The Research On Iodine Requirement Of Chinese Lactating Women

Objective: There are lack of direct research data about the iodine requirement of lactating women in China.This study aimed to re-estimate the average iodine loss in breast milk of Chinese lactating women by the infant text-weighing study and then to explore the EAR of iodine of lactating women based on Chinese direct/local study.Methods: This study was conducted in Tianjin city and Luoyang city which both were in adequate iodine status.Seventy exclusively breastfeeding mothers who were1 to 6 months postpartum and their infants were selected based on the basic information survey,thyroid function screening in mothers and the growth and development assessment in infants.A 4-day study was conducted in the eligible mother-infant pairs.During the 4 test-weighing study,infants were weighed before and after each feed for a 24-h period every day.The sum of each infant's weight gain of each feed within 24 h was calculated as the all-day breast milk loss of each lactating woman;a 5-ml breast milk sample was collected from each lactating woman before and after each feed,respectively to determine the iodine concentration in breast milk.Then,the average breast milk iodine loss and the iodine EAR in Chinese lactating women were estimated.In addition,24-h urine samples were collected from each lactating women everyday to determine the urinary iodine concentration;24 h dietary records were performed by each lactating women for measuring their dietary iodine intake.Results: 1.of the 70 mother-infant pairs included into this study,54 pairs completed the whole study.Of the 54 mother-infant pairs,25 were from Tianjin and the remainder from Luoyang.Except for the family annual income(Z=-3.755,P<0.001),there were no statistically significant differences in the other demographic data of the mother-infant pairs between Tianjin city and Luoyang city(all P>0.05).2.The average dietary iodine intake of the lactating women in this study was 328.05 ?g/d and there was no statistically significant difference in the average dietary iodine intake between Tianjin city and Luoyang city(t=0.911,P=0.367).88.9% of the mothers had daily iodine intake between the RNI and UL and 11.1% lower than the RNI.The daily iodine intake of the lactating women from salt,food and drinkingwater accounted for 51.9%,39.1% and 9.0% of the total daily iodine intake,respectively.3.The median urinary concentration(24h-UIC)of the lactating women in this study was 135.10 ?g/L and there was no statistically significant difference in the median 24h-UIC between Tianjin city and Luoyang city(Z=-0.432,P=0.666).In addition,Of the 54 mothers,22.2% had 24h-UIC<100 ?g/L.4.The median iodine concentration in breast milk(BMIC)of the lactating women was 153.72 ?g/L and there was no statistically significant difference in the median BMIC between Tianjin city and Luoyang city(Z=-0.352,P=0.735).Univariate analysis revealed that BMIC was associated with maternal weight(r=0.308,P=0.023),maternal daily dietary iodine intake(r=0.568,P<0.001),maternal UIC(r=0.296,P=0.030)and the age of infants(r=-0.573,P<0.001).The multiple linear regression analysis showed that the maternal daily dietary iodine intake and the age of the infants statistically correlated with BMIC.5.The average loss of breast milk of the lactating women in this study was 711 mL/d and there was no statistically significant difference in the average daily breast milk loss between Tianjin city and Luoyang city(t=1.148,P=0.252).The daily maternal breast milk loss were positively associated with age of infants(r=0.496,P<0.001)and feeding frequency within 24 h(r=0.335,P=0.013).6.The mean iodine loss in human milk of lactating women was 108.17 ?g/d.7.The EAR and RNI of iodine in the lactating women was 218.67 ?g/d and 306.14 ?g/d,respectively.Conclusions: 1.Without taking iodine supplements,the overall iodine nutrition status of lactating women in Tianjin and Luoyang was adequate and appropriate.However,there were still some people were at risk for iodine deficiency.2.In the current situation of iodine in the general population,the daily amount of iodine losses in breast milk of Chinese lactating women was 108.17 ?g/d,higher than the value used to set the current iodine EAR of lactating women(85 ?g/d).3.The EAR and RNI of iodine in Chinese lactating women is 218.67 ?g/d and 306.14 ?g/d,respectively,higher than that set in 2013 Chinese DRIs(170 ?g/d and 240 ?g/d).