Seattle, WA—Vitamin D levels during pregnancy have been linked with the child’s IQ,according to a new studyfrom the Seattle Children’s Research Institute (SCRI).

A mother’s vitamin D supply is passed to the fetus in utero, a press release explains, where it helps regulate processes including brain development. The researchers used data from a cohort in Tennessee called the Conditions Affecting Neurocognitive Development and Learning in Early Childhood (CANDLE) study, which recruited pregnant women beginning 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.

One major issue the study noted: Black women are at greater risk of vitamin D deficiency than white women, with up to 80% of Black pregnant women deficient in vitamin D. Melissa Melough, lead author of the study and research scientist in the Department of Child Health, Behavior, and Development at SCRI, explains: "Melanin pigment protects the skin against sun damage, but by blocking UV rays, melanin also reduces vitamin D production in the skin. Because of this, we weren't surprised to see high rates of vitamin D deficiency among Black pregnant women in our study. Even though many pregnant women take a prenatal vitamin, this may not correct an existing vitamin D deficiency.”

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Fatty fish, eggs, and fortified foods like cow’s milk and breakfast cereals are good sources of vitamin D, but Melough says in the press release that vitamin D is one of the most difficult nutrients to get in adequate amounts from the diet. "Vitamin D deficiency is quite prevalent," she said. "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."

Additional research is needed to determine the optimal levels of vitamin D during pregnancy, but Melough hopes the study will help develop nutritional recommendations for pregnant women and promote nutritional supplementation and screening during pregnancy.

The press release notes that this is an observational study, and therefore cannot determine causation.

That said, Melough thinks the work is useful. "I hope our work brings greater awareness to this problem, shows the long-lasting implications of prenatal vitamin D for the child and their neurocognitive development, and highlights that there are certain groups providers should be paying closer attention to,” she said. “Wide-spread testing of vitamin D levels is not generally recommended, but I think health care providers should be looking out for those who are at higher risk, including Black women."