Vitamin D levels during pregnancy associated with child brain development

Mothers' vitamin D levels during pregnancy may be associated with their children's IQ, according to a new study published in The Journal of Nutrition.

For the study, researchers used data from a cohort in Tennessee called the Conditions Affecting Neurocognitive Development and Learning in Early Childhood (CANDLE) study. CANDLE researchers recruited pregnant women to join the study starting in 2006 and collected information over time about their children's health and development.

After controlling for several other factors related to IQ, higher vitamin D levels in pregnancy were associated with higher IQ in children ages 4 to 6 years old. Although observational studies like this cannot prove causation, the researchers said they believe their findings have important implications and warrant further research.

The study also identified significantly lower levels of vitamin D among Black pregnant women. According to the researchers, as many as 80 percent of Black pregnant women in the U.S. may be deficient in vitamin D. Of the women who participated in the study, approximately 46 percent of the mothers were deficient in vitamin D during their pregnancy, and vitamin D levels were lower among Black women compared to White women, according to the study.

The recommended daily intake of vitamin D is 600 international units (IU). On average, Americans consume less than 200 IU in their diet, and so if people aren't making up that gap through sun exposure or supplementation, the researchers said people will probably become deficient. Foods that contain higher levels of vitamin D include fatty fish, eggs, and fortified sources like cow's milk and breakfast cereals. However, the researchers said that vitamin D is one of the most difficult nutrients to get in adequate amounts from our diets.

Additional research is needed to determine the optimal levels of vitamin D in pregnancy, but the researchers said they hope this study will help to develop nutritional recommendations for pregnant women. Especially among Black women and those at high risk for vitamin D deficiency, nutritional supplementation and screening may be an impactful strategy for reducing health disparities, they said.

"Vitamin D deficiency is quite prevalent," said Melissa Melough, RD, the lead author of the study and research scientist in the Department of Child Health, Behavior, and Development at Seattle Children's Research Institute, in a statement. "The good news is there is a relatively easy solution. It can be difficult to get adequate vitamin D through diet, and not everyone can make up for this gap through sun exposure, so a good solution is to take a supplement."