Survey and evaluation of iodine nutritional status of different populations in Harbin city in 2011

Objective To investigate current iodine nutritional status of different groups of people in Harbin city, and to provide the basis for development of salt iodization standard and scientific iodine supplementation.Methods Three urban districts and three surrounding counties were chosen in Harbin,2011.In each chosen urban district and county,one district office (township) was selected,and one residents committee (village) was chosen in each of the district office(township),and 30 households were selected by systematic sampling.Iodized salt,water iodine and iodine intake per capita were investigated.In each of the residents committee (village),20 adults aged 18 - 45,30 pregnant women or lactating women,and 100 school children aged 8 - 10 were selected.Urine samples were collected and urinary iodine level were tested.Salt iodine was determined by direct titration,water and urinary iodine by arsenic cerium catalytic spectrophotometry.Iodine uptake and iodine nutritional status of different populations in Harbin urban and rural areas were compared.Results The edible rate of qunlified iodized salt were 93.3％(84/90) and 96.3％(156/162) in Harbin urban and rural residents,respectively,which were all greater than 90％,and the highest value of salt iodine were 38.3,46.0 mg/kg,respectively,in urban and rural areas,which all did not exceed the upper limit(50 mg/kg) of qualified iodized salt,but there were some samples of salt iodine content below the national standard(20 mg/kg).Water iodine value in urban and rural areas,even the highest value(9.40,8.40 μg/L),was failed to meet the national standard 10 μg/L; salt eaten by rural people perperson a day(8.33 g) was significantly higher than that of the urban people(7.03 g,Z=- 2.750,P ＜ 0.01); in addition to rural children aged 8 - 10,whose urinary iodine value(228.6 μg/L) was higher,the values in urban and rural adults ( 111.3,195.6 μg/L),pregnant women ( 193.0,172.9 μg/L),lactating women ( 128.4,173.7 μg/L)and urban children ( 186.8 μg/L ) were all in appropriate level.The urinary iodine medians ( 195.6,228.6 μg/L )of adults and children in rural were significantly higher than that of urban adults and children(111.3,186.8 μg/L,Z =- 2.294,- 5.434,P ＜ 0.05 or ＜ 0.01,respectively).Population composition of iodine deficiency in both urban and rural adults,lactating and pregnant women[46.7％(28/60),21.6％(13/60) ; 21.1％(19/90),21.3％ (18/89) ; 27.8％ ( 25/90 ),42.2％ (38/90) ] were significantly higher than that of the population composition with iodine excess[4.6％(4/60),5.0％(3/60) ; 16.7％(15/90),16.9％(15/89) ; 4.4％(4/90),0.0％(0/90)],but proportion of iodine excessive population in rural children [26.3％(79/300)] was significantly higher than proportion of iodine deficiency[5.6％(17/300)].Conclusions The natural environment of Harbin city is still in the iodinedeficient state.In addition to children in rural areas,the iodine intake and iodine nutrition level is basically appropriate; the risk of disease caused by iodine deficiency in adults,lactating and pregnant women is higher than by iodine excess,but the situation of children in rural is on the opposite.Therefore,we should strengthen the monitoring of different populations,and supplement iodine scientifically based on their need. Key words: Iodine; Nutritional status; Adults; Child; Pregnant women; Lactating women