Is supplemental vitamin D useful in the clinically isolated syndrome (CIS) typical of multiple sclerosis?

INTRODUCTION: Although vitamin D deficiency is a risk factor for multiple sclerosis (MS), vitamin D has only limited benefit in MS. It is now being considered in clinically isolated syndrome (CIS) prior to MS. AREAS COVERED: In the D-Lay MS clinical trial, supplemental vitamin D3 reduced disease activity in CIS and the early stages of relapsing-remitting (RR) MS without causing any serious adverse events. EXPERT OPINION: The race/ethnicity of participants is not given in D-Lay MS and should be included in future studies of vitamin D supplementation in CIS. It will be of interest to investigate the long-term effects of supplementation, initially given in CIS, on the disease and physical activity associated with the progression to RRMS. Interferon beta and teriflunomide are effective in CIS, and due to their different mechanisms of action to vitamin D, may have additive effects with the supplement. As vitamin D supplementation is associated with low or no adverse effects, this supplementation should be considered further in clinical trial and in real life treatment of CIS.