Estimation of appropriate dietary intake of iodine among lactating women in China based on iodine loss in breast milk.

Abstract

Data on iodine loss in breast milk, which are critical for establishing the appropriate dietary iodine intake for lactating women, is currently limited. A study was conducted to assess iodine loss in breast milk among Chinese lactating women to estimate the appropriate dietary intake of iodine. A total of 54 pairs of healthy, lactating women and their infants aged 0-6months were recruited from Tianjin and Luoyang cities in China. A 4days infant weighing study was conducted to assess iodine loss in the breast milk of lactating women. Mothers were required to weigh and record their infants' body weights before and after each feeding for a 24h period from 8:00 am to 8:00 am. During the weighing study, 2812 breast milk samples and 216 24-h urine samples were collected from each lactating mother for four consecutive days. In addition, a 3days 24h dietary record, including salt weighing and drinking water samples collecting, was performed by each lactating mother to determine dietary iodine intake during the weighing study. The average dietary iodine intake of lactating women was 323 ± 80μg/d. The median breast milk iodine concentration and 24h urinary iodine concentration of lactating women were 154 (122-181) and 135 (104-172)μg/L, respectively. The mean volume of breast milk and the mean iodine loss in the breast milk of lactating women were 711 ± 157mL/d and 112 ± 47μg/d, respectively. The appropriate dietary intake of iodine among lactating Chinese women is approximately 260µg/d. Based on the iodine loss in breast milk (110μg/d) found in this study, and the estimated average requirement of iodine for adults, the appropriate dietary intake of iodine among lactating Chinese women is 260µg/d, which is higher than the 240μg/d recommended by the China Nutrition Science Congress in 2013.