Iodine Concentration in the Breast Milk and Urine as Biomarkers of Iodine Nutritional Status of Lactating Women and Breastfed Infants in Taiwan

• Published in: Nutrients Vol. 15; no. 19; p. 4125
• Main Authors: Huang, Chun-Jui, Li, Jia-Zhen, Hwu, Chii-Min, Chen, Harn-Shen, Wang, Fan-Fen, Yeh, Chang-Ching, Yang, Chen-Chang
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 25.09.2023; MDPI
• Subjects: Babies; Biological markers; Biomarkers; Breast feeding; breast milk; Breastfeeding & lactation; Dairy products; Food; inductively coupled plasma mass spectrometry; Infants; Iodine; lactation; Milk; Nutritional status; Pregnant women; Questionnaires; Reference materials; Regression analysis; Seafood; thyroid; Thyroid gland; urinary iodine concentration; Urine; Vitamins; Taiwan; United States > US; Germany
• ISSN: 2072-6643; 2072-6643
• DOI: 10.3390/nu15194125

Breast milk iodine concentration (BMIC) can be different when median urinary iodine concentration (UIC) is similar. The BMIC, UIC/creatinine (Cr), estimated 24-h urinary iodine excretion (24-h UIE) of lactating women in Taiwan is unknown. This study enrolled lactating women from Taipei Veterans General Hospital (August 2021–February 2023). Each participant provided a random spot urine sample, two breast milk samples, a blood sample, and completed a food frequency questionnaire on the same day. Iodine measurement was performed by inductively coupled plasma mass spectrometry. The median UIC of the enrolled 71 women was 91.1 μg/L, indicating insufficient iodine status; however, the median BMIC was 166.6 μg/L and this suggested that the amount of iodine delivered through breast milk was adequate for the breastfed infants. BMIC was correlated with UIC/Cr and 24-h UIE (both rs = 0.49) but not with UIC (rs = 0.18) or thyroid stimulating hormone (rs = 0.07). Women who did not consume dairy products (adjusted odds ratio: 24.41, 95% confidence interval: 1.26–471.2) and multivitamins (adjusted odds ratio: 8.26, 95% confidence interval: 1.76–38.79) were at increased odds for having lower BMIC. The results suggest that measuring maternal UIC alone may not be sufficient, as BMIC, UIC/Cr, and 24-h UIE are all important biomarkers. Ingestion of dairy products and multivitamins were independently associated with BMIC.