Evidence for an Association Between Vitamin D and Multiple Sclerosis.

The cause of MS remains unknown, but a number of genetic and environmental risk factors, and their interactions, are thought to contribute to disease risk. A substantial evidence base now exists supporting an association between vitamin D and MS, primarily illustrated by a latitudinal gradient of MS prevalence, a month of birth effect, an interaction of vitamin D with MS-associated genes and the fact that high vitamin D levels have been associated with a reduced MS risk in longitudinal prospective work. The association is primarily based on epidemiological studies which renders the more elusive question of whether this association truly represents causation, or indeed reverse causality in the light of a potentially uncharacterised pro-dromal phase of the disease. The prospect of vitamin D supplementation preventing MS is a very attractive notion, but a number of areas of inconsistencies and unanswered questions exist. Most notably, future work will need to establish appropriate dosing, timing and method of vitamin D supplementation in optimising any potential clinical benefit. In this chapter, we discuss the strong epidemiological and growing mechanistic evidence supporting an association between vitamin D and MS, and aim to highlight areas of current debate and where future efforts would be well worth targeting. Given that MS is currently the most common, and a rising, cause of neurological disability in young adults in the Western world, elucidating the relationship between vitamin D and MS is a necessary priority in aiming to further develop therapeutic and preventative strategies against this disease.