Vitamin D Levels During Pregnancy Could Affect Child IQ, Study Shows

pregnant woman relaxing outside


Key Takeaways

  • Vitamin D deficiency during pregnancy may impact the cognitive development of your child.
  • Women with darker skin tones are more at risk of vitamin D deficiency.
  • It may be necessary to discuss supplementation with your healthcare provider.

A direct correlation has been found between a child's IQ and their mother's vitamin D levels in pregnancy. It is understood that Vitamin D is necessary for fetal brain development, but researchers have now extended research to look at the cognitive development of offspring when they reach early childhood.

IQ levels in early childhood are considered stable and may have subsequent impacts on future schooling, health, and socioeconomic standing. Thus, researchers stress the importance of testing for vitamin D levels in pregnancy and supplementing if required.

The study also found that vitamin D deficiency was alarmingly common among pregnant women in general, but deficiency occurred at an even greater rate among women with darker skin.

What the Study Shows

The study, published in The Journal of Nutrition, looked at data from over 1000 women during pregnancy to determine their vitamin D plasma levels in the second trimester. Their children were followed up at 4-6 years of age and underwent a specialized child IQ test.

Lead researcher and study author, Melissa Melough reports that results showed that the higher a woman's vitamin D level in pregnancy was, the higher their child's IQ was when tested. According to Melough, these results suggest that “prenatal vitamin D status is an important predictor of a child’s cognitive development”.

The study also revealed that almost half of all women in the study were deficient in vitamin D and that it was more prevalent in women with darker skin.

Melough explains, “Vitamin D deficiency is very common, and those with pigmented skin are at greater risk. Melanin pigment protects the skin against damaging UV rays, but also blocks the production of vitamin D in the skin.”

How Does Skin Color Impact Vitamin D?

When the skin absorbs ultraviolet B (UVB) rays from sunlight, the body begins a cascade of hormonal and chemical reactions to turn the UVB into a usable form of vitamin D. The first step in this process involves a chemical known as 7-dehydrocholesterol. The reason skin color matters is because this chemical is also required by melanin.

Melanin is the name given to the pigment that creates color in the skin. The more melanin you have, the darker your skin color. If more melanin is present to absorb UVB and use the 7-dehydrocholesterol for its own use, there is little UVB left available for vitamin D production.

Hence, people with darker skin are more likely to be deficient in vitamin D.

Why Vitamin D Is Necessary for Brain Development

Vitamin D is commonly known for its role in bone strength, but this study adds to a growing body of research that indicates vitamin D is also necessary for neurodevelopment and cognitive function.

Registered dietitian Claire Virga explains that vitamin D is important beyond pregnancy. Children and adolescents need ongoing vitamin D for growth and learning.

Claire Virga, MS, RDN, CDN.

In addition to supporting learning, memory and motor control development, vitamin D plays a role in many other aspects of health important to childhood and beyond.

— Claire Virga, MS, RDN, CDN.

“In addition to supporting learning, memory and motor control development, vitamin D plays a role in many other aspects of health important to childhood and beyond,” says Virga.

She goes on to explain that beyond its role in cognition, “vitamin D deficiencies are associated with an increased risk for mental illness including depression. Vitamin D also modulates the immune system by reducing inflammation, which not only reduces the risk of acute infection but also reduces the risk for chronic inflammatory conditions.”

Does IQ at Ages 4-6 Really Matter?

At ages 4-6 years, a child has their whole schooling life ahead of them, and thus, it may be questioned if an IQ test so early in life really means much to their overall success in life.

Melough points out that “IQ tends to be fairly stable from preschool age into adulthood, and stability increases with age.”

Although she does declare that more research is still needed in the field, IQ is important to consider. It is not just about being a little smarter. She explains that IQ status impacts so many things in a child's life.

“Some observational studies have shown that IQ is positively associated with income, health, and even longevity. Importantly, these types of studies can’t establish a causal relationship, but they indicate that higher IQ could be advantageous.”

How Can You Boost Your Vitamin D Levels?

Virga explains that although vitamin D is not found widely in most food sources, there are a few good options available.

“Good food sources include fatty fish (like salmon, herring, mackerel and sardines), egg yolks, wild mushrooms (commercially grown mushrooms are usually grown in the dark and therefore do not contain much if any vitamin D) and fortified foods like some milks, orange juice and cereals," she says.

Supplementation of vitamin D is also an option, particularly if you don’t regularly consume the foods listed above. Melough explains that because fetal brain development begins so early in pregnancy, it would be beneficial for women to consider vitamin D supplementation with their usual pregnancy vitamins.

However, she explains that if you are at a higher risk of deficiency, chatting to your doctor is recommended because you may need supplementation above the standard recommendations.

“Women with pigmented skin and those who get little sun exposure should consult with their healthcare providers to determine if they could be deficient and if vitamin D supplementation beyond their prenatal vitamin is needed," Melough says.

Melissa Melough, PhD, RD

Women with pigmented skin and those who get little sun exposure should consult with their healthcare providers to determine if they could be deficient and if vitamin D supplementation beyond their prenatal vitamin is needed.

— Melissa Melough, PhD, RD

Where to Go From Here?

Further research in this area is warranted to ensure consistency in findings and to understand more about maternal vitamin D levels and the neurocognitive development of children.

However, with the information we do have, Melough says “I hope this research raises awareness about the high prevalence of vitamin D deficiency, especially among Black women, and leads to increased screening and treatment.”

What This Means For You

If you have darker skin, cover your skin when outdoors, or live in geographical locations that have low sunlight, it is important to have your vitamin D levels checked early in pregnancy and supplement as directed by your doctor.

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  1. Melough MM, Murphy LE, Graff JC, et al. Maternal plasma 25-Hydroxyvitamin D during gestation is positively associated with neurocognitive development in offspring at Age 4–6 Years. J Nutr. Published online 2020. doi:10.1093/jn/nxaa309

  2. D'Orazio J, Jarrett S, Amaro-Ortiz A, Scott T. UV radiation and the skinInt J Mol Sci. 2013;14(6):12222-12248. Published 2013 Jun 7. doi:10.3390/ijms140612222