An investigation on iodine nutritional status of lactating women and infants (0-2 years old) in different ecological regions of Gansu Province / 中华地方病学杂志

ABSTRACT

Objective To assess iodine nutritional status of lactating women and infants (0-2 years old) in six ecological regions of Gansu Province,and to provide a scientific basis for iodine supplementation of target people.Methods According to different topography and climate conditions,Gansu Province was divided into six ecological regionsthe desert region,the Gobi region of Hexi Corridor,the hills and valleys region of Loess Plateau,the Zhongshan Valley of Qinling Mountains,the grassland meadow area of Gannan plateau and the Loess Plateaugully region.Totally 5 counties were selected from each ecological region,and each county was divided into five geographic locations (east,south,west,north and center).In each location,one township was identified and ten samples of lactating women and infants (0-2 years old) were selected randomly and 60 salt samples of residents were collected to determine iodine content.At the same time salt intake of 20 residents was surveyed in three townships as mentioned above.The water samples of all the centralized water supply projects were collected in each county,and one water sample of the decentralized water supply in ten townships with the largest population of each county from east,south,west,north and center locations was collected to determine iodine content.One soil sample was collected to determine iodine content in east,south,west,north and center townships of each county.The urinary iodine and water iodine levels were measured with the method for determination of iodine in urine by As3+-Ce4+ catalytic spectrophotometry (WS/T 107-2006).The direct titration method among thegeneric methods for iodide testing in salt production industry (GB/T 13025.7-2012) was used to determine the salt iodine level,and the arbitration method was adopted for quantitative determination in the case of Sichuan salt or other special salts and the salt intake was estimated based on three day weighed food record.The soil iodine was determined using the amplified colorimetric method.Results Totally 1 476 and 1 461 urine samples of lactating women and infants were collected,and the total urine iodine medians of lactating women and infants (0-2 years old) were 149.05 and 151.34 μg/L,respectively,the urine iodine median of lactating women and infants in each ecological region was at the 100-199 μg/L appropriate level.Not weaning infants urine iodine (155.32 μg/L) was higher than that of the weaning infants (146.30 μg/L),the difference was significant statistically (Z =-2.808,P ＜ 0.05).There was a correlation between urine iodine of not weaning infants aged 0-2 years old and breastfeeding women (r =0.133,P ＜ 0.01),and there was no correlation between weaning infants and breastfeeding women (r =0.045,P ＞ 0.05).About 9 008 salt samples were collected,and the rates of qualified iodized salt intake in the six ecological regions were all higher than 93％.The daily salt intake per person ranged from 4.5 g to 12.6 g,in which the Loess Plateaugully region was the highest with 12.6 g and the grassland meadow area of Gannan plateau was the lowest with 4.5 g.The water iodine median of 1 513 water samples was 3.3 μg/L.The water iodine medians of the rest 4 ecological regions were all less than 5 μg/L except for the desert region (42.4 μg/L) and the Loess Plateau-gully region (30.0 μg/L) of which the median of water iodine was higher than 20 μg/L.The soil iodine median of 155 soil samples was 127 μg/kg,in which the desert region was the lowest with 78 μg/kg and the grassland meadow area of Gannan plateau was the highest with 218 μg/kg.Conclusion Lactating women and infants are in good iodine nutritional status and the present iodized salt concentration can meet the demand of iodine nutrition of lactating women and infants well.