碘盐新标准实施后对儿童和孕妇碘营养的影响

Effects of new standard iodized salt on iodine nutrition of children and pregnant women

目的了解2012年安徽省碘盐浓度由35 mg/kg调整为25 mg/kg后,来安县8~10岁儿童及孕妇碘营养状况变化趋势。方法选择来安县杨郢乡做为观察点,2012年供应新标准碘盐,即盐碘浓度25 mg/kg,实施后的1、2、3、6、9、12个月开展检测儿童及孕妇碘营养状况,随后于2014~2016年,在该乡镇每年进行1次随访,调查按时间顺序分别记为第1次、第2次、第3次、第4次、第5次、第6次、第7次、第8次和第9次调查。监测该乡镇1所小学200名8~10岁儿童,对其采集尿样和儿童家中的食用盐,进行尿碘和碘盐含量检测;并在该乡抽取孕妇50人进行尿碘和盐碘含量调查。结果儿童基线调查和第1~9次监测的8~10岁儿童家中盐碘中位数分别为29.2、23.2、22.1、23.8、23.2、23.6、22.4、22.5、23.0和22.2 mg/kg,基线与各次评估中,8~10岁儿童家庭食用盐碘含量差异均有统计学意义(P<0.001,校正后检验水准α=0.0028);基线调查和第1~9次评估8~10岁儿童尿碘中位数分别为335.2、279.2、306.6、337.3、260.8、274.9、196.0、220.4、241.1和159.4μg/L,8~10岁儿童基线尿碘浓度和第4~9次评估尿碘浓度差异均有统计学意义(P<0.001,校正后检验水准α=0.0028)。孕妇基线调查和第1~9次评估孕妇家中盐碘中位数分别为27.3、24.5、19.9、22.7、24.0、22.2、21.2、19.9、20.3和22.1 mg/kg,基线和各评估中,孕妇家庭食用盐碘含量差异均有统计学意义(P<0.001,校正后检验水准α=0.0028);基线调查和第1~9次评估孕妇尿碘中位数分别为300.7、-(缺失)、193.4、192.4、249.6、198.1、173.3、240.3、207.2和174.2μg/L,各次评估结果和基线结果相比,第4、5、7、8次评估中的孕妇尿碘浓度和基线孕妇尿碘浓度的差异无统计学意义(校正后检验水准α=0.0031)。结论新标准碘盐实施后8~10岁儿童碘营养水平由过量逐渐下降到适宜水平;孕妇碘营养水平由大于适宜量逐渐下降到适宜水平的下限。孕妇较儿童对食盐加碘标准下调更为敏感,存在碘营养不足的风险。

Objective To understand the trend of iodine nutritional status of 8-10 year-old children and pregnant women in Lai’an County after the concentration of iodized salt in Anhui Province was adjusted from 35 mg/kg to 25 mg/kg in 2012.Methods Yangying Township of Lai’an County was selected as the observation point.A new standard iodized salt was supplied in 2012,i.e.salt iodine concentration of 25 mg/kg.The iodine nutritional status of children and pregnant women was tested at 1, 2, 3, 6, 9 and 12 months after implementation.From 2014 to 2016, a follow-up survey was carried out annually in this town.The survey was recorded as the first and second in time sequence.The second, third, fourth, fifth, sixth, seventh, eighth and ninth surveys were conducted.200 children aged 8-10 years old in a primary school in this town were monitored.Urine samples and salt in children’s homes were collected for detection of urinary iodine and iodized salt content, and 50 pregnant women were sampled in this township for investigation of urinary iodine and salt iodine content.Results In the baseline survey of children and these 9 monitoring assessments, the median values of salt iodine in the home of children aged 8 to 10 years were 29.2, 23.2, 22.1, 23.8, 23.2, 23.6, 22.4, 22.5, 23.0 and 22.2 mg/kg, respectively. There were significant differences in salt iodine content between children aged 8 to 10 years and between the baseline and each evaluation(P< 0.001, after correction test level a = 0.0028). The median urinary iodine levels of children aged 8-10 years in baseline survey and the first to ninth evaluation were 335.2, 279.2, 306.6, 337.3, 260.8, 274.9, 196.0, 220.4, 241.1 and 159.4 μg/L, respectively. There were significant differences in urinary iodine concentrations of children aged 8-10 years between baseline and 4 th to 9 th assessments.(P<0.001, after correction test level a=0.0028). The median values of salt iodine in the home of pregnant women were 27.3, 24.5, 19.9, 22.7, 24.0, 22.2, 21.2, 19.9, 20.3 and 22.1 mg/kg in the baseline survey and the first-to-ninth evaluation, respectively. The difference of salt iodine content in the home of pregnant women was statistically significant between the baseline survey and each evaluation(P< 0.001, adjusted test level a= 0.0028).The median urinary iodine of pregnant women in baseline survey and the first to ninth evaluation were 300.7,-(missing)、 193.4, 192.4, 249.6, 198.1, 173.3, 240.3, 207.2 and 174.2 ug/L, respectively.Compared with baseline results, there was no significant difference in urinary iodine concentration between pregnant women in the 4 th, 5 th, 7 th and 8 th evaluation and baseline pregnant women(adjusted test level a=0.0031).Conclusion After the implementation of the new iodized salt standard,the iodine nutrition level of children aged 8-10 gradually decreased to the appropriate level and the iodine nutrition level of pregnant women decreased gradually from greater than the appropriate amount to the lower limit of the suitable level.According to this result, pregnant women were more sensitive than children to the lowering of salt iodization standards, and they have a risk of insufficient iodine nutrition.