Iodine Status of the U.S. Population, National Health and Nutrition Examination Survey, 2005–2006 and 2007–2008
Caldwell, Kathleen L.;
Jones, Robert L.;
Wang, Richard Y.
Background: This report presents urinary iodine (UI) concentrations for the general U.S. population during 2005–2006 and 2007–2008. These findings are the fourth and fifth assessments of the population since National Health and Nutrition Examination Survey (NHANES) III (1988–1994), when the median UI concentration for the population decreased from NHANES I (1971–1974).
Methods: During 2005–2006 and 2007–2008, ∼5000 participants per year were selected to participate in NHANES. The participants were interviewed and examined. UI concentration was measured on a random one third subsample of 2649 participants, aged 6 years and older in 2005–2006, and in all participants in 2007–2008. These urine iodine concentrations are representative of the general U.S. population by age, sex, and race/ethnicity.
Results: (i) The median UI concentrations for the general U.S. population in 2005–2006 and 2007–2008 were 164 μg/L (95% confidence interval [CI] 154–174) and 164 μg/L (95% CI 154–173), respectively. Also, the proportions of the population with a UI concentration of <50 μg/L during these survey periods were 9.8% ± 1.3% and 8.8% ± 0.4%, respectively. The median UI concentration and prevalence of ≥200 μg/L appeared to be higher in children and persons ≥70 years than in other age groups. (ii) In both surveys, children aged 6–11 years had median UI concentrations of ≥200 μg/L, and about 5% of them had a UI concentration of <50 μg/L. (iii) All pregnant women (sample size 184) surveyed during 2005–2008 had a median UI concentration of 125 μg/L (95% CI 86–198), and 56.9% ± 7.9% of this group had a UI concentration of <150 μg/L. UI concentrations were lower among non–Hispanic black survey participants than non–Hispanic white and Mexican-American participants.
Conclusions: These findings affirm the stabilization of UI concentration and adequate iodine nutrition in the general U.S. population since 2000. However, certain groups likely do not achieve a sufficient dietary iodine intake according to the World Health Organization. The needs of these vulnerable groups and the inadequacy of their dietary iodine intake should be addressed in future efforts.