The Perils Of Iodine Deficiency For Women

Where Can You Get The Iodine You Need?

Author: Dr. Stephen Chaney

SaltIt shouldn’t be happening. The introduction of iodized salt in the 1920s virtually eliminated iodine deficiency in this country. However, in just the past twenty years the incidence of iodine deficiency has increased 3-8-fold in women of childbearing age. Recent studies have estimated that today 30-40% of women of childbearing age are iodine deficient.

How did that happen?

  • We have been told to cut back on sodium. Many Americans have responded by throwing away the (iodized) salt shaker. Unfortunately, we still get a lot of salt from processed foods, and that salt is usually non-iodized.
  • When we do add salt to our foods it is usually the “healthier” designer salts. First it was sea salt. Now it is trendy versions like Pink Himalayan Salt. While sea salt might have some iodine naturally, the trendier versions are non-iodized.

The consequences of iodine deficiency, especially among women of childbearing age, are alarming. In a previous issue of “Health Tips From the Professor” I reported that iodine is essential for bone and neural development during fetal development and infancy.

This study (JL Mills et al, Human Reproduction, doi: 10.1093/humrep/dex379, 2018) reports that iodine deficiency also reduces a woman’s chances of becoming pregnant.

How Was The Study Done?

Clinical StudyThis study recruited 501 couples (ages 18-40) from 16 counties in Michigan and Texas. The women had all discontinued conception within the previous two months with the intention of becoming pregnant and were followed for an additional 12 months. Women with known thyroid disease were excluded from the study.

Urine samples were collected from each woman at the beginning of the study to determine iodine and creatine levels. The women used fertility monitors to time intercourse relative to ovulation (Basically, that means they optimized their chances of becoming pregnant). They then used digital home pregnancy monitors on the day of expected menstruation to identify pregnancies.

Finally, 90% of the women took either a multivitamin or a prenatal vitamin during the study (The significance of this will be discussed later).

The Perils Of Iodine Deficiency For Women

healthy pregnancyThe results of the study were:

  • 44.3% of the women in the study were iodine deficient (defined as iodine-creatine ratios of <100 mcg/g). This was further broken down to:
    • 21.8% were mildly iodine deficient (50-99 mcg/g).
    • 20.8% were moderately iodine deficient (20-49 mcg/g).
    • 1.7% were severely iodine deficient (<20 mcg/g).
  • That is a total of 22.5% who had moderate to severe iodine deficiency.
  • Women who had moderate to severe iodine deficiency had a 46% decrease in the chance of becoming pregnant over each menstrual cycle compared to the iodine sufficient group.

A simple way of reporting those data would be to say that their chances of becoming pregnant were reduced by 46%, but that would not convey the whole picture. Most of the women did become pregnant during the 12-month study. However, it took the women with moderate to severe iodine deficiency twice as long to become pregnant. Iodine deficiency did not prevent pregnancy from occurring, but it delayed it.

The authors concluded: “In summary, our data show that groups of women with iodine concentrations in the moderate to severe deficient range experience a significantly longer time to pregnancy…The US and European countries where iodine deficiency is common should evaluate the need for programs to increase iodine intake for women of childbearing age, particularly those trying to become pregnant.”

And the increased difficulty in becoming pregnant is just the tip of the iceberg. As I mentioned above, the consequences of iodine deficiency among women of childbearing age, can be devastating.

Iodine is essential for bone and neural development during fetal development and infancy. The American Academy of Pediatrics, The National Institutes Of Health, and the World Health Organization have all declared that mild iodine deficiency during pregnancy can prevent normal cognitive development and reduce IQ levels in children.

Because the consequences of iodine deficiency during pregnancy are so detrimental, if iodine deficiency also reduced the chances of a woman becoming pregnant, it could be considered a good thing. It could be part of Nature’s Plan. Unfortunately, this study suggests that iodine deficiency only delays pregnancy. It doesn’t prevent it.

Where Can You Get The Iodine You Need?

SeaweedSince iodine is so essential for a healthy pregnancy, the important question becomes: “Where can you get the iodine you need?”

