New Findings on Vitamin D and Multiple Sclerosis

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earchers have discovered new implications to the link between low vitamin D levels and multiple sclerosis (MS). A study published in PLOS Medicine on August 25, 2015, reports the results of research conducted by Lauren E. Mokry, and colleagues at McGill University, in Montreal, Canada. Although observational studies had demonstrated an association between low vitamin D levels and MS, it was not clear if the relationship was causal.

Although researchers already knew that decreased levels of vitamin D, or more specifically, 25OHD, the clinical determinant of vitamin D status, is related to MS, there was no evidence to show that the relationship was causal, confounding, or there was reverse causation. The use of a Mendelian randomization study ruled out confounding because gene variants are inherited randomly, and prevented reverse causation because MS does not change genetic variants.

Researchers first examined data from participants in the Canadian Mulitcentre Osteoporosis Study to determine the effect on 25OHD levels of four single nucleotide polymorphisms (SNPs). Next, the researchers used the SNPs to investigate the association between genetically lower 25OHD levels and MS. For this portion of the study, they used data from participants in the International Multiple Sclerosis Genetics Consortium study. The researchers found that “a genetic decrease in the natural-log-transformed 25OHD level by one standard deviation was associated with a 2-fold increased risk of MS.”

The implications of this study could have a positive impact. If a person who has a genetically lower 25OHD level could increase that level by 1.5 times, his or her chance of developing MS could decrease by as much as 50%, the researchers noted. However, there are limitations to the study results. For example, all of the participants in the International Multiple Sclerosis Genetics Consortium study were of European ancestry, so the results may not apply to those of non-European ancestry.

Additionally, while the results of this study show a strong association between lower 25OHD levels and susceptibility to MS, they do not show whether or not vitamin D can make any difference in the course of the disease after onset. More study is warranted, though, to investigate the impact of vitamin D supplements and the progression of MS.