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Background: Most pregnant or lactating women in Canada will not meet iodine requirements without iodine supplementation., Objectives: To assess the iodine status of 132 mother-infant pairs based on secondary analyses of a vitamin D supplementation trial in breastfed infants from Montréal, Canada., Methods: Maternal iodine status was assessed using the breastmilk iodine concentration (BMIC). Singleton, term-born infants were studied from 1-36 months of age. Usual (adjusted for within-person variation) iodine intakes were estimated from urinary iodine and creatinine concentrations. Iodine status was assessed using median urinary iodine concentrations (UICs) and by estimating inadequate intakes by the cut-point method using a proposed Estimated Average Requirement for infants 0-6 months of age (72 μg/d)., Results: At 1, 3, and 6 months of age, 70%, 63%, and 3% of infants, respectively, were exclusively breastfed. From 1-36 months of age (n = 82-129), the median UICs were ≥100 μg/L (range, 246-403 μg/L), which is the cutoff for adequate intakes set by the WHO for children <2 years. Almost all (98%-99%) infants at 1 and 2 months, 2 and 3 months, and 3 and 6 months of age had usual creatinine-adjusted iodine intakes ≥ 72 μg/d. The median BMIC was higher (P < 0.001) at 1 month compared to 6 months of lactation [1 month, 198 μg/kg (IQR, 124-274; n = 105) and 6 months, 109 μg/kg (IQR, 67-168; n = 78)]. At 1 and 6 months, 96% and 79% of mothers, respectively, had a BMIC ≥ 60 μg/kg, the lower limit of a normal reference range. The percentages of mothers that used a multivitamin-mineral (MVM) supplement containing iodine were 90% in pregnancy and 79% and 59% at 1 and 6 months of lactation, respectively., Conclusions: The iodine status of infants was adequate throughout infancy. These results support a recommendation that all women who could become pregnant, who are pregnant, or who are breastfeeding take a daily MVM supplement containing iodine., (© The Author(s) 2022. Published by Oxford University Press on behalf of the American Society for Nutrition.)

Background: Adequate iodine intake is important for children and women of childbearing age because iodine is vital for fetal brain development and early life., Objective: Iodine status of children (n = 1875), adolescents (n = 557), and women of childbearing age (n = 567) was assessed using urinary iodine concentrations (UIC) from duplicate spot samples collected in the Canadian Health Measures Survey, cycle 5 (2016-2017)., Methods: Daily iodine intakes were estimated from urinary iodine and creatinine concentrations using a formula based on iodine absorption and predicted 24-h creatinine excretion. Usual UIC and iodine intakes, adjusted for within-person variation, were estimated using the National Cancer Institute method. Iodine status was assessed by 1) comparing median UIC with WHO/UNICEF/ICCIDD reference ranges and 2) estimating the prevalence of inadequate and excessive intakes using the estimated average requirement (EAR) and tolerable upper intake level (UL) cut-point method, respectively., Results: Median UIC for males and females 6-11 or 12-19 y old were ≥100 μg/L, the lower cutoff for adequate intakes. For women 20-39 y old, the median UIC of an unadjusted sample was 81 μg/L (95% CI: 67, 95) and for the usual UIC was 108 μg/L (95% CI: 84, 131). The percentage of children 3 y old with iodine intake ≥EAR was 82% (95% CI: 75, 89). The corresponding estimates for males 4-8, 9-13, and 14-18 y old were 93% (95% CI: 88, 97), 91% (95% CI: 87, 96), and 84% (95% CI: 76, 91), respectively. Estimates for females 4-8, 9-13, 14-18, and 19-39 y old were 86% (95% CI: 83, 89), 87% (95% CI: 80, 95), 68% (95% CI: 55, 80), and 68% (95% CI: 59, 76), respectively. For all sex-age groups, 91-100% had iodine intakes ≤UL., Conclusions: Iodine intakes may be insufficient for some women of childbearing age. Public health policies and programs should continue to recommend that all women who could become pregnant, or women who are pregnant or breastfeeding, take a daily multivitamin-mineral supplement containing iodine., (© Crown copyright 2021.)

Iodine is an essential mineral nutrient and an integral component of thyroid hormones. Iodine deficiency is typically associated with goiter, but can have more serious health implications. Adequate iodine status is important for normal brain development. Iodine deficiency in utero or in early life can cause severe neurological and cognitive impairment. Over the last three decades, global efforts have reduced the prevalence of iodine deficiency disorders (IDD) in many areas of the world with implementation of nutrition policies and programs such as "salt" iodization. However, in a number of areas iodine deficiency is still widespread. Iodine deficiency in remote regions with high poverty will be more difficult to eradicate. Efforts to eliminate IDD in affected areas and sustaining successful iodine programs will be a priority given the substantial public health and economic benefits. A key component will be periodic monitoring of population iodine status to ensure sufficient intakes and the absence of excessive intakes. Median urinary iodine concentration (UIC), a validated biomarker for assessing population iodine status, will facilitate monitoring. Research validating "usual" UIC for use in combination with the Estimated Average Requirement cut-point method will expand its utility and allow accurate determination of the prevalence of inadequate intakes in populations. Further research on the development of biomarkers for assessment of individual iodine status for routine patient care will be important., (Copyright © 2021 Elsevier Inc. All rights reserved.)