Mild iodine deficiency in a sample of New Zealand schoolchildren

Abstract

Objective: To assess the iodine status of New Zealand schoolchildren.

Design: A proportionate to population size school-based cluster survey was used to randomly select children from two cities. The indicators used to assess iodine status were urinary iodine, as determined in a casual urine sample, and thyroid volume, as measured by ultrasonography. A qualitative food frequency questionnaire designed to ascertain frequency of consumption over the previous 3 months of foods or food groups that are good sources of dietary iodine, including iodized salt, was administered to each child.

Setting: Dunedin and Wellington, New Zealand.

Participants: Three-hundred children aged 8-10 y from 30 schools.

Results: The median urinary iodine concentration of the children was 6.6 micro g/dl (interquartile range, 4.5-9.1). The percentage of children who had urinary iodine levels less than 5 micro g/dl was 31.4 (95% confidence interval (CI), 24.2-38.6). Comparison of thyroid volume with 2001 World Health Organization age/sex-specific and age/BSA-specific cut-off values resulted in a goitre prevalence of 11.3% (95% CI, 7.6-15.1) and 12.0% (95% CI, 7.9-16.1), respectively. Almost 30% of the children's caregivers did not use iodized salt in cooking and 51% of the children did not use iodized salt at the table.

Conclusions: Mild iodine deficiency was found in this sample of children. Iodized table salt may no longer be making a significant contribution to the iodine intakes of New Zealand children.