  • You could start by using old-fashioned iodized salt rather than designer salts in your salt shaker. However, I am reluctant to recommend anything that would increase sodium intake. We get far too much from processed foods already.
  • Seafood (or seaweed, if you are a vegetarian) are the best food sources of iodine. However, our oceans are so contaminated I would recommend consuming those foods only occasionally.
  • You will often see bread and dairy mentioned as good food sources because iodine was used in the preparation of those foods. However, iodine has largely been replaced by other agents, so those foods should no longer be considered good sources. For example:
    • Iodine in commercial breads has traditionally come from the use of iodate as a dough conditioner. Today iodate has largely been replaced with bromide in commercial bread making. Not only does this trend decrease the amount of iodine available in our diet, but bromide also interferes with iodine utilization in our bodies
    • Iodine in milk has traditionally come from the use of iodine-containing disinfectants to clean milk cans and teats. However, they have largely been replaced with other disinfectants
  • Fruits and vegetables are a variable source of iodine, depending on where they were grown. That is because iodine levels in the soils vary tremendously from region to region.
  • That leaves multivitamins and prenatal vitamins as your best source. However, you do need to read labels. You should look for supplements that provide 150 mcg of iodine. Unfortunately, only 50% of prenatal supplements in the United States even contain iodine. Remember, 90% of the women in this study took either a multivitamin or prenatal supplement and 44.3% of them were iodine deficient.

The Bottom Line

The introduction of iodized salt in the 1920s virtually eliminated iodine deficiency in this country. Now, almost 100 years later, iodine deficiency is back. Recent studies estimate that 30-40% of women of childbearing age are iodine deficient. This is concerning. Previous studies have shown iodine deficiency affects mental development during fetal development and infancy. A recent study suggests that iodine deficiency may also make it more difficult for women to become pregnant. Specifically, the study reported:

  • 44.3% of the women in the study were iodine deficient. This was further broken down to:
    • 21.8% were mildly iodine deficient.
    • 20.8% were moderately iodine deficient.
    • 1.7% were severely iodine deficient.
  • That is a total of 22.5% with moderate to severe iodine deficiency.
  • Women who had moderate to severe iodine deficiency had a 46% decrease in their chance of becoming pregnant over each menstrual cycle compared to the iodine sufficient group.

A simple way of reporting those data would be to say that their chances of becoming pregnant were reduced by 46%, but that would not convey the whole picture. Most of the women did become pregnant during the 12-month study. However, it took the women with moderate to severe iodine deficiency twice as long to become pregnant. Iodine deficiency did not prevent pregnancy from occurring, but it delayed it.

For more details about why iodine deficiency has reemerged in this country and where we can get the iodine we 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.

How Much Omega-3 Should You Take During Pregnancy?

Which Omega-3s Are Beneficial? 

Author: Dr. Stephen Chaney

Premature BabyPreterm births (births occurring before 37 weeks) are increasing in this country. Just between 2018 and 2019, the percentage of preterm births increased by 2% to over 10% of all pregnancies. That is a concern because preterm births are associated with an increased risk of:

  • Visual impairment.
  • Developmental delays.
  • Learning difficulties.
  • Problems with normal development of lungs, eyes, and other organs.

Plus, it is expensive to keep premature babies alive. One recent study estimated that reducing the incidence of preterm births by around 50% could reduce health care costs by $6 billion in the United Stated alone.

Of the 10% preterm births, 2.75% of them are early preterm births (births occurring before 34 weeks). Obviously, the risk of health problems and the cost of keeping them alive is greatest for early preterm babies.

We don’t know why preterm births are increasing, but some experts feel it is because in this country:

  • More older women are having babies.
  • There is increased use of fertility drugs, resulting in multiple babies

Unfortunately, there is no medical standard for identifying pregnancies at risk for preterm birth. Nor is there any agreement around prevention measures for preterm births.

However, recent research has suggested that some premature births may be caused by inadequate omega-3 status in the mother and can be prevented by omega-3 supplementation.

What Do We Know About Omega-3s And Risk Of Preterm Births?

omega-3s during pregnancy is healthyThe role of omega-3s on a healthy pregnancy has been in the news for some time. Claims have been made that omega-3s reduce preterm births, postnatal depression, and improve cognition, IQ, vision, mental focus, language, and behavior in the newborn as they grow.

