Previous Studies Suggest Level of Vitamin D in a Person’s Blood May Influence the Risk of Developing MS
November 20, 2012
In a newly published study, Jonatan Salzer, MD, and colleagues at Umeå University in Sweden confirmed that women who had higher levels of vitamin D during the first trimester of pregnancy had a lower risk of later developing MS than women with lower levels, while the vitamin D levels during early pregnancy did not impact their children’s chances of developing MS later on. Additional studies of vitamin D in MS are ongoing. The study was published in the November 20, 2012 issue of Neurology.
Background: Many factors, including genetic and environmental factors, probably affect the risk of developing MS. Vitamin D is an important nutrient that humans get from food, dietary supplements, and most importantly, from sun exposure. Research has increasingly indicated that lower levels of vitamin D in the blood are associated with a higher risk of developing MS. People who live in northern latitudes and who obtain little vitamin D from sun exposure in the winter have a higher risk of developing MS than people who live in lower latitudes.
Study: Dr. Salzer and colleagues analyzed blood samples that had been drawn from 164,000 people residing in northern Sweden, including 192 people who later developed MS, and 37 pregnant women whose children went on to develop MS later in life.
Levels of Vitamin D that are considered “sufficient” are controversial, but this study used a cut-off of 75 nmol/L. They classified the women as either vitamin D sufficient (levels in blood greater than or equal to 75 nmol/L) or insufficient (lower than 75 nmol/L). In this population vitamin D levels were generally low, and less than 10% of women had levels of vitamin D that were considered “sufficient.”
They found that women classified as having sufficient levels of vitamin D had a 61% decreased risk of developing MS compared to women with insufficient levels. (These results are likely to apply to men as well.) However they also found that the children of the women who had sufficient levels of vitamin D during the first trimester of pregnancy were not at lower risk of developing MS.
The investigators also reported that blood levels of vitamin D among people living in Nordic countries have decreased steadily from 1976 through 2005, which they suggest may help to explain the observed increase in cases of MS during the same period.
The study was supported by Biogen Idec, Merck Serono, the Swedish Association of Persons with Neurological Disabilities, Umeå University and the Västerbotten County Council.
Comment: Sufficient levels of vitamin D may help to lower the risk of MS, but there are other important factors that impact this risk, and it is not yet clear at what point in a person’s life vitamin D levels may play a role in MS risk. Although spring births have been associated with higher MS risk, possibly due to low levels of vitamin D during winter pregnancies, in this study, vitamin D sufficiency during the first trimester of pregnancy was not associated with a lower risk of developing MS among the offspring. The authors conclude that the most important time for vitamin D levels to impact MS risk may be between late pregnancy and young adulthood. However, the authors point out that the number of people analyzed in this study was small and vitamin D levels were generally low, making definitive conclusions difficult. In addition, exposure to sunlight may affect risk of MS not only through production of vitamin D, but also through other, as yet unknown ways.
The National MS Society is funding several projects in this area, including a clinical trial underway to test whether vitamin D can reduce disease activity in people who have MS. In 2011, the Society convened a summit to explore vitamin D trials farther.
Chronic excess vitamin D is associated with side effects, and some people cannot take supplements, so their use should be administered and monitored in consultation with a physician.