Vitamin D and multiple sclerosis: what is the clinical impact?

Evidence for a causal role for vitamin D in multiple sclerosis (MS) is being gathered. Epidemiological, molecular and animal model studies have paved the way in our understanding of the effects of vitamin D in demyelinating disease. Several clinical trials have been completed and more are under way to understand the full extent and value of vitamin D supplementation on disease progression. Many questions remain unanswered however and careful study design is increasingly pertinent. Timing of exposure, dosage and transgenerational effects are some of the several important questions that need to be addressed. In this issue, Carlson and Rose highlight these points and provide a review of vitamin D and MS with an emphasis on the most recent clinical studies. Further evidence of vitamin D deficiency as a causal factor, its molecular targets in MS and its prospect as a therapeutic and preventative agent are questions that warrant further study.