High levels of vitamin D among pregnant women are associated with reduced risk of developing MS later

Previous studies suggest that the level of vitamin D in a person’s blood may influence the risk of developing MS. 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. [Salzer J, Hallmans G, Nyström M, Stenlund H, Wadell G, Sundström P. Neurology. 2012 Nov 20;79(21):2140-5. doi: 10.1212/WNL.0b013e3182752ea8.]

The 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.

What do these findings mean: 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. Additional studies of vitamin D in MS are ongoing.

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.

Source: National MS Society