- Vitamin D is a type of hormone and a powerful mediator of immune function. The data documenting an association between low vitamin D and high MS risk, relapses, disability and CNS inflammation now appear to be strong, consistent and reproducible.
- Data from a number of lines of investigation suggest that vitamin D may be one underlying common factor that begins to make sense of the large body of data on the geographic distribution of susceptibility to MS, including the north-south gradient of distribution and the migration data indicating that where people live during the first fifteen years or so of life affects the incidence of the disease.
- Genetically, a link appears to exist between alterations in the genes involved in vitamin D hormone synthesis and the vitamin D hormone receptor to MS risk. The strongest genetic risk factor for MS is a specific gene (HLA DRB1*1501), whose activity appears to be influenced by vitamin D.
- A small study of 18 patients with RRMS published in early 2010 compared very high-dosage vitamin D3 (up to 40,000 IU daily versus supplementation with up to 4,000 IU). After one year, 38 percent of the control group (those not taking high-dose vitamin D3) had an increase in disability, versus only 8 percent of the treatment group.
- In another study, mice treated with vitamin D prior to the induction of EAE (an MS-like condition in animals) did not develop its symptoms. This is compared with a 100-percent incidence of symptom development in untreated mice.
- A study looked at the effect on MS of maternal vitamin D exposure during pregnancy. This study was conducted with a group of 35,794 nurses whose mothers participated in the Nurses' Mothers' Study. The findings were consistent with a protective effect of maternal milk and vitamin D intake on the risk of developing MS.
- Lower serum vitamin D3 levels have been associated with a substantially increased subsequent relapse rate in individuals with pediatric-onset MS or CIS. A clinical trial is needed to determine whether vitamin D supplementation might improve the course of the disease in these groups.
- An Australian study found that people with CIS had less cumulative skin damage caused by the sun than non-MS controls, suggesting that they had less sun exposure. In a Canadian study of children who had experienced a single neurologic episode, the 16 percent who went on to develop MS had significantly lower vitamin D levels than those who did not.
- Evidence is beginning to accumulate of a complex interaction between genetic susceptibility to MS and the role of vitamin D. The risk of developing MS is three times higher among those who carry a single copy of a specific gene variant and 10 times higher in those carrying two copies of the gene, which appears to be involved in the immune system. Proteins activated by vitamin D bind to and alter the function of a section of the chromosome near this gene, suggesting that vitamin D deficiency during pregnancy might alter the function of fetal genes, predisposing children to MS. The gene contains a "switch" that is activated by one form of vitamin D; this gene was missing from the variants not associated with MS.