Vitamin D Deficiency and Possible Role in Multiple Sclerosis

Vitamin D is not only an essential nutrient for bone homeostasis but has also been implicated in many other disorders including cardiovascular disease (CVD) and autoimmune diseases. Here we review the problem of vitamin D deficiency and guidelines to help achieve adequate levels in both the general population and in multiple sclerosis (MS) patients and its role in MS and impact on treatment. Although there is a lack of consensus on vitamin D deficiency and insufficiency, they have been defined as a serum level of 25(OH)D <50 nmol/L or 52.5–72.5 nmol/L, respectively. Deficiency is common in all age groups. Vitamin D is probably involved in the prevention of a number of disease states and 25(OH)D is thought to regulate at least 2,000 genes. Vitamin D toxicity is very rare, with none seen at doses up to 20,000 IU/day. However, the majority of primary care clinicians are not aware of the recommended dose for vitamin D supplementation and optimum serum level in terms of patients with MS. Several organisations have concluded that vitamin D screening cannot be recommended in the general population. Guidelines have been published on treatment and prevention of vitamin D deficiency, particularly for at-risk groups and during pregnancy. There is much evidence for the protective effects of vitamin D in MS. A higher level of sun exposure and intake of vitamin D as well as of serum 25 (OH)D, are associated with a lower risk of MS. It also has a beneficial effect on the clinical course of MS, such as lowering the risk of relapses. Growing evidence indicates that the effects of interferon-beta are additively enhanced by 25(OH)D in MS and this may be due to its modulating vitamin D metabolism.