NZ children's iodine status still far from ideal: Otago research

The mandatory use of iodised salt in commercial bread since 2009 has improved New Zealand children’s iodine status but many may remain mildly deficient in this essential nutrient, new University of Otago research suggests.

Between November 2010 and February 2011, Department of Human Nutrition researchers measured biochemical markers of iodine status in 147 primary students from 18 randomly selected Dunedin and Wellington schools. The children were aged between 8 and 10.

The study findings are newly published in the British Journal of Nutrition.

The researchers found that the children’s median level of a short-term marker, urinary iodine concentration (UIC), was almost double that found in a 2002 study. It now fell just within the range for adequate iodine status.

However, the median level of thyroglobulin (Tg) concentration in the children’s blood was still in a range indicating mild iodine deficiency. Tg is a protein produced by the thyroid gland and has been proposed as a longer-term marker for iodine status.

Study lead author Dr Sheila Skeaff says that while it is pleasing that the research indicates that mandatory fortification of bread has had a positive impact in combating inadequate iodine status in children, room for improvement remains.

“The raised Tg levels we found suggest that some New Zealand children may still have enlarged thyroids because they are not getting enough iodine,” Dr Skeaff says.

In a study published in 2009, Dr Skeaff and colleagues revealed that correcting mild iodine deficiency led to small but significant improvements in children’s performance in cognitive tests.

“There are a number of steps parents can take to increase their children’s iodine intake. For example, if salt is used in preparing meals or at the table it should always be iodised. Dairy products, eggs, fish and other seafood are also good sources of iodine,” she says.

Dr Skeaff says it is important that children who eat little or no commercial bread products, which are now the main source of dietary iodine, get a sufficient intake from elsewhere.

“Our results also suggest that fortifying other staple foods needs to be considered if we want to ensure that New Zealand children have good iodine status,” she says.