Genetically Reduced Vitamin D Levels Tied to Higher MS Risk

By Lorraine L Janeczko

NEW YORK - Genetically reduced 25-hydroxyvitamin D levels are associated with an increased risk for multiple sclerosis (MS), according to a new study.

"These findings suggest that individuals at high risk for MS, such as first-degree family members, should ensure that their vitamin D levels are normal," said senior author Dr. Brent Richards of McGill University in Montreal, Quebec, Canada.

"Vitamin D insufficiency is very common, and returning people to normal vitamin D levels can generally be achieved by taking vitamin D tablets, a relatively simple and safe intervention," he told Reuters Health by email.

The results came as a surprise, Dr. Richards said: "We and others have undertaken similar experiments to demonstrate that vitamin D is unlikely to play a role in coronary heart disease and type 2 diabetes, but these findings for MS are very strong statistically."

Earlier observational studies had found an association between lower vitamin D and greater MS risk, but it is not clear whether the relationship is causal.

To learn more, Dr. Richards and colleagues conducted a Mendelian randomization study, a genetic technique that reduces the likelihood of confounding or reverse causation. Their results appear in PLOS Medicine, online August 25.

The researchers first determined the effect of four single nucleotide polymorphisms (SNPs) on participants in the Canadian Multicentre Osteoporosis Study. The count of 25-hydroxyvitamin D (25(OH)D)-decreasing alleles across the four SNPs was very strongly associated with decreased 25(OH)D.

Using data from the International Multiple Sclerosis Genetics Consortium study, involving nearly 14,500 cases and more than 24,000 healthy controls, the team found that a genetic decrease of 1 standard deviation in the natural-log-transformed 25(OH)D was associated with two-fold greater odds of MS. Increasing 25(OH)D roughly 1.5-fold decreased the odds of MS by 50%.

In an editor's summary, Dr. Paolo Antonio Muraro of Imperial College London, United Kingdom, cautions that "the reliability of these findings may be limited by some of the assumptions made by the researchers during their analysis. Moreover, although these findings support a role for vitamin D in MS susceptibility, they provide no information about whether vitamin D modulates the course of MS after its onset, and they may not apply to people of non-European ancestry."

In an to Reuters Health, Dr. Muraro added, "Although the study does not directly demonstrate a causative role of vitamin D deficiency in MS, I personally consider it one of the strongest pieces of evidence supporting its implication and strengthening the case for a large randomized controlled trial of vitamin D supplementation aimed at reducing the incidence of MS."

Dr. Richards agreed, saying, "Our findings provide no insight into whether vitamin D can help people who already have MS. We don't know when vitamin D should be given and at what dose and for how long to prevent MS."

SOURCE: https://bit.ly/1Q8vqx5

PLOS Med 2015.

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