Vitamin D and multiple sclerosis: an update Margherita T Cantorna Observational studies document a positive relationship between vitamin D from the environment (sunlight or diet), circulating vitamin D status, and improved symptoms or prevention of multiple sclerosis (MS). Experimental animal models of MS reproduce the beneficial effects of vitamin D and 1,25(OH) 2 D 3 . The geographical distribution of MS can be explained by both the hygiene hypothesis and the vitamin D hypothesis. It therefore seems more likely that both hypotheses may be correct and that there are interactions between multiple environmental factors like vitamin D and the rate of infection that might explain the etiology of MS. The effects of vitamin D on the immune system and in the CNS have begun to be described and there is some information on the mechanisms underlying the effects of vitamin D in MS. A need exists for better understanding of the interactions of the environmental factors on MS, communication with the physicians treating MS patients as to the benefits of vitamin D, and clinical interventions with both vitamin D and analogs of 1,25(OH) 2 D 3 . © 2008 International Life Sciences Institute INTRODUCTION Although classified as a vitamin, vitamin D is not a true vitamin since significant amounts of vitamin D are made in the skin in association with sunlight exposure. The amount of vitamin D made as a result of sunlight expo- sure depends on a number of factors including skin pig- mentation, age, latitude, season, and sunscreen use. Since the sun is an unreliable and difficult to control source of vitamin D, it seems to be inadequate or unreasonable to suggest that vitamin D should be obtained exclusively by exposure to sunlight. There are problems with obtaining vitamin D from the diet as well since, except for in some fish, very little vitamin D is present naturally in the food supply. Nonetheless, vitamin D from either sunlight or diet has been hypothesized to be an important environ- mental factor that affects the development of a number of chronic diseases including autoimmune diseases like multiple sclerosis (MS) and cancers, especially prostate cancer. GENES, THE ENVIRONMENT, AND MS MS is an autoimmune disease of the central nervous system that is of unknown etiology and affects more women than men (2:1 ratio). A number of risk factors for MS have been identified and they can loosely be put into one of two categories – genetic or environmental compo- nents. 1,2 Highlighting the role of genetics in the disease is that family members of MS patients are at an increased (20–40%) risk of developing MS and monozygotic twins are at a further increased (additional 10%) risk of devel- oping MS. However, the concordance rate in identical twins is only 25% for MS. Therefore, even though the twins are genetically identical, 75% of the time only one twin develops MS. The environmental factor(s) that explain this anomaly have been difficult to identify and are, therefore, still largely undocumented. Mapping the distribution of MS reveals it is most prevalent in the northern United States, Canada, and the northern parts of Western Europe. Studies that look at populations Affiliation: MT Cantorna is with the Center for Immunology and Infectious Disease, Department of Veterinary and Biomedical Science, The Pennsylvania State University, University Park, Pennsylvania, USA. Correspondence: MT Cantorna, Department of Veterinary and Biomedical Sciences, The Center for Molecular Immunology and Infectious Disease, 115 Henning Bldg., University Park, PA 16802, USA. E-mail: mxc69@psu.edu, Phone: +1-814-863-2819, Fax: +1-814-863-6140. Key words: hygiene hypothesis, multiple sclerosis, vitamin D doi:10.1111/j.1753-4887.2008.00097.x Nutrition Reviews® Vol. 66(Suppl. 2):S135–S138 S135 Downloaded from https://academic.oup.com/nutritionreviews/article/66/suppl_2/S135/1855150 by guest on 13 June 2022