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NMU – 180 Maternal Vitamin D Level Impacts Child’s IQ at Ages 4-6 yr

Nutrition/Natural Medicine Update No 180 (November 3, 2020)

with Dr. James Meschino


Topic: Maternal Vitamin D Level Impacts Child’s IQ at Ages 4-6 yr.

Source: Journal of Nutrition (November 2020)


An important study was published in the Journal of Nutrition in November 2020. In agreement with previous studies of this nature, the researchers showed that a mother’s vitamin D blood level during the second trimester of pregnancy has a significant impact on her child’s IQ measured at 4-6 years of age. This should not be a surprise, as the mammalian brain has vitamin D receptors by the 12th day after conception, and the developing fetal brain requires vitamin D for many aspects of brain development to occur. As the researchers stated, “maternal vitamin D is transported through the placenta, and by binding to vitamin D receptors in the fetal brain, it exerts transcriptional control over many genes related to structural brain development”.

This study used data from the famous CANDLE Study (Conditions Affecting Neurocognitive Development and Learning in Early Childhood), which included assessing the maternal vitamin D blood level of over 1500 pregnant women in their second trimester of a healthy pregnancy whereby only a single fetus was present (no twins or triplets etc.). The study clearly showed that the higher the maternal blood level of vitamin D in the second trimester of pregnancy, the higher was the child’s IQ, as well as verbal and non-verbal IQ at ages 4-6 years of age.

Alarmingly, the study showed that 46% of pregnant women who participated in the study had deficient levels of vitamin D in their blood. This was a U.S.-based study. Vitamin D deficiency is indicated by a blood level below 20 ng/ml (50 nmol/L), as this value was established to help ensure adequate bone health. However, this level of vitamin D may not necessarily be high enough to ensure optimal fetal brain development or to help prevent the development of cancer, diabetes, Alzheimer’s disease or to ward off other diseases that may be impacted by suboptimal vitamin D blood levels, according to emerging studies. Black American women appear to be most prone to vitamin D deficiency, as their average vitamin D blood level in this study was only 19.8 ng/ml (49.5 nmol/L). Caucasian women had an average vitamin D blood level of 25.9 ng/ml (62.5 nmol/L). According to lead researcher Melissa Melough, as many as 80% of Black pregnant women in the U.S. may be deficient in vitamin D. In fact, according to the researchers, vitamin D deficiency is a worldwide problem affecting the general public and women of childbearing age, especially among those with darker skin. This is because darker-skinned individuals have more melanin pigment in the skin, which acts as a barrier to ultra-violet light, decreasing its ability to penetrate the skin and stimulate the production of vitamin D within skin cells. U.S. based data from 2001–2006 indicated that 13% of White pregnant women in the United States were deficient in vitamin D compared with 80% of pregnant Black women.

In this study, race was not a factor. Regardless of skin colour, the higher the mother’s blood vitamin D level during the second trimester of pregnancy, the higher was the child’s IQ at ages 4-6 yrs. More specifically, every 10 ng/mL (25 nmol/l) increase in maternal vitamin D blood levels was associated with a 1.17-point higher Full-Scale IQ in the child as well as a 1.17- point higher Verbal IQ, and a 1.03-point higher Nonverbal IQ. The researchers point out that the observed effect size of 1.17-point IQ score per every 10 ng/mL increase in the mother’s vitamin D blood level may translate into other meaningful positive future outcomes.  It has been estimated that for each IQ point decrement, males experience a 1.93% decrease in lifetime earnings and females experience a 3.23% decrease in lifetime earnings. Observational studies have also linked low perinatal and prenatal vitamin D maternal blood levels with developmental disorders, including schizophrenia and autism.

The researchers conclude that the recommended vitamin D intake level during pregnancy is likely too low.  They state, “popular prenatal supplements, which typically contain 400–600 IU vitamin D, are likely insufficient to correct vitamin D deficiencies (which are very common across the population). Randomized controlled trials have suggested that daily supplementation of 800 to 1000 IU may be needed for repletion in pregnancy and that doses as high as 4000 IU may be ideal in cases of severe deficiency. Importantly, there is currently no established consensus regarding optimal vitamin D concentrations during pregnancy, and additional research in diverse populations is needed to develop guidelines, which may need to be population-specific, for treating deficiency during pregnancy.” In the meantime, I think it is important for all women who are pregnant or who are planning to become pregnant to know what their blood vitamin D level is. From an overall health perspective, the evidence suggests that a blood vitamin D level between 30 ng/mL (75 nmol/L) and 50 ng/mL (125 nmol/L) is a good target to aim for.

I’ve included the reference for this study in the text below.


Melissa M Melough, Laura E Murphy, J Carolyn Graff, Karen J Derefinko, Kaja Z LeWinn, Nicole R Bush, Daniel A Enquobahrie, Christine T Loftus, Mehmet Kocak, Sheela Sathyanarayana, Frances A Tylavsky. 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.


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