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Estimation of iodine nutrition status among lactating women with adequate iodine based on fractional iodine excretion in urine

Published online by Cambridge University Press:  12 August 2025

Ying Zhang ,
Xin Zhao ,
Haohao Meng ,
Xiaomin Jia ,
Zixuan Zhang ,
Zhencheng Zuo ,
Xiangjing He ,
Peixuan Wu ,
Xinze Jiang  and
Wanqi Zhang Open the ORCID record for Wanqi Zhang [Opens in a new window]
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Ying Zhang
Affiliation:
Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Key Laboratory of Environmental Nutrition and Population Health, Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, Tianjin Medical University, Tianjin, China
Xin Zhao
Affiliation:
Department of Hand Microsurgery, Tianjin Hospital, Tianjin, China
Haohao Meng
Affiliation:
Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Key Laboratory of Environmental Nutrition and Population Health, Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, Tianjin Medical University, Tianjin, China
Xiaomin Jia
Affiliation:
Qingdao Center for Disease Control and Prevention, Qingdao City, China
Zixuan Zhang
Affiliation:
Department of Preventive Medicine Specialty, School of Public Health, Jilin University, Changchun City, China
Zhencheng Zuo
Affiliation:
Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Key Laboratory of Environmental Nutrition and Population Health, Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, Tianjin Medical University, Tianjin, China
Xiangjing He
Affiliation:
Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Key Laboratory of Environmental Nutrition and Population Health, Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, Tianjin Medical University, Tianjin, China
Peixuan Wu
Affiliation:
Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Key Laboratory of Environmental Nutrition and Population Health, Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, Tianjin Medical University, Tianjin, China
Xinze Jiang
Affiliation:
Department of Clinical Medicine Specialty, The Second School of Clinical Medicine, Tianjin Medical University, Tianjin, China
Wanqi Zhang*
Affiliation:
Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Key Laboratory of Environmental Nutrition and Population Health, Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, Tianjin Medical University, Tianjin, China
Zhongna Sang*
Affiliation:
Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Key Laboratory of Environmental Nutrition and Population Health, Key Laboratory of Prevention and Control of Major Diseases in the Population, Ministry of Education, Tianjin Medical University, Tianjin, China
*
Corresponding authors: Wanqi Zhang; Email: wqzhang@tmu.edu.cn, Zhongna Sang; Email: sangzhongna@tmu.edu.cn
Corresponding authors: Wanqi Zhang; Email: wqzhang@tmu.edu.cn, Zhongna Sang; Email: sangzhongna@tmu.edu.cn
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Abstract

Data on the distribution of iodine in the urine and breast milk of lactating women are limited. This study aimed to establish a formula to assess iodine status in lactating women by evaluating the fractional iodine excretion in urine and breast milk. A 3-d 24-h iodine metabolism survey in 2021–2023 was conducted on fifty-four pairs of lactating women and infants in Tianjin and Luoyang, China. We used the 24-h dietary record and salt weighing method to assess daily iodine intake (DII). Iodine excretion in breast milk and urine was measured. The median 24-h urinary iodine concentration and breast milk iodine concentration were 135·06 μg/L and 150·26 µg/L, respectively. When the DII was between 240 μg/d and 600 μg/d, the predicted value of fractional breast milk iodine excretion was 31·48 % (95 % CI: 27·16 %, 36·22 %). When the daily iodine excretion was between 258 μg/d and 476 μg/d, the fractional urine iodine excretion (59·09 %) and fractional breast milk iodine excretion (40·91 %) were stable. DII can be derived from the spot urinary iodine concentration as follows: urinary iodine concentration (μg/L) × (0·0009 L/h/kg × 24 h/d) × body weight (kg) ÷ 0·59 ÷ 0·94 = DII (μg/d). In conclusion, lactating women with adequate iodine delivered approximately 31·48 % of the DII to their infants. A stable proportion (59·09 %) of iodine excretion was discharged through urine, which was used to assess the iodine status based on the spot urinary iodine concentration of lactating women. This study was registered at ClinicalTrials.gov (NCT04492657).

Keywords

Iodine intakeLactating womenUrinary iodine excretionBreast milk iodine

Information

Type
Research Article
Information
British Journal of Nutrition , Volume 134 , Issue 4 , 28 August 2025 , pp. 297 - 303
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Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of the Nutrition Society

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Footnotes

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Ying Zhang, Xin Zhao and Haohao Meng contributed equally to this work.

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