中国居民碘营养健康风险评估

我国碘元素的天然分布极不均匀,因此对地域差异缺乏考虑的全民食盐加碘政策(USI)并非碘缺乏病的最适宜的防控策略,甚至还增加了"碘过量"导致的潜在健康风险。近年来,中国卫生部多次调整食盐加碘政策,但亟需从健康风险评估的角度对该政策进行科学的论证和解读。通过解析全国碘缺乏病监测数据中8～10岁儿童尿碘浓度的数据,采用有阈值的剂量效应曲线,评价了中国居民碘营养健康状况,并计算出全国31个省级地区8～10岁儿童因碘过量导致的"亚临床甲状腺功能减低(亚甲减)"的发病率,最后利用5%基准剂量(benchmark dose,BMD),并结合我国居民膳食营养结构的调查结果,提出了考虑地域差异的分层次的食盐加碘量推荐值上限。研究表明,我国居民尿碘浓度分布有明显的区域性特征,尿碘浓度几何平均值和几何标准差分别为168.17和2.24μg·L-1,由于碘摄入过量导致的亚甲减发生率为4.00%。低水碘地区(水碘浓度低于150μg·L-1)的食盐加碘量推荐值上限为29.62mg·kg-1;中、高水碘地区(水碘浓度高于150μg·L-1)的居民通过非碘盐途径摄入的碘量已高于日可耐受最大摄入量,不宜再食用加碘食盐。这些结果基本支持了我国调整后的现行食盐加碘政策,即各地区根据当地人群实际碘营养水平,选定适合本地的食用盐加碘量。

Health Risk Assessment of Iodine Status in Chinese Residents

Due to great variation in the natural background levels of iodine found across China,the universal salt iodization(USI) policy,which lacks sufficient consideration on this regional variation,is not the most proper strategy for preventing and controlling iodine deficiency disease,and even may increase potential health risk caused by excessive iodine intake.Recently,the Ministry of Health(MOH) of China has amended the USI policy.However,it is still in urgent needs to evaluate and analyze this policy from a perspective of health risk assessment.In this paper,the iodine status of Chinese residents was assessed,and potential morbidity of subclinical hypothyroidism caused by excessive iodine intake in China was determined by integrating the distribution of urinary iodine concentrations of Chinese 8-10 year-old children,dose-response curves and threshold levels.Then the region-specific recommended iodine upper limits in edible salt were calculated based on the 5% benchmark dose,combined with the results of national dietary survey.Results showed that urinary iodine concentrations of national 8-10 year-old children varied greatly in different regions.The geometric mean value and geometric standard deviation were 168.17 and 2.24 μg·L-1,respectively.The morbidity of subclinical hypothyroidism induced by excessive iodine intake reached 4.00%.Recommended iodine upper limit in edible salt for regions with water iodine concentrations below 150 μg·L-1 was 29.62 mg·kg-1.However,for regions with water iodine concentrations above 150 μg·L-1,adequate iodine status has been achieved through intake pathways other than iodized salt,and thus there is no need to consume iodized salt for residents in those regions.These conclusions stay in support of the current salt iodization policy that region-specific iodine content in edible salt should be established according to iodine status of local residents.