碘是人体必需微量元素，缺乏和过量均会对人体健康产生危害。儿童是碘营养敏感人群，研究显示即使轻微的碘摄入不足也会对儿童生长发育等产生影响，因而亟需明确儿童的碘生理需要量和推荐摄入量标准，指导儿童安全科学补碘。目前关于儿童碘膳食参考摄入量的研究较少，且相关数据过于陈旧。本研究在前期本课题组对高水碘儿童碘安全摄入量上限值研究的基础上，拟通过对高水碘地区、而实际水碘水平较低并未供应碘盐的儿童进行人群流行病学调查，进一步对不同程度碘缺乏暴露儿童的甲状腺功能进行综合评估，明确不同碘摄入不足下儿童甲状腺功能变化情况，以期得到最低的碘安全摄入水平；同时对碘营养适宜的儿童，进行改良后的碘平衡实验，准确评估其摄入量和排出量，得出“零碘平衡”下儿童的平均摄入水平。综合人群水平和个体水平的研究，得出适宜于我国儿童碘膳食推荐摄入量水平的直接数据，指导儿童安全补碘预防碘缺乏，为我国碘膳食参考摄入量标准修订提供数据。

Iodine is one of essential micronutrient for human, both iodine deficiency and excess will be harmful for human health. Children is the susceptible population to iodine nutrition, and studies show that even mild iodine deficiency would affect the growth and development of children, so it is urgent to identify the dietary recommended nutrient intake (RNI) of iodine for children to guide children scientifically and safely supplement iodine. There are few studies about the dietary recommended nutrient intake (RNI) of iodine in children, and present data are old and outdated. Based on the our previous study on upper safe level of iodine on children from areas with high iodine in drinking water, this study will conduct an epidemiological study on children living in areas with high water iodine content but the actual iodine content in their drinking water is not so high, while no supply of iodized salt. We will comprehensively assess thyroid function of children when exposed to different levels of iodine deficiency, to define the changes of thyroid function in children with different iodine intakes and fine the lowest safe iodine intake level at population. Meanwhile, we will conduct revised iodine balance study on children with sufficient iodine nutrition. We will collect the food samples by using duplicate portion method and precisely estimate iodine intake and excretion of children. We will use the regression model to obtain an iodine intake value when children at “zero iodine” balance. Combine the study at population and individual level, we will obtain data on dietary recommended nutrient intake (RNI) of iodine for Chinese children, to properly guide children iodine supplementation to avoid iodine deficiency, which also will provide data for the update of Chinese dietary reference intakes of iodine.