Iodine, selenium, iron and zinc intake in 5- to 10-month-old infants living in Manawatū, Aotearoa : Mother and Infant Nutrition Investigation (MINI) study : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nutrition and Dietetics at Massey University, Tāmaki Makaurau, Aotearoa
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Date
2021
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Massey University
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Abstract
Objective: Optimal thyroid function is essential for growth and development in early life, This study will nvestigate iodine, selenium, iron, and zinc intake in 5 to 10 month old infants living in Manawatū, Aotearoa, as they have been shown to support optimal thyroid function. Method: This study is part of an observational longitudinal study conducted in Manawatū, Aotearoa from June 2016 – December 2017. Eighty-seven breastfed infants between 5 and 10 months old and their mothers attended a study visit at the Massey University Manawatū Campus. Fifity-one mothers recorded a three-day diet diary (3DDD) for their infants' food and fluid intake, and breastfeeding occasions. Seventy-two maternal breastmilk samples and 41 infant spot urine samples were analysed for iodine and selenium concentrations using inductively-coupled plasma mass spectrometry. Results: Median (Q1, Q3) intake for iodine using 3DDD was 62 (30, 98) µg/day with 82% of infants below their age-specific Adequate Intake (AI). Median urinary iodine concentration (MUIC) was 107 (57.5, 198) µg/L with only 12% below 50 µg/L therefore most of the infants could be classified as iodine insufficient according to the WHO/UNICEF/ICCDD (2007) criteria. However, if MUIC is measured against higher cut-offs extrapolated from the AI, such as 125 µg/L, the iodine status of more of population could be considered suboptimal. Maternal breast milk iodine concentration (BMIC) was 59 (39, 108.5) µg/L, contributing a median 37 (6, 9) µg/day to total iodine intake in breastfed infants. Median infant selenium intake was 12 (9, 16) µg/day selenium intake, with 67% below their age-specific AI. Median urinary selenium concentration (MUSC) in infants was 11 (6, 16) µg/L. Breastmilk selenium concentration (BMSC) was 11 (9, 13) µg/L, contributing a median 7 (6, 9) µg/day to total selenium intake in breastfed infants. Median infant intake of iron was 2 (1, 5) mg/day with 78% below age specific EAR/AI. Median infant intake of zinc was 3 (2, 4) mg/day, with 31% below their age specific EAR/AI and 16% exceeding upper limit (UL) for zinc intake. In addition to complementary food, 69% of infants had only breastmilk, 23% had combination of breastmilk and infant formula, and 8% had only infant formula. One infant was not yet receiving complementary food. Conclusion: Despite public health initiatives, this study suggests infants in Aotearoa still have suboptimal intake of iodine, zinc and iron While some infants are achieving low or adequate zinc intakes, others are consuming excessive zinc, however the associated risks are low. Suboptimal intake of iodine, selenium, iron and zinc in the infant diet could impact thyroid function, growth, and neurodevelopment.
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