Unless you were a regular at the sushi bar or ate fish at least twice a week, it used to be hard to get enough iodine in your diet, but putting iodised salt in our bread has made it easier. Almost four years after concerns about iodine deficiency led to bread being fortified with iodised salt, measures of iodine concentrations in Tasmanian school children show that intake is higher than before fortification began.
But we're not out of the woods yet. According to associate professor Karen Charlton, of the University of Wollongong's school of health sciences, there's evidence that pregnant women may not be getting enough iodine to ensure optimal brain development of their unborn babies.
While adults need 150 micrograms of iodine daily, the need for the mineral jumps by 50 per cent during pregnancy and breastfeeding - that's more than just a few slices of bread with iodised salt. The National Health and Medical Research Council recommends iodine supplements for women who are pregnant or planning to be, but Charlton says the message isn't loud enough.
"In surveys we've done in the Illawarra region, about 40 per cent of women attending public antenatal clinics said they don't take iodine supplements. Women aren't aware how important iodine is in pregnancy and my feeling is that many women aren't given advice to take a supplement,'' Charlton says.
"But new research has linked a low iodine intake in pregnancy with a reduced IQ in children."
A UK study published in the medical journal The Lancet in May reported that children of women with a mild to moderate iodine deficiency in pregnancy had lower scores for verbal IQ, reading accuracy and reading comprehension, compared with children born to women with adequate iodine intakes.
A study from Tasmania's Menzies Research Institute has also attributed better scores on the NAPLAN school test in nine-year-olds to differences in iodine intakes of their mothers during pregnancy.
"There are many factors affecting a child's intellectual development, including childhood experiences and the parents' education level - but these studies controlled for other factors and still found an impressive association with iodine intake in pregnancy."
Most adults should be able to get enough iodine with three slices of bread and two to three serves of dairy food daily, a couple of serves of fish or seafood weekly, and the occasional sushi meal, Charlton says. But this may not be enough for pregnant women - especially those who don't eat much bread or are wary of eating fish.
How did we get to be low on iodine to begin with? There are a few reasons - low iodine levels in soil; less use of iodine-based cleaning products in the dairy industry that once boosted the iodine content of our dairy food; the fact we now eat so much processed food, which uses non-iodised salt; and the use of non-iodised salt at home.
If you're pregnant or breastfeeding, Karen Charlton suggests a multivitamin containing 150 micrograms of iodine - although women with thyroid problems should talk to their doctor, because iodine can exacerbate some thyroid conditions.
Can a healthier iodine intake in childhood make up for a shortfall that occurred while in utero?
"No - most brain development occurs during pregnancy," said Professor Cres Eastman, Asia Pacific regional co-ordinator for the International Council for Control of Iodine Deficiency Disorders.
"But an adequate iodine intake is still important in childhood, and children who don't drink milk or eat bread - foods that are often the main source of iodine in childhood - need a daily supplement of 100 micrograms of iodine."