Vitamin D and multiple sclerosis: an update

Vitamin D and its biologically active metabolite, 1-alpha, 25dihydroxyvitamin D3 [1,25(OH)2D3], which is produced in the dermal skin layer after exposure to ultraviolet (UV) radiation, play a central role in calcium metabolism and bone homeostasis; besides this "classical'' function, they hold also other important activities, such as the regulation and differentiation of normal and tumoral cellular proliferation, and a powerful immunomodulatory activity. The relationship between vitamin D and multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system (CNS) with multifactorial pathogenesis, involves various aspects, including first of all the presence of an altered bone metabolism in subjects affected by the disease. On the basis of epidemiological data of prevalence, vitamin D and sunlight exposure may play a protective role in MS development. Nevertheless, the possible disease-modifying effect of a supplementation with vitamin D and its analogues requires further investigation, as current evidence does not support its recommendation in the specific treatment of the disease.