Maternal vitamin D levels during pregnancy are linked to the IQ of the child

During pregnancy, the unborn child is totally dependent on the mother’s vitamin D status. Vitamin D is primarily known for its role in supporting bone development. However, the vitamin is also of vital importance to the child’s brain, cognitive skills, and intelligence. According to a new, American study that is published in The Journal of Nutrition, this is why it is so important for pregnant women to have optimal vitamin D levels in their blood. The researchers point to the fact that vitamin D deficiencies are rather common and mention that they observed significantly lower blood levels of the nutrient in pregnant women of color. They hope their study can contribute to increased focus on the benefits of vitamin D supplementation in pregnancy.

Today, vitamin D is viewed as a steroid hormone with particularly great influence on the brain and nervous system. During pregnancy, the fetus is totally dependent on the mother’s vitamin D status, and the nutrient is transferred via the placenta. After that, vitamin D crosses the fetal blood-brain barrier and then takes part in a host of different functions that are important for the structure and function of the brain. This is why vitamin D is so important for brain health and for the child’s cognitive development.

Lack of vitamin D is common among pregnant women – especially women of color

The sun is our main source of vitamin D, which we synthesize in our skin. During the winter period, however, the sun sits very low in the sky at our latitudes and that limits our vitamin D synthesis. Other factors that affect vitamin D status are things like lifestyle and skin type.
According to lead investigator Melissa Melough from Seattle Children’s Research in the United States, vitamin D deficiencies are widespread among Americans and among pregnant women. The risk seems to be the greatest among Afro-American women and others with dark skin, which is due to the fact that skin pigmentation, besides protecting against the sun’s UV rays, has a limiting effect on the skin’s vitamin D synthesis. The study showed that 46 percent of the participants lacked vitamin D during their pregnancy. According to Melough, up to 80 percent of black American people lack the nutrient.

The link between vitamin D status in pregnancy and the child’s IQ

Melough and her colleagues gathered data from a large population study in Tennessee called CANDLE (Conditions Affecting Neurocognitive Development and Learning in Early Childhood). The CANDLE study was initiated in 2006 and included 1,503 pregnant women and in their second trimester of pregnancy. Later, the scientists collected data about the children’s health and development. After adjusting for several confounding factors that can influence the IQ of the children, Melough found that higher blood levels of vitamin D during pregnancy was related to higher IQ in children aged 4-6 years. Still, Melough calls for more studies to find out what optimal levels of vitamin D in the blood during pregnancy should be.

The good news and more focus on vulnerable groups

Although it can be difficult to get enough vitamin D from the diet and from sun exposure, and even though lack of vitamin D is widespread, Melough points to the fact that vitamin D supplements constitute a simple and inexpensive solution. She hopes that the study will contribute to the development of new vitamin D recommendations for pregnant women, especially with regard to black Americans and other people at increased risk of vitamin D deficiency. She explains that vitamin D deficiency can easily occur in people who otherwise live healthily, simply because it is related to so many other factors such as the latitude at which you live, your skin type, your lifestyle etc. The study contributes with the following key information:

• Lack of vitamin D is common among pregnant women, and women of color have a greater risk of being vitamin D-deficient
• Having higher levels of vitamin D in the blood contributes to the development of the child’s brain and may help the child to higher scores in IQ tests
• Blood samples and vitamin D supplements can be used to correct vitamin D deficiencies among those people where deficiencies are commonhat can potentially improve the children’s cognitive development

Official recommendations for vitamin D

In the United States, the official vitamin D recommendations for adults are 15 micrograms per day. The average dietary intake of vitamin D is less than 5 micrograms, which is also the case in Denmark. The Danish Veterinary and Food Administration currently advises all adults to take a 5-10 microgram supplement daily during the winter period from October to April. This may help prevent a vitamin D deficiency before conception.
Also, the Danish Veterinary and Food Administration advises pregnant women to take a daily 10-microgram supplement all year round. The same goes for people with dark skin, veiled people, and people who get too little sunlight. Still, many pregnant women forget to take vitamin D or do not do it systematically. It is therefore a good idea for expecting mothers to have their vitamin D levels checked – especially during winter and spring where you are most likely to be deficient. The recommendations vary from country to country and peoples’ need for vitamin D can also vary.

References:

Melissa M Melough et al. Maternal Plasma 25-Hydroxyvitamin D during Gestation Is positively Associated with Neurocognitive Development in Offspring at Age 4-6 Years. The Journal of Nutrition 2020

Alexander Muacevic and John R Adler: The Role of Vitamin D in Brain Health: A Mini Literature Review. Cureus 2018

Andrea L. Darling et al. Association between maternal vitamin status in pregnancy and neurodevelopmental outcomes in childhood: results from the Avon Longitudinal Study of Parents and Children. (ALSPAC) British Journal of Nutrition, 2017