A Modified Iodine Balance Study to Explore the Recommended Nutrient Intake of Iodine in Chinese Preschool Children Aged 3 to 6 Years

The recommended nutrient intakes (RNI) for iodine in preschool children in China are outdated. The study aimed to establish optimal iodine intake for Chinese preschool children aged 3-6 years using a modified iodine balance methodology. During the 3-day iodine balance study, 75 healthy preschool children aged 3-6 years were randomly divided into three groups. Dietary interventions were applied to bal-ance the proportion of children with positive and negative iodine balance across groups. All food items consumed and excreta (urine, feces) were systematically col-lected to analyze the relationships among daily iodine intake, excretion, and retention. A total of 42 children (56.0%) were in negative iodine balance, while 33 children (44.0%) were in positive iodine balance. The zero iodine balance value (defined as the iodine intake level at which intake equals excretion) among the three groups increased with higher iodine intake. A significant positive association was observed between iodine intake and iodine excretion (β: 0.45; 95% CI: 0.30, 0.60; P < 0.001), with an obligatory iodine excretion of 36 μg/d. Additionally, iodine intake was significantly associ-ated with increased iodine retention (β: 0.55; 95% CI: 0.40, 0.70; P < 0.001). The zero io-dine balance value for preschool children aged 3-6 years was determined to be 65.6 μg/d. Our study estimated the estimated average requirement (EAR) for iodine in preschool children aged 3-6 years in China to be 65.6 μg/d, and the calculated RNI is 90 μg/d. Our study provides critical data support for establishing China's dietary reference intakes for iodine.