The nail is a specialized keratinous skin appendage that is often overlooked, even though nail disorders comprise approximately 10% of all dermatologic conditions. We provide an overview on the basic anatomy of the nail and function of each structure. We examine the chemical profile, including the keratin and mineral composition, of the nail plate. Subsequently, nail manifestations are reviewed, as virtually every nutritional deficiency can affect nail growth in some manner. We focus on how each nutritional deficiency can affect the different anatomic structures of the nail unit. The terminology and the differential diagnoses of the many different nail plate and nail bed abnormalities are reviewed. Finally, we focus on the evidence behind nutrition-based treatments in the setting of several nail disorders.