Iodine Global Network (IGN)

In the development of verbal IQ in utero, timing matters for healthy iodine nutrition

July, 2019
by Elizabeth Pearce

In the first trimester, and at least three months prior to conception, pregnant women should consume 150 µg of iodine a day.

Pregnant women with healthy iodine nutrition during the first trimester give birth to newborns with higher verbal IQs. In a recent study of 6,180 mother-and-child pairs from the Netherlands, Spain, and the UK, healthy levels of iodine, a critical nutrient for growth and development, were associated with higher child verbal IQs.

This has serious implications for countries, like the U.S., where although the population as a whole is getting adequate iodine nutrition, mild iodine deficiency may be widespread in pregnancy.

So, how do we make sure women get adequate iodine nutrition and ensure the health and vitality of their newborns?

Iodine supports the thyroid, which plays a critical role in growth and development, and thus is essential for a healthy fetus. During pregnancy, iodine is essential for the production of maternal and fetal thyroid hormones. The maternal thyroid hormone crosses the placenta to the fetus early in the first trimester, before the fetal thyroid is functioning. Through its contribution to thyroid hormone production, iodine supports growing fetal bones, tissue, and brain cells.

While it’s already been established that severe maternal iodine deficiency can lead to lower offspring IQ, this study revealed that even mild to moderate nutritional deficiency in iodine can impact neurodevelopment in utero. And, significantly, iodine intake is critical through the first 14 weeks of pregnancy. For a developing fetus, timing matters. Not only is it critically important in the first trimester, but in the family planning stages – ideally women need adequate iodine intake at least three months before becoming pregnant.

Compounding the challenges is that the U.S. is missing an opportunity to protect future generations through the foods we already eat. Unlike nearly two-thirds of the countries in the world, the U.S. does not mandate fortification of salt with iodine. Globally, many pregnant women now consume healthy amounts of iodine through this simple, effective and population scalable intervention: universal salt iodization, or USI.

This is the focus of the Iodine Global Network’s advocacy, and has led to a drastic decline globally in iodine deficiency disorder, which can have debilitating and life-long affects for newborns, including cognitive impairment and stunting.

For pregnant and lactating women in the U.S., the American Thyroid Association recommends supplementing a healthy diet with 150 µg of iodine a day to support healthy growth. This should protect pregnant women and their children from the effects of iodine deficiency, but it is not the ideal long-term solution for the U.S. population, since not all pregnancies are planned, and not all pregnant women are aware of this advice.

At IGN we’ll continue to advocate for the U.S. to mandate iodized salt, even as we urge consumers to choose iodized salt, and dispel some of the myths around non-iodized saltAchtung Link öffnet sich in einem neuen Fenster. In the meantime I’ll be advising my fellow clinicians to recommend that U.S. patients who are planning pregnancy, pregnant, or lactating supplement with iodine for healthier newborns.
This blog was adapted from the following review (source 1) of the original research article (source 2):

1) Mild-to-Moderate Iodine Deficiency in Early Pregnancy Is Associated with Lower Verbal IQ in Children.Achtung Link öffnet sich in einem neuen Fenster Clinical Thyroidology. 2019 May 8.

2) Association of maternal iodine status with child IQ: a meta-analysis of individual-participant data.Achtung Link öffnet sich in einem neuen Fenster J Clin Endocrinol Metab. 2019 Mar 28.

About the author

Dr. Elizabeth Pearce is an endocrinologist at the Boston Medical Center, Professor of Medicine at the Boston University School of Medicine, President of the American Thyroid Association (ATA), and IGN Regional Coordinator for North America. As a clinical investigator and epidemiologist, she has made significant contributions in iodine nutrition, thyroid disease in pregnancy, and environmental thyroid disrupters. She recently co-chaired the ATA’s Thyroid in Pregnancy Guidelines Task Force.