Iodine status in Norwegian preschool children and associations with dietary iodine sources: the FINS-KIDS study

Abstract

Purpose: Iodine is an essential trace element necessary for thyroid hormone synthesis. Iodine deficiency is a continuing public health problem despite international efforts to eliminate it. Studies on iodine status in preschoolers are scarce. Thus, the aims of the current study were to determine the iodine status and to investigate possible associations between urinary iodine concentration (UIC) and estimated 24 h iodine extraction (UIE) and iodine-rich foods.

Methods: Data are cross-sectional baseline data, obtained from the two-armed randomized controlled dietary trial "Fish Intervention Studies-KIDS" (FINS-KIDS) conducted in Bergen, Norway. UIC was determined by inductively coupled plasma-mass spectrometry in spot urine samples. Inadequate UIC was defined as median < 100 µg/L, and low estimated 24 h UIE as < 65 µg/day. Habitual dietary intake was assessed by a short food frequency questionnaire. Logistic regression models were used to investigate possible associations between UIC and estimated 24 h UIE and iodine-rich dietary sources including seafood, dairy products and eggs. Iodine/creatinine ratio (I/Cr) was also estimated.

Results: Urinary spot samples were obtained from 220 children. The median (interquartile range) UIC and estimated 24 h UIE was 132 (96) µg/L, and 65 (55) µg/day, respectively. The majority of children had an estimated I/Cr ratio within 100-199 µg/g. Intake of sweet milk < 2 times/day versus ≥ 2 times/day was associated with UIC < 100 µg/L (OR 2.17, 95% CI 1.07-4.38, p = 0.031). Intake of dairy products (OR 3.59, 95% CI 1.13-11.43, p = 0.031) and sweet milk (OR 2.77, 95% CI 1.37-5.61, p = 0.005) < 2 times/day versus ≥ 2 times day was associated with estimated 24 h UIE < 65 µg/day.

Conclusions: The preschoolers had adequate iodine status. Low intake of sweet milk and dairy products were associated with low iodine status.

Keywords: Creatinine; Fish; Iodine; Milk; Preschoolers; Urinary iodine concentration.

Fig. 1

Distribution of urinary iodine concentrations among the children (N = 220). Presented according to World Health Organization (WHO)/United Nations Children’s Fund (UNICEF)/International Council for Control of Iodine Deficiency Disorders (ICCIDD) criteria on iodine nutrition in populations (based on surveys in school-aged children ≥ 6 years old)

Fig. 2

Distribution of urinary iodine concentration and estimated iodine/creatinine ratio among the children and how they are classified in relation to one another (N = 220). Each dot represents one child