Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Key Laboratory of Environmental Nutrition and Population Health, Tianjin Medical University, Tianjin, China.
Department of Hand Microsurgery, Tianjin Hospital, Tianjin, China.
J Nutr. 2023 Jan;153(1):208-214. doi: 10.1016/j.tjnut.2022.11.024. Epub 2022 Dec 26.
Adequate breast milk iodine concentration (BMIC) is essential for the growth and cognitive development of exclusively breastfed infants; however, data on variations in BMIC over 24 h are limited.
We aimed to explore in lactating women the variation in 24-h BMIC.
Thirty pairs of mothers and breastfed infants aged 0-6 mo were recruited from the cities of Tianjin and Luoyang, China. A 3-d 24-h dietary record, including salt intake, was performed to assess the dietary iodine intake of lactating women. Breast milk samples before and after each feeding for 24 h and 24-h urine samples were collected from the women for 3 d to estimate iodine excretion. A multivariate linear regression model was used to analyze the factors influencing BMIC. A total of 2658 breast milk samples and 90 24-h urine samples were collected.
The median BMIC and 24-h urine iodine concentration (UIC) of lactating women for a mean of 3.6 ± 1.48 mo were 158 μg/L and 137 μg/L, respectively. The interindividual variability of BMIC (35.1%) was higher than that observed within individuals (11.8%). The variation in BMIC showed a "V" shaped curve over 24 h. The median BMIC at 08:00-12:00 (137 μg/L) was significantly lower than that at 20:00-24:00 (163 μg/L) and 00:00-04:00 (164 μg/L). A progressively increasing curve was obtained for BMIC until it peaked at 20:00 and plateaued at a higher concentration from 20:00 to 04:00 than at 08:00-12:00 (all P < 0.05). BMIC was associated with dietary iodine intake (β: 0.366; 95% CI: 0.004, 0.018) and infant age (β: -0.432; 95% CI: -1.07, -0.322).
Our study shows that the BMIC presents a "V" shaped curve over 24 h. We recommend that breast milk samples be collected between 08:00 and 12:00 for evaluation of the iodine status of lactating women.
母乳碘浓度（BMIC）充足对纯母乳喂养婴儿的生长和认知发育至关重要；然而，关于 24 小时内 BMIC 变化的数据有限。
本研究旨在探讨哺乳期妇女 24 小时内 BMIC 的变化。
我们从中国天津和洛阳的城市中招募了 30 对 0-6 月龄的母婴。进行了为期 3 天的 24 小时膳食记录，包括盐摄入量，以评估哺乳期妇女的膳食碘摄入量。从这些女性身上采集了 24 小时内每餐前和餐后的母乳样本以及 24 小时尿液样本，以估计碘排泄量。采用多元线性回归模型分析影响 BMIC 的因素。共采集了 2658 份母乳样本和 90 份 24 小时尿液样本。
平均随访 3.6±1.48 个月时，哺乳期妇女的中位 BMIC 和 24 小时尿碘浓度（UIC）分别为 158μg/L 和 137μg/L。BMIC 的个体间变异性（35.1%）高于个体内变异性（11.8%）。24 小时内 BMIC 呈“V”形曲线变化。8:00-12:00 时的中位 BMIC（137μg/L）明显低于 20:00-24:00 时（163μg/L）和 00:00-04:00 时（164μg/L）。BMIC 呈逐渐增加的曲线，20:00 时达到峰值，20:00 至 04:00 时的浓度高于 8:00-12:00 时（均 P<0.05）。BMIC 与膳食碘摄入量（β：0.366；95%CI：0.004，0.018）和婴儿年龄（β：-0.432；95%CI：-1.07，-0.322）相关。
本研究表明，BMIC 在 24 小时内呈“V”形曲线。我们建议在评估哺乳期妇女的碘状况时，应在 8:00-12:00 之间采集母乳样本。
