Re-exploration of dietary iodine intake in Chinese adult males using a modified iodine balance study.

There is still controversy about optimal dietary iodine intake as the Universal Salt Iodization (USI) policy enforcement in China. A modified iodine balance study was thus conducted to explore the suitable iodine intake in Chinese adult males using the iodine overflow hypothesis. In this study, 38 apparently healthy males (19.1±0.6 years) were recruited and provided with designed diets. After the 14-days iodine depletion, daily iodine intake gradually increased in the 30-days iodine supplementation, consisting of 6 stages and each of 5-days. All foods and excreta (urine, faeces) were collected to examine daily iodine intake, iodine excretion and the changes of iodine increment in relation to those values at stage 1. The dose-response associations of iodine intake increment with excretion increment were fitted by the mixed effects models (MEMs), as well as with retention increment. Daily iodine intake and excretion were 16.3 and 54.3 μg/day at stage 1, and iodine intake increment increased from 11.2 μg/day at stage 2 to 118.0 μg/day at stage 6, whilst excretion increment elevated from 21.5 to 95.0 μg/day. A zero iodine balance was dynamically achieved as 48.0 μg/day of iodine intake. The estimated average requirement (EAR) and recommended nutrient intake (RNI) were severally 48.0 and 67.2 μg/day, which could be corresponded to a daily iodine intake of 0.74 and 1.04 μg/kg/day. The results of our study indicate that roughly half of current iodine intakes recommendation could be enough in Chinese adult males, which would be beneficial for the revision of dietary reference intakes (DRIs).