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Iodine and Cognitive Development

Research Summary and Key Findings on Iodine and Cognitive Development

What Foods Support A Healthy Pregnancy?

Megan Holdaway, RDN, discusses good nutrition during pregnancy and while breastfeeding.

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Iodine as Essential Nutrient during the first 1000 Days of Life 

Iodine is an essential nutrient, particularly crucial for neurodevelopment. Iodine deficiency during pregnancy and maternal hypothyroxinemia can negatively impact brain development and neuro-behavioral performance postnatally.

Source: Velasco et al. Nutrients, 2018. https://www.mdpi.com/2072-6643/10/3/290/htm 

Key findings

Cow Milk Consumption Increases Iodine Status in Women of Childbearing Age in Randomized Controlled Trial 

A randomized controlled trial found that the consumption of additional cow’s milk can significantly increase urinary iodine concentration in women of childbearing age. These results suggest that cow’s milk is a potentially important dietary source of iodine in this population group. Cow milk contributes the greatest amount to iodine intakes in several countries.

Source: O’Kane et al. J Nutr, 2018. https://doi.org/10.1093/jn/nxx043  
Key findings

The Lancet 

Study analyzed mother–child pairs from the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort by measuring urinary iodine concentration (and creatinine to correct for urine volume) in stored samples from 1040 first-trimester pregnant women. After adjustment for confounders, children of women with an iodine-to-creatinine ratio of less than 150 μg/g were more likely to have scores in the lowest quartile for verbal IQ, reading accuracy, and reading comprehension than were those of mothers with ratios of 150 μg/g or more. Our results show the importance of adequate iodine status during early gestation and emphasize the risk that iodine deficiency can pose to the developing infant, even in a country classified as only mildly iodine deficient. Iodine deficiency in pregnant women in the UK should be treated as an important public health issue that needs attention.

Source: Bath SC et al. Lancet, 2013. https://doi.org/10.1016/S0140-6736(13)60436-5  
Key findings

Mild Iodine Deficiency During Pregnancy is Associated with Reduced Educational Outcomes in the Offspring: 9-Year Follow-Up of the Gestational Iodine Cohort 

A longitudinal follow-up (at 9 years old) of the Gestational Iodine Cohort found that children whose mothers had UIC <150 μg/L had reductions of 10.0% in spelling, 7.6% in grammar, and 5.7% in English-literacy performance compared with children whose mothers' UICs were ≥150 μg/L. These associations remained significant after adjustment for a range of biological factors. Differences in spelling remained significant after further adjustment for socioeconomic factors.

Source: Hynes KL et al. J Clin Endocrinol Metab, 2013. https://doi.org/10.1210/jc.2012-4249  
Key findings

Key Findings From Provided Resources

Iodine intake amongst women of childbearing age in the UK 

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4340577/ 
Key findings

Some subgroups of reproductive age women in the United States may be at risk for iodine deficiency  

Source: https://www.ncbi.nlm.nih.gov/pubmed/20554903 
Key findings

Mild to moderate iodine deficiency affect thyroid function in pregnancy

Source: https://www.ncbi.nlm.nih.gov/pubmed/30132420 
Key findings: 

Overview of the disorders caused by iodine deficiency. It emphasizes the role of iodine deficiency in the development of brain damage and neurocognitive impairment

Source: https://www.ncbi.nlm.nih.gov/books/NBK285556/ 
Key findings:

Disorders of the Thyroid Gland in Infancy, Childhood and Adolescence

Source: https://www.ncbi.nlm.nih.gov/books/NBK279032/ 
Key findings: n/a 


Iodine facts for health professionals, from the National Institutes of Health

Source: https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional/ 
Key findings

Table 1: Recommended Dietary Allowances (RDAs) for Iodine [2]

Birth to 6 months110 mcg*110 mcg*  
7–12 months130 mcg*130 mcg*  
1–3 years90 mcg90 mcg  
4–8 years90 mcg90 mcg  
9–13 years120 mcg120 mcg  
14–18 years150 mcg150 mcg220 mcg220 mcg
19+ years150 mcg150 mcg220 mcg220 mcg

* Adequate Intake (AI)  

The World Health Organization (WHO), United Nations Children’s Fund (UNICEF), and the International Council for the Control of Iodine Deficiency Disorders (ICCIDD) recommend a slightly higher iodine intake for pregnant women of 250 mcg per day [3,7]. 

Table 2: Selected Food Sources of Iodine [10,11,12] 

FoodApprox. Micrograms (mcg) per servingPercent DV*
Seaweed, whole or sheet, 1 g16 to 2,98411% to 1,989%
Cod, baked, 3 ounces9966%
Yogurt, plain, low-fat, 1 cup7550%
Iodized salt, 1.5 g (approx 1/4 tsp.)7147%
Milk, reduced fat, 1 cup5637%
Fish sticks, 3 ounces5436%
Bread, white, enriched, 2 slices4530%
Fruit cocktail in heavy syrup, 1/2 cup4228%
Shrimp, 3 ounces3523%
Ice cream, chocolate, 1/2 cup3020%
Macaroni, enriched, boiled, 1 cup2718%
Egg, 1 large2416%
Tuna, canned in oil, drained, 3 ounces1711%
Corn, cream style, canned, 1/2 cup149%
Prunes, dried, 5 prunes139%
Cheese, cheddar, 1 ounce128%
Raisin bran cereal, 1 cup117%
Lima beans, mature, boiled, 1/2 cup85%
Apple juice, 1 cup75%
Green peas, frozen, boiled, 1/2 cup32%
Banana, 1 medium32%

*DV = Daily Value. The U.S. Food and Drug Administration (FDA) developed DVs to help consumers compare the nutrient contents of products within the context of a total diet. The DV for iodine is 150 mcg for adults and children age 4 years and older [13]. FDA does not require food labels to list iodine content unless a food has been fortified with this nutrient. Foods providing 20% or more of the DV are considered to be high sources of a nutrient, but foods providing lower percentages of the DV also contribute to a healthful diet. 

The U.S. Department of Agriculture’s (USDA’s) National Nutrient Database [14] does not list the iodine content of foods or provide lists of foods containing iodine. 

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