Vitamin D has stong immunoregulatory properties, and suplementation prevents EAE, the MS-type disease introduced in animals. Examination of a large-scale population study has revealed intake of vitamin D supplements to be associated with a 40% reduced risk of developing MS (Munger et al 2004).
Sunlight exposure increases vitamin D levels, and people living in high latitudes in the northern hemisphere can suffer from a deficiency at certain times of the year if there is low intake in their diet. Munger et al point to low levels of vitamin D in MS patients and a correlation between low levels of vitamin D and increased lesion activity. New myelin sheath lesions most frequently occur in Spring when storage of vitamin D is at its lowest (Schwarz & Lewelling 2005).