IODINE NUTRITION STATUS OF POPULATION IN THE AREAS WITH DIFFERENT IODINE CONCENTRATIONS OF DRINKING WATER

Objective:To study the master iodine nutrition status of population living in areas with different iodine in drinking water and the cut-off point of stopping iodized salt supply and the range of adequate iodine intake for the strategy of prevention from iodine deficiency or excess. Method:Thirteen townships points along the Yellow River downstream in Shandong were investigated and divided into six groups(A-F) based on water iodine concentrations of 0-50,50-100,100-150,150-300,300-800 and over 800 μg/L. The indicators of water iodine,edible salt iodine,urinary iodine(UI) and thyroid goiter were observed. Results:From A,B,C,D,E and F group,the medians of water iodine concentration were 20.3,91.4,143.2,203.6,341.9 and 812.3 μg/L,of edible salt iodine were 0,25.7,25.8,30.4,36.4 and 33.0 mg/kg,and of UI were 116.8,354.2,400.4,607.9,881.3 and 1 213.8 μg/L respectively. The goiter rates were 10.8,8.6,15.0,14.2,14.9 and 25.0 % respectively . The sample proportion of UI below 100 μg/L was 8.2%,of 100-300 μg/L was 18.2% and of over 300 μg/L was 73.6%. Frequency excursion of UI had a high trend towards water iodine concentration over 90μg/L in 5 groups. The proportion of UI over 300 μg/L increased,consistent with higher water iodine level. Median UI of all groups with iodized salt decreased significantly,especially group F. There were significant correlations between UI and water iodine. Iodine nutrition status was markedly excessive in group B,C,D,E and F. Conclusions:Iodine nutrition status of most residents consuming drinking water with iodine concentration about 20 μg/L should be adequately supplied with eligible iodized salt. Iodine intakes in groups B-F were excessive,and iodized salt supply should be stopped there. The cut-point of water iodine level where iodized salt stopped could possibly be 90 μg/L,and the range of adequate iodine intake,in terms of drinking water,could be defined at range of over 20 to 90 μg/L in iodine concentration.