Vitamin D and multiple sclerosis

Multiple sclerosis (MS) is a genetically and immunologically complex neurodegenerative disease that often strikes in young adulthood and causes significant disability in individuals who are afflicted. Although there is no doubt that genetic risk factors and other environmental factors contribute to MS etiology, the evidence supporting an inverse association between vitamin D₃ and MS risk and severity is sufficiently strong and diverse to nearly satisfy the criteria for asserting that a causal relationship exists between insufficient vitamin D₃ and MS disease risk and severity. Vitamin D₃ and MS hypothesis provides a coherent explanation for several puzzling facts of MS natural history and biology in women. Specifically, this hypothesis provides some explanation as to why the disease course commonly shows a relapsing-remitting pattern that later becomes progressive, why there is a rapidly increasing female sex bias, and why the disease remits during pregnancy. Seasonal fluctuations in UVL and vitamin D supplies in high latitude regions may contribute to the relapsing-remitting pattern. Moreover, the emerging concept of synergy between the vitamin D₃ and E₂ endocrine systems suggests that increasing prevalence of vitamin D insufficiency may adversely affect women more than men, contributing to the growing female sex bias. The increases in estriol and 1,25(OH)₂D₃ during pregnancy may reduce MS disease activity, whereas the decreases in E₂ production at menopause may undermine the vitamin D₃ protective effects and accelerate MS disease. These insights are banked upon to suggest new approaches to alter the MS disease course in women.