A lack of iodine may partly explain why Australian schoolchildren are being beaten in international tests by their counterparts in Korea, Singapore and Hong Kong, according to an expert on iodine deficiency.
Prime Minister Julia Gillard has set the goal of Australia's school system being in the world's top five by 2025.
International test results released in December placed Australia 27th in the world in year 4 reading, 22nd in science and 18th in maths.
Writing for Fairfax Media today, Cres Eastman, a professor of medicine at the University of Sydney and an internationally noted expert on iodine deficiency, says the top performing systems, including Singapore, Korea and Hong Kong, had diets that were rich in iodine because of salt iodisation and consumption of fish and seaweed.
In contrast, he said a national survey of schoolchildren in 2003-04 had confirmed the re-emergence of iodine deficiency here after an absence of almost half a century.
The main cause of the problem was that the dairy industry had stopped using iodine to sterilise milk containers, because it caused fluctuating levels - but this had been compounded by the reluctance of consumers to buy iodised salt for home use, and the fact that the local food industry made only limited use of it in food manufacturing.
Since 2009, Australian regulations have required iodised salt be used in all bread except organic bread.
The World Health Organisation has identified iodine deficiency as the ''commonest global cause of preventable loss of intellectual performance''. During pregnancy moderate to severe iodine deficiency can cause an irreversible loss of 10 to 15 IQ points in offspring. Health authorities recommend iodine supplements of 150 micrograms a day for pregnant or breast-feeding women.
Professor Eastman said iodine deficiency was not the only cause of Australian schoolchildren's poor performance but ''may well be a significant contributory factor''.