Iodine status in Melbourne adults in the early 1990s and 2007-08

Iodine Status among Somali Immigrants in Norway

We lack knowledge about iodine status in the Norwegian population in general, and particularly among immigrants. We aimed to estimate the iodine status and potentially associated factors in a Somali population in Norway. Somali men and women aged 20–73, who were living in one district in Oslo, were recruited between December 2015 and October 2016. Twenty-four-hour urine was collected from 169 participants (91 females and 78 males). Iodine was analysed using the Sandell–Kolthoff reaction on microplates and colorimetric measurement. Information about diet was collected using a short food frequency questionnaire. Iodine intake was calculated from the 24-h iodine excretion. The mean urine volume over 24-h was 1.93 liters (min–max: 0.55–4.0) and the urinary iodine concentration (UIC) varied from 13 to 263 µg/L with a median value of 62.5 µg/L indicating a population with mild iodine deficiency. The median daily iodine intake for the study population was estimated to be 124 μg/day. Mean serum thyroid-stimulating hormone, thyroxine (T4) and triiodothyronine (T3) was 2.1 (SD 1.1) mU/L, 15.0 (SD 2.1) pmol/L, and 5.1 (SD 0.6) pmol/L, respectively. No food groups were associated with iodine intake and neither was gender, age, education level nor length of residence in Norway. In conclusion, this study showed that iodine intake was low, and a considerable proportion of the Somali population studied had sub-optimal iodine status. Monitoring of iodine status should be prioritised and measures to ensure adequate iodine intake, particularly among vulnerable groups initiated.

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.

Development and validation of an iodine-specific FFQ to estimate iodine intake in Australian pregnant women

Adequate iodine is important during pregnancy to ensure optimal growth and development of the offspring. We validated an iodine-specific FFQ (I-FFQ) for use in Australian pregnant women. A forty-four-item I-FFQ was developed to assess iodine intake from food and was administered to 122 pregnant women at 28 weeks gestation. Iodine supplement use was captured separately at 28 weeks gestation. Correlation between iodine intake from food estimated using the I-FFQ and a 4 d weighed food record as well as correlation between total iodine intake and 24 h urinary iodine excretion (UIE), 24 h urinary iodine concentration (UIC), spot UIC and thyroid function were assessed at 28 weeks gestation. A moderate correlation between the two dietary methods was shown (r 0·349, P< 0·001), and it was strengthened with the addition of iodine supplements (r 0·876, P<0·001). There was a fair agreement (k= 0·28, P<0·001) between the two dietary measures in the classification of women as receiving adequate (≥160 μg/d) or inadequate (<160 μg/d) iodine intake from food, but the limits of agreement from the Bland-Altman plot were large. Total iodine intake was associated with 24 h UIE (β = 0·488, P<0·001) but not with spot UIC. Iodine intake from food using the I-FFQ was assessed at study entry (<20 weeks gestation) in addition to 28 weeks gestation, and there was a strong correlation in iodine intake at the two time points (r 0·622, P<0·001), which indicated good reproducibility. In conclusion, the I-FFQ provides a valid tool for estimating iodine intake in pregnant women and can be used to screen women who are at risk of inadequate intake.

Improvement in iodine status of pregnant Australian women 3 years after introduction of a mandatory iodine fortification programme

INTRODUCTION

In order to address population-level mild iodine deficiency in Australia, a mandatory iodine fortification programme of salt used in bread was introduced in late 2009.

METHODS

A before-after study was conducted to assess changes in median urinary iodine concentration (MUIC) measurements, according to supplement use, in convenience samples of pregnant women attending a public antenatal clinic in a regional area of New South Wales, Australia in 2008 (n=139), 2011 (n=147) and 2012 (n=114). Knowledge and practices related to iodine nutrition were investigated in 2012, using self-administered questionnaires.

RESULTS

The mild iodine deficiency confirmed pre-fortification (MUIC (IQR)=87.5 (62-123.5; n=110)) has steadily improved to 145.5 μg/L (91-252) in 2011 (n=106) and 166 (97-237) in 2012 (n=95) (sufficiency ≥ 150 μg/L). However, only women taking supplements containing iodine had MUIC indicative of sufficiency in both years surveyed post fortification (2011: 178 μg/L vs. 109 μg/L, P<0.001; 2012: 202 μg/L vs. 124 μg/L, P<0.05). Despite bread being the vehicle for iodine fortification, dairy foods remained major contributors to total iodine intake (58%). Overall knowledge regarding health implications of iodine deficiency was poor.

CONCLUSIONS

Iodine status of women has improved since the introduction of mandatory iodine fortification; however supplementation is indicated during pregnancy.