The problem is that almost all these claims have been called into question by other studies. If you are pregnant or thinking of becoming pregnant, you don’t know what to believe.

Fortunately, a group called the Cochrane Collaboration has recently reviewed these studies. The Cochrane Collaboration consists of 30,000 volunteer scientific experts from across the globe whose sole mission is to analyze the scientific literature and publish reviews of health claims so that health professionals, patients, and policy makers can make evidence-based choices about health interventions. Their reviews are considered the gold standard of evidence-based medicine.

This is because most published meta-analyses simply report “statistically significant” conclusions. However, statistics can be misleading. As Mark Twain said: “There are lies. There are damn lies. And then there are statistics”.

The problem is the authors of most meta-analyses group studies together without considering the quality of studies included in their analysis. This creates a “Garbage In – Garbage Out” effect. If the quality of individual studies is low, the quality of the meta-analysis will also be low.

The Cochrane Collaboration reviews are different. They also report statistically significant conclusions from their meta-analyses. However, they carefully consider the quality of each individual study in their analysis. They look at possible sources of bias. They look at the design and size of the studies. Finally, they ask whether the conclusions are consistent from one study to the next. They clearly define the quality of evidence that backs up each of their conclusions.

For omega-3s and pregnancy, the Cochrane Collaboration performed a meta-analysis and review of 70 randomized controlled trials that compared the effect of added omega-3s on pregnancy outcomes with the effect of either a placebo or no omega-3s. These trials included almost 19,927 pregnant women.

This Cochrane Collaboration Review looked at all the claims for omega-3s and pregnancy outcome, but they concluded that only two of the claims were supported by high-quality evidence:

  • Omega-3s reduce the risk of preterm births.
  • Omega-3s reduce the risk of low birth-weight infants.

The authors concluded: “Omega-3 supplementation during pregnancy is an effective strategy for reducing the riskclinically proven of preterm birth…More studies comparing [the effect of] omega-3s and placebo [on preterm births] are not needed at this point.”

In other words, they are saying this conclusion is definite. The Cochrane Collaboration has declared that omega-3 supplementation should become part of the standard of medical care for pregnant women.

However, the Cochrane Collaboration did say that further studies were needed “…to establish if, and how, outcomes vary by different types of omega-3s, timing [stage of pregnancy], doses [of omega-3s], or by characteristics of women.”

That’s because these variables were not analyzed in this study. The study included clinical trials:

  • Of women at low, moderate, and high risk of poor pregnancy outcomes.
  • With DHA alone, with EPA alone, and with a mixture of both.
  • Omega-3 doses that were low (˂ 500 mg/day), moderate (500-1,000 mg/day), and high (> 1,000 mg/day).

I have discussed these findings in more detail in a previous issue of “Health Tips From The Professor”

How Was This Study Done?

Clinical StudyThe current study (SE Carlson et al, EClinicalMedicine, 2021) is a first step towards answering those questions.

The authors of this study focused on how much DHA supplementation is optimal during pregnancy. This is an important question because there is currently great uncertainty about how much DHA is optimal:

  • The American College of Obstetrics and Gynecology recommends supplementation with 200 mg/day of DHA. However, that recommendation assumes that the increase will come from fish and was influenced by concerns that omega-3-rich fish are highly contaminated with heavy metals and PCBs.
  • Another group of experts was recently asked to develop guidelines for omega-3 supplementation during pregnancy. They recommended pregnant women consume at least 300 mg/day of DHA and 220 mg/day of EPA.
  • The WHO has recommended of minimum dose of 1,000 mg of DHA during pregnancy.
  • Many prenatal supplements now contain 200 mg of DHA, but very few provide more than 200 mg.

Accordingly, the authors took the highest and lowest recommendations for DHA supplementation and asked whether 1,000 mg of DHA per day was more effective than 200 mg of DHA at reducing the risk of early preterm births. Their hypothesis was that 1,000 mg of DHA would be more effective than 200 mg/day at preventing early preterm births.

