(P24-074-23) Dietary Iodine Intake Is Decreasing in the US Population: A Time-Trend Analysis of National Health and Nutrition Examination Surveys (NHANES) From 2001–2018

Objectives: Dietary iodine, required for the synthesis of thyroid hormones, is essential for regulating metabolism and brain function. Mild to moderate iodine deficiency is common, placing pregnant/lactating women and their offspring at risk. This study examines trends in dietary iodine intake from 2001-2018 in the US population.

Methods: In this cross-sectional study, dietary intake data from the National Health and Nutrition Examination Survey (NHANES) 2001˗2018 (n=42,524, ages 14+ years) were used to estimate mean (± SE) intake of dietary iodine from food (using the US Department of Agriculture/Food & Drug Administration/Office of Dietary Supplements-National Institutes of Health database) and supplements for each 2-year collection cycle. Means were calculated and time-trends estimated with regression analysis.

Results: There was a significant linear decline in overall population mean intake (-23%) from 238±4 in 2001-2002 to 188±3 µg/day in 2017-2018 (p < 0.0001). Females declined (-21%) from 206±3 to 167±4 (p < 0.0001); males declined (-24%) from 271±7 to 212±4 µg/day (p < 0.0001). In adult females of childbearing age (20–40) years, there were significant decreases in mean iodine intake (-21%) from 216±6 in 2001-2002 to 173±7 µg/day in 2017-2018 (p < 0.0001). The iodine intake of pregnant females (13–54 years) from dietary sources alone (without supplementation) in 2001-2002 was 272±6 but declined by 30% to 200±16 µg/day by 2017-2018. Supplementary sources of iodine improved their status with their total intake equal to 243±12 µg/day in 2017–2018.

Conclusions: There were significant decreases in iodine intake from 2001–2018 in the US population. Many individuals, including women of childbearing age, are probably consuming iodine below recommended levels. Decreasing iodine intake may be due to changes in the food supply and consumption, such as a reduction in intake of iodized-salt, bread and dairy, and changes in food processing. Regulatory and educational strategies to prevent iodine deficiency in vulnerable groups are necessary, given trends in iodine consumption. It is likely these downward trends will persist as changes in the food supply and patterns of food consumption continue to occur.

Funding Sources: Supported by USAMRDC; views expressed are not official US Army, DoD or government policy.