Many researchers have speculated that there must be a link between Vitamin D and multiple sclerosis (MS) based on the distribution of cases at certain latitudes. There are increased numbers of MS cases in areas that don’t get as much sunlight, and thus residents of those areas are more likely to have lower vitamin D levels.[ref][ref]
MS is an autoimmune disease that is thought to be caused partially by genetics and partially by environmental factors. Genetically, susceptibility to multiple sclerosis has been linked to quite a few different genes that give a slight increase to the risk, but one that stands out as a strong risk factor is in the HLA family of genes. The HLA genes code for the major histocompatibility complex (MHC) proteins that are an integral part of our immune system.
HLA-DRB1*1501 is a variant that is linked to a higher risk of MS, with studies estimating that people who are homozygous for HLA-DRB1*1501 have up to 6 times the normal risk for MS.
This ties into vitamin D levels because vitamin D regulates the expression of HLA-DRB1. From a 2009 study on the topic: “It was found that vitamin D specifically interacts with HLA-DRB1*1501 to influence its expression. This study therefore provides more direct support for the already strong epidemiological evidence implicating sunlight and vitamin D in the determination of MS risk, and implies that vitamin D supplementation at critical time periods may be key to disease prevention.” [ref]
If you have genetic data from someplace like 23andMe or AncestryDNA, HLA-DRB1*1501 type corresponds to rs3135388 – the A allele.[ref]
Check your 23andMe results for rs3135388 (v4, v5):
My take away: If you are at an increased risk for MS due to the HLA-DRB1*1501 haplotype, you may want to get your Vitamin D levels checked. Read more from the Vitamin D Council on how to get your daily D. Note that there are 15 other SNPs also thought to be associated in some way with Multiple Sclerosis.