Iodine inadequacy is prevalent and has continuously increased from 2001 to 2018 in the U.S.

Background: There have been continuous changes in the production and processing of major sources of iodine in the diet, especially iodized salt, dairy, and bread, that have reduced iodine intake in the United States.

Objective: To assess iodine status and trends over 18 years in US adults and adolescents, with emphasis on vulnerable groups, including women of reproductive age (WRA), pregnant women, and specific ethnic groups.

Methods: Creatinine corrected urinary iodine excretion (UI/Cr), a standard method for evaluating population iodine status, was assessed using National Health and Nutrition Examination Survey (NHANES) data collected in 2001-2018 of individuals 14+ years (N=22,851). Median values and % < Estimated Average Requirement (EAR) from 2001-2002 were compared to 2017-2018 values. Trends from 2001-2018 were examined with linear regression. Inadequate iodine status was estimated by determining population proportions below EAR.

Results: In 2017-2018, 35% of WRA and 46% of pregnant women had inadequate intakes. For the same time period, 2017-2018, 44% of Non-Hispanic Black, 32% Mexican American, and 25% Other Hispanic women ≥14 years had inadequate intakes. Twenty-four percent of females aged ≥14 years had inadequate intakes in 2017-2018 versus 12% in 2001-2002 (p<0.001). Thirty percent of males aged ≥14 years had inadequate intakes in 2017-2018 versus 17% in 2001-2002 (p<0.001). Time trend analysis found linear decreases (p<0.05) in median UI/Cr levels for females and males ≥14 years and ≥19 years.

Conclusions: In the total US population over 14+ years prevalence of individuals