Vitamin D as a clinical biomarker in multiple sclerosis.

Introduction: Vitamin D has attracted a lot of attention in relation to multiple sclerosis (MS) and many other disorders; however, the evidence for a major role(s) for vitamin D in MS is compelling and multifactorial involving results from epidemiology, immunology, genetics, biochemistry and translational medicine.

Areas covered: Multiple studies that illustrate that insufficient levels of vitamin D not only contribute to the risk of getting MS but may also worsen disease progression for MS patients are discussed. Genetic evidence also implicates vitamin D as being important in MS since individuals are at greater risk of getting MS if they harbor a mutation in a gene responsible for vitamin D synthesis (25-hydroxylase). Other modifiers of MS disease appear to interact with the vitamin D receptor. The Epstein-Barr virus (EBV) is a risk factor for MS and may in part worsen disease through the interactions between one of its gene products (EBNA-3) and the vitamin D receptor to attenuate vitamin D-regulated genes. Retrospective studies have shown that higher vitamin D levels are associated with a significant improvement of clinical and magnetic resonance imaging outcomes. Increasing clinical observations are also indicating adverse effects of low vitamin D in MS.

Expert opinion: Mounting evidence from epidemiology, genetic, retrospective clinical studies and emerging basic science studies support a strong rationale for how vitamin D could be an important modifier of MS disease. Well-designed clinical trials are now ongoing and will provide further insight on how vitamin D supplementation may impact MS.