intelligence

The Importance Of Vitamin D During Pregnancy

Author: Dr. Stephen Chaney

As an expectant mother, you want the best for your child. You want them to be healthy and happy. You probably also want them to be smart.

Your doctor has recommended you take a prenatal supplement. You have probably heard about the importance of folic acid for a successful pregnancy. I have also written about the importance of adequate omega-3s and iodine during pregnancy for the cognitive development of your child.

But what about vitamin D? Vitamin D receptors are expressed in the mammalian brain as early as 12 days into gestation, and vitamin D is thought to be important in neurocognitive development.

Previous studies have shown that vitamin D deficiency during pregnancy is associated with delayed motor-skill and social development during the first few years of childhood. But it is uncertain whether these early deficits translate into long-term deficits in IQ and emotional stability.

This study was designed to answer that question by comparing blood 25-hydroxyvitamin D levels in the mother’s blood during the second trimester and IQ measurements of their children between the ages of 4 and 6.

How Was This Study Done?

This study used data from the CANDLE (Conditions Affecting Neurocognitive Development and Learning in Early Childhood) database. This portion of the study measured blood levels of 25-hydroxyvitamin D during the second trimester of pregnancy of 1503 women from the Memphis area of Tennessee. The 25-hydroxyvitamin D levels were compared with the IQ of their children measured between the ages of 4 and 6.

The average age of the mothers was 26 and 63% of them were black.

Of course, there are many other factors that influence mental development during childhood. Accordingly, the data were corrected for the overall quality of the maternal diet, maternal IQ, maternal education, maternal age, marital status, BMI (a measure of obesity), tobacco use during pregnancy, alcohol use during pregnancy, and household income.

Does Vitamin D Affect IQ?

Here are the results from the study:

• The average blood level of 25-hydroxyvitamin D at week 23 of pregnancy was 21.6 ng/mL.

• • 45.6% of the women were vitamin D deficient (<20 ng/mL 25-hydroxyvitamin D).

• The average blood level of 25-hydroxyvitamin D in this study was 19.8 ng/mL for Black women and 25.9 ng/mL for White women.

• • This is consistent with a previous report that 80% of Black pregnant women in this country are vitamin D deficient compared to only 13% of White pregnant women.

• After adjusting for other variables known to affect IQ, every 10ng/mL increase in 25-hydroxyvitamin D status during pregnancy resulted in an increase of:

• • 1.17 points in overall IQ.

• • 1.17 points in verbal IQ.

• • 1.03 points in nonverbal IQ.

• The effect of vitamin D status during pregnancy on IQ of the offspring at ages 4-6 was the same for both races.

• The effect of maternal vitamin D status on childhood IQ plateaued at around 40ng/mL, which is near the top of what is considered an adequate level of 25-hydroxyvitamin D.

The authors of the study concluded: “Gestational vitamin D concentrations were positively associated with IQ at age 4-6, suggesting that vitamin D plays an important role in programming neurocognitive development. Vitamin D status may be an important modifiable factor that can be optimized through appropriate nutritional recommendations and guidance. Vitamin D deficiency was especially prevalent among Black women in this cohort, suggesting a higher need for screening and nutritional intervention in this vulnerable population.”

The authors went on to say: “Vitamin D supplementation may be indicated for women who have poor dietary intake of vitamin D and/or reduced cutaneous synthesis related to skin pigmentation [Simply put, sunlight can catalyze the synthesis of vitamin D in our skin, but skin pigmentation filters out the sunlight and decreases vitamin D synthesis.]…”

The Importance Of Vitamin D During Pregnancy

Let me put this study in perspective by first discussing the pros and cons of the study. Then I will close with what I think is the most important takeaway from the study.

The Cons Of The Study:

The cons are obvious:

1. This study shows that a 10 ng/mL increase in 25-hydroxyvitamin D during pregnancy is associated with about a 1-point increase in IQ on a 100-point scale? Is that significant? Probably not, especially when you consider all the other dietary and environmental factors that influence intelligence and educational attainment.

2) We don’t know whether this effect of vitamin D status during pregnancy on IQ will persist as the children grow up. It is more likely that socioeconomic and family factors during childhood will play a much larger role in educational attainment.

The Pros Of The Study:

1. This study is superior to most previous studies on this topic because of its size and duration. It is also a well-designed study.

2) The authors pointed out a previous study has reported that for each decrease of one IQ point:

• • Lifetime income for men decreases by 1.93%.

• • Lifetime income for women decreases by 3.23%.

3) The effect of vitamin D status during pregnancy on IQ at age 4-6 plateaued at 40 ng/mL. That means the women in this study would obtain optimal benefit by increasing their 25-hydroxyvitamin D levels by 20 ng/mL. Since each 10 ng/mL increase in 25-hydroxyvitamin D during pregnancy increased IQ by 1.17, this would translate into:

• A 4.5% increase in lifetime earnings for men.

• A 7.6% increase in lifetime earnings for women.

• When you look at it this way, the effect of vitamin D during pregnancy on IQ seems a bit more significant.

The Most Important Takeaway From This Study:

• Of all the things you can do during pregnancy to give your kids an advantage in today’s competitive world, supplementation with vitamin D before and during pregnancy is probably the simplest, cheapest, and safest option available to you.

• Even if optimizing 25-hydroxyvitamin D levels during pregnancy has no long-term effect on your child’s IQ, we know it has many other benefits for your health and your child’s health.

• And, as long as you don’t exceed 50 ng/mL of 25-hydroxyvitamin D, it is perfectly safe.

The authors had this to say about supplementation with vitamin D before and during pregnancy: “Popular prenatal supplements, which typically contain 400-600 IU vitamin D, are likely insufficient to correct 25-hydroxyvitamin D deficiencies. Randomized controlled trials have suggested that daily supplementation of 800 to 1,000 may be needed during pregnancy, and that doses of 4,000 IU may be ideal in cases of severe deficiency.”

The Bottom Line

A recent study looked at 25-hydroxyvitamin D status during the second trimester of pregnancy and the IQ of the offspring at ages 4-6. The study found:

• The average blood level of 25-hydroxyvitamin D at week 23 of pregnancy was 21.6 ng/mL.

• • 6% of the women were vitamin D deficient (<20 ng/mL 25-hydroxyvitamin D).

• • After adjusting for other variables known to affect IQ, every 10ng/mL increase in 25-hydroxyvitamin D status during pregnancy resulted in an increase of 1.17 points in overall IQ.

• The effect of maternal vitamin D status on childhood IQ plateaued at around 40ng/mL, which is near the top of what is considered an adequate level of 25-hydroxyvitamin D.

The authors of the study concluded: “Gestational vitamin D concentrations were positively associated with IQ at age 4-6, suggesting that vitamin D plays an important role in programming neurocognitive development. Vitamin D status may be an important modifiable factor that can be optimized through appropriate nutritional recommendations and guidance…”

The authors went on to say: “Vitamin D supplementation may be indicated for women who have poor dietary intake of vitamin D and/or reduced cutaneous synthesis related to skin pigmentation…”

In terms of supplementation, the authors said: “Popular prenatal supplements, which typically contain 400-600 IU vitamin D, are likely insufficient to correct 25-hydroxyvitamin D deficiencies. Randomized controlled trials have suggested that daily supplementation of 800 to 1,000 may be needed during pregnancy, and that doses of 4,000 IU may be ideal in cases of severe deficiency.”

For more details and my perspective of the study, read the article above.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease.