A cross-sectional study of urinary iodine and salt iodine content among schoolchildren and their families in Haimen City, Jiangsu Province

Abstract

Objective To understand the level of urinary iodine of schoolchildren and salt iodine content of their families in a primary school and to analysis influence between salt iodine content and urinary iodine level in Haimen City,Jiangsu Province.Methods A cross-sectional study was conducted in a primary school of Haimen City in 2012.With the method of stratified cluster sampling,all students aged 9 ～ 12 were extracted in grades 3-5,urine samples and salt samples of their family were collected.Urinary iodine and salt iodine were determined according to ＂Method for Determination of Iodine in Urine by As3＋-Ce4＋ Catalytic Spectrophotometry＂ （WS/T 107-2006） and ＂Direct Titration of Universal Test method in Salt Industry＂ （GB/T 13025.7-1999）.Results Totally,452 students from grades 3-5,including 233 boys and 219 girls were selected by cluster-stratified sampling.The median of children＆#39;s urinary iodine was 231.90 μg/L,while the median of boys and girls was 235.40 and 222.60 μg/L,respectively.The median of urinary iodine of 9,10,11 and 12 year old students was 253.65,195.70,236.40 and 241.70 μg/L,respectively.The proportion of less than 100 μg/L and ≥300 μg/L was 7.7% （35/452） and 27.7% （125/452）,respectively.There were no significant differences between different gender and age students.Among the 452 salt samples collected the median of salt iodine was 27.50 mg/kg.The coverage rate of iodized salt,the qualified rate of iodized salt and the intake rate of qualified iodized salt were 98.9% （447/452）,95.1% （425/447） and 94.0% （425/452）,respectively.After consumptionn of non-iodized salt （〈 5 mg/kg）,unqualified iodized salt（5 ～ 〈 20 mg/kg or 〉 50 mg/kg） or qualified iodized salt [（35 ± 15）mg/kg],the median of urinary iodine of children was 177.30,211.95 and 232.90 μg/L,respectively.Correlation analysis showed that there was no relationship between iodine content of salt and urinary iodine level of schoolchildren （r =0.085,P 〉 0.05）.Conclusions Current nutritional level of schoolchildren in Haimen City is higher than the appropriate amount.Household salt iodine content of edible salt does not affect urinary iodine level of the children significantly. Key words: Cross-sectional study; Children; Urinary iodine; Salt iodine