Biotin is a water-soluble B vitamin that provides support for healthy hair, skin and nails. It stimulates differentiation of the epidermis and promotes the production of keratins. These proteins provide support to epithelial cells and are critical in maintaining the structure of skin, hair and nails. Clinical studies also indicate that biotin may adjust the cellular arrangement of the nail bed, helping to reinforce the keratin structure, promote strength and thickness, and reduce splitting. Biotin is also an essential co-factor for a number of metabolic carboxylation reactions, including carbohydrate, fat and protein metabolism. Recent studies have expanded biotin’s metabolic role, indicating that the vitamin maintains healthy genetic expression of the many enzymes for which it is a cofactor. For example, biotin may act to promote transcription and translation of glucokinase, an enzyme found in the liver and pancreas that participates in the metabolism of the carbohydrate glucose to form glycogen.