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Pregnant Women Need Iodine for Baby’s Brain, Why and How Much?

Pregnant and iodine deficiency

If you are pregnant or plan to get pregnant, be sure to get a sufficient amount of iodine in your diet. Results of two new studies show that an iodine deficiency during pregnancy can have a negative impact on a baby’s brain. Why can this occur, and how much iodine do pregnant women need?

How iodine deficiency affects a child’s brain

Iodine is a nutrient trace mineral present naturally in the body. The main functions of iodine are metabolism of food into energy and healthy operation of the thyroid gland, which involves the secretion of hormones that are necessary for brain development.

In one of the two new studies, a research team from Bristol and Surrey universities evaluated data from the Avon Longitudinal Study of Parents and Children (ALSPAC), which involved more than 14,000 women who were pregnant in 1991 and 1992. The children of these women have been followed since that time.

Iodine concentrations were obtained during the first trimester of 1,040 pregnant women and the women were categorized as being iodine deficient (less than 150 mcg/g, or 150 micrograms per gram) or iodine sufficient (150 mcg/g or higher). Sixty-seven percent of the women were identified as being iodine deficient.

When the offspring of all the women were evaluated at ages 8 and 9 years, after adjusting for factors such as breastfeeding and parents’ education, here were the findings:

  • Children whose mothers were iodine deficient were much more likely to score low on verbal IQ, reading comprehension, and reading accuracy than those whose mothers had sufficient iodine
  • The lower a mother’s iodine concentration, the lower the children’s average IQ and reading ability

Second study on iodine and pregnancy
In a second study on iodine and pregnancy, which was conducted in Australia, researchers analyzed the test scores of 228 children aged 9 years who had been born to mothers who had been iodine deficient during pregnancy. The youngsters’ diets had been supplemented with iodine during childhood.

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Investigators found that “children may continue to experience the effects of insufficient iodine for years after birth,” according to Kristen L. Hynes, PhD, the study’s lead author, of Menzies Research Institute at the University of Tasmania. It appeared that iodine supplementation during childhood was not sufficient to reverse the effects of iodine deficiency in the womb.

Those effects included the following:

  • Lower scores on standardized literary tests, especially in spelling
  • No association was observed between inadequate iodine exposure and math scores, however

What women need to know
The Food and Nutrition Board at the Institute of Medicine recommends all females and males age 14 years and older get 150 mcg of iodine daily to maintain health. Although iodized salt is a major source of iodine in the diets of many women, those who are on low-salt diets may experience low iodine levels.

Food sources of iodine include fish (saltwater fish have about six times more iodine than freshwater fish), eggs (1.6 mcg/g), and yogurt (0.7 mcg/g). One-quarter teaspoon of iodized salt contains about 95 mcg, while 3 ounces of saltwater fish may contain about 325 mcg.

Women who plan to get pregnant or who are pregnant should discuss the possibility of iodine deficiency with their healthcare provider. Iodine deficiency is preventable, and addressing the issue during pregnancy can protect a baby’s brain and future development.

Bath SC et al. Effect of inadequate iodine status in UK pregnant women on cognitive outcomes in their children: results from the Avon Longitudinal Study of Parents and Children (ALSPAC). The Lancet 2013 May 22. DOI:10.1016/S0140-6736(13)60536-5
Hynes KL et al. Mild iodine deficiency during pregnancy is associated with reduced educational outcomes in the offspring: 9-year follow-up of the Gestational Iodine Cohort. Journal of Clinical Endocrinology & Metabolism 2013; 98: 1954-62

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