Neonatal Vitamin D Levels Tied to Risk for MS
Investigators argue for “universal supplementation in pregnancy”
by Molly Walker
Staff Writer, MedPage Today
November 30, 2016
Infants with lower levels of vitamin D at birth had an increased risk of developing multiple sclerosis (MS) into adulthood, an observational study found.
There was an inverse association between 25-hydroxyvitamin D (25(OH)D) levels and the risk of developing MS. A quintile analysis found that the risk decreased monotonically as vitamin D levels increased (OR for highest versus lowest quintile 0.53, 95% CI 0.36-0.78, P=0.001 for trend), reported Nete Munk Nielsen, MD, of Statens Serum Institut in Copenhagen, and colleagues.
For every 25 nmol/L increase in vitamin D levels, the risk of MS decreased by 30% (OR 0.70, 95% CI 0.57-0.84), the authors wrote in Neurology.
The role of vitamin D in MS is “incompletely understood,” the authors wrote, though they noted that it may have a neuroprotective effect because it modifies and regulates the production and release of neurotrophic factors, which support the growth, survival, and differentiation of neurons. They cited various studies that have suggested that low vitamin D levels may be linked to an increased risk of MS, including a recent randomized trial that examined variations in gene function.
However, Nielsen’s group acknowledged that “some controversy exists” over whether this extends to vitamin D levels in utero. While various studies have suggested that patients with MS in the Northern hemisphere are more likely to be born in April or May, following very low winter vitamin D levels, other research has found mixed results.
Nielsen and colleagues found seasonal variation in vitamin D levels, with the lowest vitamin D levels observed for patients born in the spring. “More research is needed to confirm these results, but our results may provide important information to the ongoing debate about vitamin D for pregnant women,” Nielsen said in a statement.
The population-based case-control study examined dried blood spots samples from the Danish Newborn Screening Biobank for patients who were born after April 1981, and analyzed 521 patients with MS and 972 controls matched by sex and birth dates. Levels of vitamin D in the samples were measured using liquid chromatography tandem mass spectroscopy.
Overall, 26% of the U.S. population, and a third of pregnant women in Sweden, reported having less than optimal levels of vitamin D (<50 nmol/L), suggesting that an opportunity exists for prevention, wrote Ruth Ann Marrie, MD, of University of Manitoba in Canada, and Martin Daumer, PhD, of the Sylvia Lawry Centre for Multiple Sclerosis Research in Germany in an accompanying editorial. They argued for the need for additional vitamin D supplementation during pregnancy. "We can still aim to ensure pregnant women achieve the minimum levels of [vitamin D] that are considered important for health (i.e., >50 nmol/L),” the editorialists wrote. “Further study, including population-level surveillance of outcomes after supplementation is implemented, will tell us if higher target levels are needed.”
Marrie told MedPage Today in an email that it was important for clinicians on a practice level to educate their patients about the potential prevention of some chronic illnesses by achieving optimal vitamin D levels, even if patients were already taking prenatal vitamins.
“For many individuals, given the variation in 25(OH)D levels in the population and variable response to supplementation, this may require more vitamin D supplementation than is currently available in prenatal vitamins,” she said.
On a population level, Marrie added that “it would be important for relevant societies to provide guidelines, for government bodies to make recommendations, and for there to be public health programs to educate the public about the relationship between vitamin D and the risk of MS, and how the risk of MS could be reduced.”
Nielsen’s group concluded that their results provided “a rationale for universal vitamin D supplementation in pregnancy.” But they also noted that controls had significantly higher mean levels of vitamin D as adults than patients with MS (35.9 nmol/L versus 33.0 nmol/L, respectively, P<0.01), so they could not rule out higher levels of vitamin D in childhood, and early adulthood, as a potential confounder for "the apparent protective effects of in utero" vitamin D. The authors also noted that because the majority of patients were born after 1981, their findings would not be applicable to patients who develop MS later in life. And the study did not account for potential confounders including outdoor activity, diet, smoking status, or post-childhood supplement use.