Plain language summary
Vitamin D is associated with a reduced risk and severity of multiple sclerosis (MS). However, whether supplementing vitamin D level alters disease severity, is a matter of ongoing debate. This review looks at both clinical and pre-clinical evidence for supplementing vitamin D in people with MS. In vitro experiments show that vitamin D and its metabolites can alter function of various immune cells, mostly via interaction with vitamin D receptors (VDR). Results from human clinical trials, however, are mixed. Preclinical evidence suggests that high dose vitamin D supplementation, when leading to hypercalcaemia, a potentially serious side effect of excessive vitamin D intake, may worsen MS. The authors also review research which suggests mechanisms by which sun exposure can improve MS symptoms independent of vitamin D production. The authors conclude that moderate sun exposure, combined with adequate dietary intake of vitamin D, and in conjunction with a regular assessment of vitamin D serum levels (to avoid hypercalcaemia), might be the best strategy for patients with MS.
Abstract
The exact cause of multiple sclerosis (MS) remains elusive. Various factors, however, have been identified that increase an individual's risk of developing this central nervous system (CNS) demyelinating disease and are associated with an acceleration in disease severity. Besides genetic determinants, environmental factors are now established that influence MS, which is of enormous interest, as some of these contributing factors are relatively easy to change. In this regard, a low vitamin D status is associated with an elevated relapse frequency and worsened disease course in patients with MS. The most important question, however, is whether this association is causal or related. That supplementing vitamin D in MS is of direct therapeutic benefit, is still a matter of debate. In this manuscript, we first review the potentially immune modulating mechanisms of vitamin D, followed by a summary of current and ongoing clinical trials intended to assess whether vitamin D supplementation positively influences the outcome of MS. Furthermore, we provide emerging evidence that excessive vitamin D treatment via the T cell-stimulating effect of secondary hypercalcemia, could have negative effects in CNS demyelinating disease. This jointly merges into the balancing concept of a therapeutic window of vitamin D in MS.
Methodological quality
Allocation concealment
:
Not applicable
