The vitamin D controversy – Part 2

Abstract

Vitamin D has been implicated to play a role in multiple sclerosis (MS) since several reports showed that low vitamin D levels might increase the risk of MS and may contribute to disease progression. Vitamin D has been reported to regulate expression of the cytokine interleukin (IL)-17 which can play a key role in MS pathogenesis. Immunological effects of vitamin D administration have been explored in a few normal subjects could not be replicated with certainty in MS patients. This could be explained by vitamin D interaction with other components that modify MS such as seasonal variation, concomitant infection with EBV, estrogen signalling system, and therapy-induced changes in vitamin D metabolism. The utility of vitamin D level as a serological marker for disease activity has been assessed in several studies but the results were suboptimal due to small number of patients enrolled, and lack of correlation of vitamin D levels with MS symptomatology. Similarly, the results of several studies assessing vitamin D supplementation were inconclusive. A recent meta-analysis revealed no significant association between high-dose vitamin D treatment and risk of MS relapses. The lack of supportive evidence could be due to methodological factors including the starting time of supplementation during disease course, vitamin D doses and formulation, inclusion of patients with minimal disease activity, duration of the study, and concomitant use of disease modifying therapies. Hence, despite the observational evidence of the effect of vitamin D on MS course, there is a lack of high quality, large, randomized trials investigating whether vitamin D supplementation benefits people with MS.