Iodine intake and status of school-age girls in Ireland

Abstract

Purpose: Insufficient iodine intake can lead to a variety of preventable health and developmental outcomes. Consequently, continuous monitoring of a population's iodine adequacy is important. The aim of this study was to examine iodine intake and status in a nationally representative sample of school-age girls living in Ireland.

Methods: Analyses were based on 516 schoolgirls aged 5-18 years from the cross-sectional National Children's Food Survey II (2017-2018) and the National Teens' Food Survey II (2019-2020). Dietary data were collected using a four-day weighed food diary. Adequacy of iodine intake and the contribution of food categories to overall dietary iodine intake was assessed. Urinary iodine concentration (UIC) was measured using a spot urine sample using the Sandell-Kolthoff reaction by a modified microplate method.

Results: Median iodine intake was 94.8 µg/d (IQR 54.9-155.5 µg/d), with 40% of girls having intakes below the estimated average requirement (EAR). The median UIC was 87.8 µg/L, with younger girls having a significantly higher UIC compared to older girls (104.4 µg/L - 77.0 µg/L respectively; p < 0.001). The main dietary source was milk, contributing to over 50% of iodine intake, with non-consumers of milk having significantly lower dietary and urinary iodine levels compared to high consumers (p < 0.001).

Conclusion: This study suggests that school aged girls living in Ireland have mild iodine deficiency and given the concerns associated with such deficiencies and their potential public health implications, it is essential that iodine status in other population groups in Ireland is ascertained. The need for targeted public health strategies to eradicate iodine deficiency may be warranted.

Keywords: Children; Females; Iodine; Ireland; Teenagers.

Fig. 1

The relationship between quartiles of milk consumption with dietary iodine intake (µg/d) and urinary iodine status (µg/L) Milk intake used to calculate consumption groups refers to consumption of whole, semi-skimmed and skimmed milks; non-consumers recorded no consumption of milk (0 g/d), low consumers (2–87 g/d), medium consumers (88–192 g/d) and high consumers (193–845 g/d). Data presented as adjusted means derived from a covariate-adjusted general linear model. Covariates included: age, household location, education level of parent/guardian, social class, and underreporting. ^a,^b,^c Mean values with different lower case superscript letters were significantly different. Dietary iodine p < 0.001, n²p = 0.238; Urinary iodine p < 0.001, n²p = 0.094