Two-Dose Crossover Iodine Balance Study: Iodine Requirements for Toddlers in China

There is a possibility that the iodine requirement for toddlers currently used in China is underestimated. This study aimed to conduct an iodine balance study in Chinese toddlers. We used a two-dose crossover experimental design, relying on the local iodine concentration in drinking water, and adjusting the iodine intake level by adjusting the toddlers' daily consumption of local drinking water. We measured daily iodine intake, excretion, and retention in toddlers and used linear mixed-effects models were used to fit the relationship between total iodine intake and iodine retention. This study involved 26 toddlers aged 2-3 years. Based on the daily total iodine intake and iodine balance values of the toddlers, a mixed effects model was applied to fit the regression curve, and the regression equation was obtained: y = 0.214x - 16.68, from which the EAR and RNI levels of the toddlers were calculated to be approximately 80 µg/day, and 110 µg/day, respectively. In our study, we expected the reference values for daily iodine EAR and RNI levels in toddlers with their current iodine nutrition status to be about 80 µg/day and 110 µg/day, respectively.