An investigation of the source and the nutritional status of iodine after termination of iodized salt supply in high water iodine areas in Shanxi province / 中国地方病学杂志

ABSTRACT

Objective To study the changes of iodine source and the nutritional status of iodine after termination of iodized salt supply in the areas with different water iodine concentrations in Shanxi province,in order to provide scientific bases for developing strategies on control and prevention of iodine deficiency disorders,and to study the cut-off value of water iodine level where iodized salt supply should be stopped.Methods In 2010 in Shanxi province,6 villages with 100％ of non-iodized salt consumption rate were selected as the survey spots based on the iodine concentration in drinking water of 0-,50-,100-,150-,300-,≥500 μg/L.Villages'iodized salt supply was terminated thoroughly.In each village,20 children aged 8 to 10 were selected.At the same time,women of childbearing age 18 to 50 years old and adult men aged 18 to 60 were selected from the same families as the children.Diet surveys were conducted by the method of 3 days recall on all subjects.Drinking water samples,staple foods,supplementary foods and urinary samples of all subjects were collected and the iodine concentration was determined by arsenic-cerium catalytic spectrophotometry.Results ①In the villages of water iodine 25.9,70.6 μg/L,the medians urinary iodine of children,women and men were all ranged from 100 to 199 μg/L,which meant their iodine nutrition levels were appropriate.In the village of water iodine 109.0 μg/L,the medians urinary iodine of children,women and men were all ranged from 200 to 299 μg/L,which meant their iodine nutrition levels were more than appropriate.In the villages of water iodine 225.8,430.0,581.2 μg/L,the medians urinary iodine of children,women and men were all ≥ 300 μg/L,which meant their iodine nutrition levels were too high.②)In all the 6 villages,the intaking amount of iodine met and exceeded the standard recommended intake of dietary iodine by ICCIDD/UNICEF/WHO (8 to 10-year-old children ≥ 120 μg/d,women of childbearing age and adult men ≥ 150 μg/d).But in the village of water iodine 581.2 μg/L,the iodine intake was exceeded the daily maximum safe intake (children aged 8 to 10 ≤800 μg/d,women of childbearing age and adult man ≤ 1000 μg/d).③The amount of iodine ingestion from drinking water was increased with the water content of iodine.When water iodine exceeded 100 μg/L,the amount of iodine ingestion from drinking water was higher than from food intaking,and became a main resource of iodine in the human body.Conclusions In the counties of iodine concentration in drinking water above 100 μg/L in high iodine areas of Shanxi province,the water iodine becomes the most important source of iodine,and iodine nutritional level is more than appropriate or possible excess.It is recommended that in areas of high water iodine of Shanxi province,the standard cut-point of water iodine value is set to 100 μg/L.