Adequate iodine intake is required for the synthesis of thyroid hormones supporting development of the brain and central nervous system. However, excessive iodine intake can inhibit synthesis of thyroid hormones. Inadequate intakes of iodine is a problem globally, affecting people in low-, middle-, and high-income countries. Changes in the food supply, policies and regulations, as well as dietary habits over time can influence iodine status of the population, and thus routine evaluations should be performed to prevent deficiencies or excess intakes. Bertinato and colleagues performed an assessment in Canada and report their results in a paper published in the December 2021 issue of The Journal of Nutrition.
Data for this analysis were obtained using duplicate urinary spot samples collected one week apart from children (n=1875), adolescents (n=557), and women of childbearing age (n=567) participating in the Canadian Health Measures Survey. Urinary iodine and creatinine concentrations were determined, and those data were used to estimate usual urinary iodine concentrations and iodine intakes. Iodine status was assessed by comparing the median urinary iodine concentrations with reference ranges and by estimating the prevalence of inadequate or excess intakes.
Iodine intakes of male and female children (6-11 years), and adolescents (12-19 years) were above the cutoff for adequate intakes. Although the median values obtained for women was above the cutoff, it was well below the value necessary to support pregnancy and breastfeeding. The percentage of observations below the upper limit of intakes ranged from 91-100% for all of the sex-age groups studied. The authors concluded that iodine intake may not be sufficient for women of childbearing age, and that recommendations should be provided to this group to take a daily vitamin containing iodine.
In an editorial, Brough suggests that because the study by Bertinato and colleagues did not measure iodine levels in pregnant or breastfeeding women, and since the data suggest women had adequate intakes at a population level, it is likely that many pregnant and breastfeeding women are not consuming sufficient iodine. Because of the negative effects of insufficient iodine intake during pregnancy, Brough recommends continued monitoring of iodine status in children and vulnerable groups including pregnant and breastfeeding women. Brough also suggests a daily supplement containing 150 µg of iodine should be routinely consumed by all women well before conception.
References
Jesse Bertinato, Cunye Qiao, Mary R L’Abbé, Iodine Status of Canadian Children, Adolescents, and Women of Childbearing Age, The Journal of Nutrition, Volume 151, Issue 12, December 2021, Pages 3710–3717, https://doi.org/10.1093/jn/nxab268.
Louise Brough, Iodine Intake for Pregnant and Breastfeeding Women and Their Infants Remains a Global Concern, The Journal of Nutrition, Volume 151, Issue 12, December 2021, Pages 3604–3605, https://doi.org/10.1093/jn/nxab364.
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