Iodine Intake From Diet and Supplements and Urinary Iodine Concentration in a Cohort of Pregnant Women in the United States

Abstract

BackgroundThe DRI Estimated Average Requirement (EAR) in pregnancy for Iodine (I), an essential nutrient for fetal neurodevelopment, is 160 μg/d. Supplementation with 150 μg/d I/day is recommended during pregnancy, however, neither dietary intake or the combination of diet and supplement intake has been reported in US pregnant women. ObjectiveDetermine iodine intake from diet and supplements and iodine status in pregnancy by urinary iodine concentration in a large cohort of pregnant women. DesignPregnant women (n=750) completed the Diet History Questionnaire 2.0 from the National Institute of Cancer or multiple 24-hour recalls at baseline and identified their prenatal supplement(s). Dietary iodine intake was estimated using the USDA, FDA and ODS-NIH Database for the Iodine Content of Common Foods at enrollment, supplemental iodine intake throughout the study using content databases, and urinary iodine concentration (UIC) by the modified Sandell-Kolthoff reaction in samples collected between 14-20 weeks gestation (n=966). ResultsThe median intake of iodine from diet was 108.8 μg/d, and 63% (473/750) were below the Estimated Average Requirement (EAR). Furthermore, 65% (529/818) took a supplement containing iodine, however, only 32% (259/818) took ≥150 μg/d. Median intake increased to 188.5 μg/d with the inclusion of I from supplements, however , 41% (380/925) remained below the EAR even after supplementation suggesting inadequate intake in nearly half of the cohort. A similar 48% (467/966) had UIC ≤150 μg/L. ConclusionsAssessment of iodine status by UIC and intake of iodine from diet and supplements support a high prevalence of iodine insufficiency during pregnancy in this large cohort of US women.