Iodine status in pre-school children prior to mandatory iodine fortification in Australia

Food sources of iodine in schoolchildren and relationship with 24-h urinary iodine excretion in Victoria, Australia

Dietary recalls have been used previously to identify food sources of iodine in Australian schoolchildren. Dietary assessment can provide information on the relative contributions of individual food groups which can be related to a robust objective measure of daily intake (24-h urinary iodine excretion (UIE)). In Australia, the government has mandated the use of iodised salt in breadmaking to address iodine deficiency. The aim of this study was to determine the dietary intake and food sources of iodine to assess their contribution to iodine excretion (UIE) in a sample of Australian schoolchildren. In 2011-2013, UIE was assessed using a single 24-h urine sample and dietary intake was assessed using one 24-h dietary recall in a convenience sample of primary schoolchildren from schools in Victoria, Australia. Of the 454 children with a valid recall and urine sample, 55 % were male (average age 10·1 (1·3 (sd) years). Mean UIE and dietary iodine intake were 108 (sd 54) and 172 (sd 74) μg/d, respectively. Dietary assessment indicated that bread and milk were the main food sources of iodine, contributing 27 and 25 %, respectively, to dietary iodine. Milk but not bread intake was positively associated with UIE. Multiple regression (adjusted for school cluster, age and sex) indicated that for every 100 g increase in milk consumption, there was a 3 μg/d increase in UIE (β = 4·0 (se 0·9), P < 0·001). In conclusion, both bread and milk were important contributors to dietary iodine intake; however, consumption of bread was not associated with daily iodine excretion in this group of Australian schoolchildren.

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

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.

Iodine Intakes of Victorian Schoolchildren Measured Using 24-h Urinary Iodine Excretion

Mandatory fortification of bread with iodized salt was introduced in Australia in 2009, and studies using spot urine collections conducted post fortification indicate that Australian schoolchildren are now replete. However an accurate estimate of daily iodine intake utilizing 24-h urinary iodine excretion (UIE μg/day) has not been reported and compared to the estimated average requirement (EAR). This study aimed to assess daily total iodine intake and status of a sample of primary schoolchildren using 24-h urine samples. Victorian primary school children provided 24-h urine samples between 2011 and 2013, from which urinary iodine concentration (UIC, μg/L) and total iodine excretion (UIE, μg/day) as an estimate of intake was determined. Valid 24-h urine samples were provided by 650 children, mean (SD) age 9.3 (1.8) years (n = 359 boys). The mean UIE of 4–8 and 9–13 year olds was 94 (48) and 111 (57) μg/24-h, respectively, with 29% and 26% having a UIE below the age-specific EAR. The median (IQR) UIC was 124 (83,172) μg/L, with 36% of participants having a UIC < 100 μg/L. This convenience sample of Victorian schoolchildren were found to be iodine replete, based on UIC and estimated iodine intakes derived from 24-h urine collections, confirming the findings of the Australian Health Survey.

Vitamin D status and its predictors among pre-school children in Adelaide

AIM

To assess vitamin D status and its predictors in a representative population sample of pre-school children in Adelaide (latitude of 35°S).

METHODS

Cross-sectional survey of children aged between 1 and 5 years from areas of low, medium and high socio-economic status as identified from the 2001 Census data, Australian Bureau of Statistics. Children were recruited between September 2005 and July 2007 using a door knocking protocol based on a stratified sampling method to obtain a representative sample of this age group. Serum 25-hydroxyvitamin D (25(OH)D) was determined using a radio-immunoassay kit. Vitamin D deficiency was defined as serum 25(OH)D) <30 nmol/L and insufficiency defined as serum 25(OH)D ≥30 and <50 nmol/L according to the Institute of Medicine.

RESULTS

Fifty-two per cent of eligible children took part in the study. Mean (standard deviation) serum 25(OH)D was 73 (26) nmol/L (n = 221). The prevalence of vitamin D deficiency and insufficiency was 4% and 16%, respectively, with the prevalence being higher in winter (8% and 22%, respectively). Season of the year of blood collection and mother being born in Australia were significant predictors of serum 25(OH)D concentration, but age, sex, socio-economic status, BMI category or dietary supplement use were not related to vitamin D status.

CONCLUSIONS

Vitamin D status of this representative sample of pre-school children in Australia is adequate, and the prevalence of vitamin D deficiency is low based on the Institute of Medicine criteria.