Iodine Status of Canadian Children, Adolescents, and Women of Childbearing Age

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 mu g/L, the lower cutoff for adequate intakes. For women 20-39 y old, the median UIC of an unadjusted sample was 81 mu g/L (95% CI: 67, 95) and for the usual UIC was 108 mu g/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.