childhood development

Does Vitamin D Affect IQ?

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The Importance Of Vitamin D During Pregnancy

Author: Dr. Stephen Chaney

pregnant women taking vitaminAs 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?

Clinical StudyThis 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?

child geniusHere 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

vitamin dLet 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.

The Effect Of Vitamin D On Childhood Development

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Is Vitamin D Important During Pregnancy?

vitamin dIf you are parents, you want the best for your child. It can be nerve wracking when your child doesn’t meet the expected developmental milestones. When I saw a recent study titled “Association of maternal vitamin D status in pregnancy and neurodevelopmental outcomes in children” ( AL Darling et al, British Journal of Nutrition, 117: 1682-1692, 2017), I knew you would want to hear about it.

But first a bit of background: Based on blood 25-hydroxy vitamin D levels (considered the most accurate marker of vitamin D status):

  • 8-11% of pregnant women in the US are deficient in vitamin D (<30 nmol/L).
  • ~25% of pregnant women have inadequate vitamin D status (30-49 nmol/L).
  • ~65% of pregnant women have adequate vitamin D status (50-125 nmol/L).
  • ~ 1% of pregnant women have high vitamin D levels (>125 nmol/L).

In short, that means around 1/3 of pregnant women in the US have inadequate or deficient levels of vitamin D. The affect of inadequate vitamin D during pregnancy is not just an academic question.

It is a concern because inadequate vitamin D levels during pregnancy has been associated with gestational diabetes (diabetes during pregnancy), low birthweight babies, and a condition called pre-eclampsia (pre-eclampsia is characterized by the development of high blood pressure during pregnancy and can lead to serious, even fatal, complications for mother and baby).

The Cochrane Collaboration (considered the gold standard for evidence-based medicine) has recently reviewed the literature and has reported) that vitamin D during pregnancy “probably reduces the risk of pre-eclampsia, gestational diabetes, and the risk of having a low birthweight baby compared to placebo or no intervention.”

In short, this means the evidence is pretty good that inadequate vitamin D increases the risk of significant complications during pregnancy and that supplementation with vitamin D reduces the risk of those complications.

However, what about the effect of inadequate vitamin D during pregnancy on the development of the newborn child? Here the evidence is less clear. This study was designed to answer that question.

How Was The Study Designed?

clinical studyThis study followed neurodevelopmental milestones of 7065 children born to mothers in the Avon region of southwest England between April 1, 1991 and December 31, 1992. Maternal 25-hydroxy vitamin D levels were measured during pregnancy. The distribution of 25-hydroxy vitamin D levels in this population was very similar to that observed for pregnant mothers in the United States.

The children were followed from 6 months to 9 years of age and the following neurodevelopmental milestones were measured:

  • Gross-motor skills, fine-motor skills, social development, and communication skills were measured at 6, 18, 30, and 42 months.
  • Behavioral development (socialization, hyperactivity, emotional development, and conduct) was measured at 7 years.
  • IQ was measured at 8 years.
  • Reading skill (words/minute, accuracy, and comprehension) was measured at 9 years.

What Is The Effect Of Vitamin D On Childhood Development?

Child raising handThe study compared children of women who had inadequate vitamin D status (<50 nmol/L) during pregnancy to children of women who had adequate vitamin D status (≥50 nmol/L) during pregnancy. Here is what the study found:

The children of mothers with inadequate vitamin D during pregnancy had:

  • Delayed gross-motor skills at 18 and 30 months.
  • Delayed fine-motor skills at 30 and 42 months.
  • Delayed social development at 42 months.

However, when they looked at later years, there was no significant effect of maternal vitamin D status on:

  • Behavioral development at 7 years.
  • IQ at 8 years.
  • Reading skills at 9 years.

This is encouraging because it suggests that the effect of inadequate vitamin D during pregnancy does not have a permanent effect on childhood development. By the time they are 7 or older their nutrition and intellectual stimulation during childhood appears to outweigh the effect of their mother’s nutrition on their development.

In interpreting this information, we need to keep in mind that this study was performed in England, not in a third world country. In particular:

  • England, like the United States, has supplemental food programs for disadvantaged children.
  • England has an excellent educational system. So, we can assume these children also received intellectual stimulation as soon as they reached school age.

Is Vitamin D Important During Pregnancy?

pregnant women taking vitaminIf we focus on a healthy pregnancy, there is good evidence that inadequate vitamin D during pregnancy increases the risk of serious complications and that supplementation with vitamin D can reduce these complications. We also know that vitamin D deficiency during pregnancy can affect bone development in the newborn.

Thus, adequate vitamin D is clearly needed for a healthy pregnancy.

However, if we just consider the effect of maternal vitamin D on childhood development, it would be tempting to downplay the importance of vitamin D during pregnancy. This study focused on vitamin D, but studies focusing on other nutritional deficiencies usually give similar results.

In most of these studies, the effects of inadequate nutrition during pregnancy on childhood developmental milestones appear to be transient. Developmental delays are seen during the first few years of life but disappear as the children get older.

This is incredibly good news. It means that mild nutritional deficiencies during pregnancy do not have to handicap a child for life. If the children are given adequate nutrition and intellectual stimulation as they grow, the poor start they received in life can be erased.

It is also a caution. We already know that poor nutrition during childhood can affect a child’s behavior and intellectual development. If that child also received poor nutrition in the womb, their chances of normal childhood development may be doubly impacted.

In short, if adequate vitamin D during pregnancy improves early developmental milestones in children, that can be viewed as an added benefit.

The only question is how much vitamin D is needed. Fortunately, the present study cast some light on that question.

The study asked whether blood levels of 25-hydroxy vitamin D ≥75 nmol/L were more beneficial than blood levels ≥50 nmol/L. The answer was a clear no. That means an adequate vitamin D status during pregnancy is sufficient to support normal developmental milestones in children.

The current recommendation (DV) of vitamin D3 for pregnant women is 15 mcg (600 IU). Thus, my recommendations are:

  • If you are pregnant, be sure that your prenatal supplement provides at least 600 IU of vitamin D3.
  • If you are a woman of childbearing age, be sure that your multivitamin provides at least 600 IU of vitamin D3.
  • Slightly more is OK but avoid mega doses unless prescribed by a health professional who is monitoring your 25-hydroxy vitamin D status.
  • Because we all utilize vitamin D with different efficiencies, I would recommend asking for a 25-hydroxy vitamin D test and working with your health professional to keep your levels in the adequate range.

The Bottom Line

A recent study looked at the effect of mild vitamin D deficiency during pregnancy on childhood developmental milestones. The study found that children born to vitamin D-deficient mothers had:

  • Delayed gross-motor skills at 18 and 30 months.
  • Delayed fine-motor skills at 30 and 42 months.
  • Delayed social development at 42 months.

This is concerning. However, when they looked at later years, there was no significant effect of maternal vitamin D status on:

  • Behavioral development at 7 years.
  • IQ at 8 years.
  • Reading skills at 9 years.

The is encouraging. The reasons for this are discussed in the article above.

If we summarize this and previous studies, the bottom line is:

  • Adequate vitamin D is clearly needed for a healthy pregnancy.
  • If adequate vitamin D during pregnancy improves early developmental milestones in children, that can be viewed as an added benefit.

For more details and my recommendations on how much vitamin D you need, 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.

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