The influence of mandatory iodine fortification on the iodine status of Australian school children residing in an iodine sufficient region.

Background And Objectives: To counter emerging iodine deficiency mandatory iodine fortification of bread was introduced throughout Australia in 2009. This study investigated the impact of iodine fortification on the iodine status of school aged children living in the iodine replete state of Queensland, and investigated which foods had greatest influence on overall iodine status.

Methods And Study Design: A convenience sample of 30 children aged 8.0-10.9 years living in south east Queensland, Australia, provided spot morning and afternoon urine samples on two consecutive days. Iodine status was categorised by the World Health Organization criterion. Semiquantitative food questionnaires (FFQ) completed by carers were used to investigate which foods were having the greatest influence on UIC. Analysis of variance was used to reduce the within person variation observed in urinary iodine concentrations (UIC) and the data were log transformed before statistical analysis.

Results: Adjusted median UIC was 144 ug/L (IQR 120-210 ug/L) indicating iodine sufficient status. No samples were above the cut off for excessive UIC. Bread was the only statistically significant contributor to UIC (standardized β=0.37, p=0.04) with 14% of variation in UIC explained by bread consumption. UIC increased by 8.7% for each additional serve of bread.

Conclusions: Iodine fortification of bread has increased the iodine status of school aged children in this Queensland cohort. Despite the small sample size in this study, improvements in methodology allowed its findings to be comparable to other, larger surveys.