This study was a multicenter, double-blind, randomized trial of 1032 women recruited at one of three large academic medical centers in the United States (University of Kansa, Ohio State University, and University of Cincinnati).

  • The women were ≥ 18 years old (average age = 30) and between 12 and 20 weeks of gestation when they entered the study.
  • The breakdown by ethnicity was 50% White, 22% Black or African American, 22% Hispanic, 6% Other.
  • 18% had a prior preterm birth (<37 weeks) and 7% had a prior early preterm birth (<34 weeks).
  • Prior to enrollment in the study 47% of the participants reported taking a DHA supplement and 19% of the participants took a DHA supplement with > 200 mg/day.

All the participants received 200 mg DHA capsules and were told to take one capsule daily. The participants were also randomly assigned to take 2 additional capsules that contained a mixture of corn and soybean oil (the 200 mg DHA/day group) or 2 capsules that contained 400 mg of DHA (the 1,000 mg DHA/day group). The capsules were orange flavored so the participants could not distinguish between the DHA capsules and the placebo capsules.

Blood samples were drawn upon entry to the study and either just prior to delivery or the day after delivery to determine maternal DHA status.

The study was designed to look at the effect of DHA dose (1,000 mg or 200 mg) on early preterm birth (<34 weeks), preterm birth (<37 weeks), low birth weight (< 3 pounds), and several other parameters related to maternal and neonatal health.

How Much Omega-3 Should You Take During Pregnancy?

pregnant women taking omega-3The primary findings from this study were:

  • The rate of early preterm births (<34 weeks) was less (1.7%) for pregnant women taking 1,000 mg of DHA/day compared to 200 mg/day (2.4%).
  • The rate of late preterm births (between 34 and 37 weeks) was also less for women taking 1,000 mg of DHA/day compared to 200 mg/day.
  • Finally, low birth weight and the frequency of several maternal and neonatal complications during pregnancy, delivery, and immediately after delivery were also lower with 1,000 mg/day of supplemental DHA than with 200 mg/day.

This confirms the authors’ hypothesis that supplementation with 1,000 mg/day of DHA is more effective than 200 mg/day at reducing the risk of early preterm births. In addition, this study showed that supplementation with 1,000 mg of DHA/day had additional benefits.

This study did not have a control group receiving no DHA. However:

  • The US average for early preterm births is 2.74%.
  • For the women in this study who had previous pregnancies, the rate of early preterm birth was 7%.

Of course, the important question for any study of this type is whether all the women benefited equally from supplementation. Fortunately, this study was designed to answer that question.

As noted above, each woman was asked whether they took any DHA supplements at the time they enrolled in the study, and 47% of the women in the study were taking DHA supplements when they enrolled. In addition, the DHA status of each participant was determined from blood samples taken at the time the women were enrolled in the study. When the authors split the women into groups based on their DHA status at the beginning of the study:

  • For women with low DHA status the rate of early preterm births was 2.0% at 1,000 mg of DHA/day versus 4.1% at 200 mg of DHA/day.
  • For women with high DHA status the rate of early preterm births was around 1% for both 1,000 mg of DHA/day and 200 mg of DHA/day.

In other words, DHA supplementation only appeared to help women with low DHA status. This is good news because:

  • DHA status is an easy to measure predictor of women who are at increased risk of early preterm birth.
  • This study shows that supplementation with 1,000 mg of DHA/day is effective at reducing the risk of early premature birth for women who are DHA deficient.

In the words of the authors, “Clinicians could consider prescribing 1,000 mg DHA daily during pregnancy to reduce early preterm birth in women with low DHA status if they are able to screen for DHA.”

Which Omega-3s Are Beneficial?

DHA is the most frequently recommended omega-3 supplement during pregnancy.

It is not difficult to understand why that is.

