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Children whose mothers had higher vitamin D levels during pregnancy scored better on tests of memory, attention and problem-solving skills at ages 7 to 12 compared with those whose mothers had lower levels. That is a key finding of a  that my colleagues and I published in The American Journal of Clinical Nutrition.

While vitamin D has long been known for its , scientists have since uncovered its importance in  and . Now, growing evidence — including our new findings — suggest it may also support brain development beginning in the womb.

My team and I found that the link between prenatal vitamin D levels and childhood cognition was strongest among Black families, who .

This suggests that vitamin D supplementation may be a promising, low-cost strategy to support brain development while reducing racial disparities. Our study also suggested that vitamin D levels early in pregnancy may be most important for childhood cognitive development, highlighting the importance of early action by health care providers.

We analyzed more than 900 mother-child pairs across the U.S. who participated in a , short for Environmental influences on Child Health Outcomes. We measured vitamin D in the mothers’ blood during pregnancy and assessed children’s cognitive abilities using a standardized test battery. We also accounted for other important factors that shape childhood development such as the mother’s education, neighborhood conditions and the child’s age and sex.

This new study builds on our earlier findings that higher vitamin D levels during pregnancy are  in early childhood and with  in middle childhood.

Collectively, these studies suggest that vitamin D plays a crucial role in brain development during pregnancy, with lasting benefits for children’s cognitive and behavioral outcomes.

Why it matters

Vitamin D deficiency is a . 

In the U.S., about 42% of adults have , or ng/ml, a commonly used cutoff for deficiency. About  are deficient, and the rates are even higher among Black pregnant women, with . This racial difference is partly due to , as melanin pigment reduces the skin’s ability to produce vitamin D from sunlight.

Although we can get vitamin D both from sun exposure and our diets, deficiency is common because these sources don’t meet everyone’s needs. Sunlight isn’t always a reliable source, especially for people with darker skin, those living in northern climates or those who often wear sunscreen or sun-protective clothing. Natural food sources such as fatty fish, egg yolks and certain mushrooms contain some vitamin D, and  such as milk and breakfast cereals help, but not everyone eats enough of these foods to maintain healthy vitamin D levels. 

That’s why supplements are often necessary and are recommended in many cases by the .

Although current guidelines recommend that pregnant women consume  daily, higher doses of at least  are often needed to correct deficiency. On average, U.S. women consume  from food and beverages, and  . This highlights an important opportunity for clinicians to improve screening and support around vitamin D supplementation both before and during pregnancy.

If a simple, low-cost strategy such as prenatal vitamin D supplementation can help support brain development, it may yield lasting benefits for children. Long-term studies have shown that higher cognitive scores in childhood are linked to better , as well as .

What still isn’t known

While our studies have linked higher vitamin D levels in pregnancy to improved cognitive and behavioral development in children, we cannot yet prove that vitamin D is the direct cause. 

Therefore, studies called randomized controlled trials — the gold standard of research — are needed to confirm these findings and determine how best to translate them into clinical practice. These studies will be essential for determining the optimal target levels for vitamin D to support brain development in pregnancy.