Considerations on vitamin D supplementation in multiple sclerosis

Vitamin D is the precursor of a steroid hormone with immune-modulating properties. Low circulating levels of the vitamin D metabolite 25-hydroxyvitamin D have been associated with a higher risk of disease activity in patients suffering from multiple sclerosis (MS), in terms of relapse risk and risk of MRI lesions. Additionally, several randomized controlled clinical trials, although mostly negative on primary endpoints, provided some indications for positive effects of vitamin D supplements on these endpoints. However, results of individual association studies and trials in MS are heterogeneous. In this chapter, we provide a discussion of these different studies. We explore several explanations for this heterogeneity and conclude with some implications for advises on vitamin D supplements for people with MS.