  • DHA is a major component of the myelin sheath that coats every neuron in the brain. [You can think of the myelin sheath as analogous to the plastic coating on a copper wire that allows it to transmit electricity from one end of the wire to the other.]
  • Unlike other components of the myelin sheath, the body cannot make DHA. It must be provided by the diet.
  • During the third trimester, DHA accumulates in the human brain faster than any other fatty acid.
  • Animal studies show that DHA deficiency during pregnancy interferes with normal brain and eye development.
  • Some, but not all, human clinical trials show that DHA supplementation during pregnancy improves developmental and cognitive outcomes in the newborn.
  • Recent studies have shown that most women in the United States only get 60-90 mg/day of DHA in their diet.

Clearly, DHA is important for fetal brain development during pregnancy, and most pregnant women are not getting enough DHA in their diet. This is why most experts recommend supplementation with DHA during pregnancy. And this study suggests supplementation with 1,000 mg/day is better than 200 mg/day. However, two important questions remain:Questioning Woman

#1: Is 1,000 mg of DHA/day optimal? The answer is, “We don’t know”. This study compared the highest recommended dose (1,000 mg/day) with the lowest recommended dose (200mg/day) and concluded that 1,000 mg/day was better than 200 mg/day.

But would 500 or 800 mg/day be just as good as 1,000 mg/day? We don’t know. More studies are needed.

#2: Can DHA do it all, or are other omega-3s also important for a healthy pregnancy? As noted above, the emphasis on supplementation with DHA was based on the evidence for a role of DHA in fetal brain development during pregnancy.

But is DHA or EPA more effective at preventing early preterm birth and maternal pregnancy complications? Again, we don’t know.

As noted above, the Cochrane Collaboration concluded that omega-3s were effective at reducing early preterm births but was unable to evaluate the relative effectiveness of EPA and DHA because their review included studies with DHA only, EPA only, and EPA + DHA.

This is an important question because the ability of the body to convert EPA to DHA and vice versa is limited (in the 10-20%) range. This means that if both EPA and DHA are important for a healthy pregnancy, it might not be optimal to supplement with a pure DHA or pure EPA supplement.

Based on currently available data if you are pregnant or thinking of becoming pregnant, my  recommendations are:

  • Chose a supplement that provides both EPA and DHA.
  • Because the evidence is strongest for DHA at this time, chose an algal source of omega-3s that has more DHA than EPA.
  • Aim for a dose of DHA in the 500 mg/day to 1,000 mg/day range. Remember, this study showed 1,000 mg/day was better than 200 mg/day but did not test whether 500 or 800 mg/day might have been just as good.

As more data become available, I will update my recommendations.

The Bottom Line

The Cochrane Collaboration recently released a report saying that the evidence was definitive that omega-3 supplementation during pregnancy reduced the risk of early preterm births. However, they were not able to reach a definitive conclusion on the optimal dose of omega-3s or the relative importance of EPA and DHA at preventing early preterm birth.

Most experts recommend that pregnant women supplement with between 200 mg/day and 1,000 mg/day of DHA.

A recent study asked whether 1,000 mg of DHA/day was better than 200 mg/day at reducing the risk of early preterm birth. The study found:

  • The rate of early preterm births (<34 weeks) was less (1.7%) for pregnant women taking 1,000 mg of DHA/day than pregnant women taking 200 mg/day (2.4%).
  • For women with low DHA status at the beginning of the study, the rate of early preterm births was 2.0% at 1,000 mg of DHA/day versus 4.1% at 200 mg of DHA/day.
  • For women with high DHA status at the beginning of the study, the rate of early preterm births was around 1% for both 1,000 mg of DHA/day and 200 mg of DHA/day.

The authors concluded, “Clinicians could consider prescribing 1,000 mg DHA daily during pregnancy to reduce early preterm birth in women with low DHA status…”

There are two important caveats:

  • This study did not establish the optimal dose of DHA. The study concluded that 1,000 mg/day was better than 200 mg/day. But would 500 or 800 mg/day be just as good as 1,000 mg/day? We don’t know. More studies are needed.
  • This study did not establish the relative importance of EPA and DHA for reducing the risk of early preterm births. DHA is recommended for pregnant women based on its importance for fetal brain development. But is DHA more important than EPA for reducing the risk of early preterm births? Again, we don’t know. More studies are needed.

For more details about this study and my recommendations, 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.

Does Vitamin D Affect IQ?

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

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.

Health Tips From The Professor