The prevalence of using iodine-containing supplements is low among reproductive-age women, NHANES 1999-2006

Abstract

During pregnancy, the iodine requirement rises to meet demands for neurological development and fetal growth. If these requirements are not met, irreversible pathological cognitive and behavioral changes to the fetus may ensue. This study estimated the prevalence of iodine-containing dietary supplement (DS) use and intakes of iodine from DSs among pregnant women and nonpregnant women of reproductive age (15-39 y) who were interviewed and examined in NHANES 1999-2006 (n = 6404). Although 77.5% of pregnant women reported taking one or more DSs in the past 30 d, only 22.3% consumed an iodine-containing supplement. Most pregnant women reported using one DS and reported taking this product daily. The vast majority of iodine-containing DSs reported by pregnant women claimed an iodine content of 150 μg iodine/serving on the label. Pregnant women using at least one DS containing iodine had a mean daily iodine intake of 122 μg/d from supplements; the median value was 144 μg/d. Median urinary iodine concentrations (UICs) were similar for pregnant and nonpregnant women in the population aged 15-39 y. The median UIC was 148 μg/L for pregnant women and 133 μg/L for nonpregnant women. The WHO has established a cutoff for insufficient iodine intake at <150 μg/L for pregnant women and <100 mg/L for those who are not pregnant. This suggests that as a population, we may not be meeting adequate intakes of iodine for pregnant women. More research is needed on the iodine intakes of pregnant women and women of reproductive age on their total iodine intake from all sources, not just DSs.

FIGURE 1

Flow chart of women in analysis NHANES 1999–2006, ages 15–39 y. *Missing DS data and exclusions (n = 91): Missing both the frequency of use in the past 30 d and how much was taken on days used (n = 52), missing frequency of use in the past 30 d (n = 32), missing how much was taken on days used (n = 6), missing data because the DS product label was missing serving size and amount of iodine (n = 1). ** Missing data and exclusions (n = 94): Missing UIC (n = 49), excluded because of thyroid problem or use of thyroid medication (n = 36), missing DS data (n = 9). DS, dietary supplement; MEC, Mobile Examination Centers; UIC, urinary iodine concentration.