Study shows maternal vitamin D linked to child IQ, finds disparities among black women

Optimal nutrition during pregnancy is crucial, as a mother is not just responsible for her own health, but also that of her developing fetus. Over the years, research has found that vitamin D status during pregnancy plays an integral role beyond just calcium and bone health. We now know that a mother’s vitamin D supply is passed to her baby in utero to help regulate important processes — including brain development.

The study

Fresh research published in The Journal of Nutrition pulled data from the CANDLE (Conditions Affecting Neurocognitive Development and Learning in Early Childhood) cohort, which included 1,503 women in their second trimester between 2006 and 2011. CANDLE researchers recruited pregnant women in Tennessee to join the study in 2006 and collected information over time about their children’s health and development.

Inclusion criteria for the vitamin D analysis included IQ data and availability of 25(OH)D data, commonly used to assess vitamin D status.

The researchers compared the vitamin D status to Stanford-Binet IQ scores in the offspring at 4–6 years old using multivariable linear regression and they also explored whether associations differed by race.

Findings

The authors concluded, “Second-trimester maternal 25(OH)D was positively associated with IQ at 4–6 y, suggesting that gestational vitamin D status may be an important predictor of neurocognitive development. These findings may help inform prenatal nutrition recommendations and may be especially relevant for Black and other dark-skinned women at high risk of vitamin D deficiency.”

About 46% of the mothers in the study were deficient in vitamin D during their pregnancy, and vitamin D levels were lower among Black women compared to White women.

Melissa Melough, the lead author of the study and research scientist in the Department of Child Health, Behavior, and Development at Seattle Children’s Research Institute, said while vitamin D deficiency is common among the general population and pregnant women, Black women are at a heightened risk. Melough added that she hopes the study will put a spotlight on the challenge so that health care providers can better address disparities among women of color.

Disparities

“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,” Melough said. “I hope our work brings greater awareness to this problem, which 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. 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.”

Looking beyond the study, Melough said that as many as 80% of Black pregnant women in the US may be Vitamin D deficient.

Although observational studies like this one cannot prove causation, Melough believes her findings have important implications and warrant further research.

An easy fix

Melough said even though vitamin D deficiency is quite prevalent, “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.”

When it comes to vitamin D consumed through food, it is one of the most challenging nutrients to obtain from diets. The recommended daily intake of vitamin D is 600 IU and on average, Americans consume less than 200 IU in their diet. Melough cautioned people will likely become deficient if they don’t make up for that gap through sun exposure or supplementation.

Further research is needed to determine the optimal levels of vitamin D in pregnancy, but Melough hopes 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.

Melough noted three key takeaways from the study:

Vitamin D deficiency is common during pregnancy, and Black women are at greater risk because melanin pigment in the skin reduces production of vitamin D

Higher vitamin D levels among mothers during pregnancy may promote brain development and lead to higher childhood IQ scores

Screening and nutritional supplementation may correct vitamin D deficiency for those at high risk and promote cognitive function in offspring

“I want people to know that it’s a common problem and can affect children’s development,” Melough said. “Vitamin D deficiency can occur even if you eat a healthy diet. Sometimes it’s related to our lifestyles, skin pigmentation or other factors outside of our control.”