Unless you were a regular at the sushi bar or ate fish twice a week it used to be hard to get enough iodine in your diet – but there are signs that putting iodised salt in our bread has made this easier. Nearly four years ago concerns about iodine deficiency led to bread being fortified with iodised salt. Measures of iodine concentrations in the urine of school children in Tasmania show that iodine intake is higher now than before fortification began.
But we’re not out of the woods yet – there are also signs that pregnant women may not get enough iodine to ensure the optimal brain development of their unborn babies, says Associate Professor Karen Charlton of Wollongong University’s School of Health Sciences. Research by Charlton and her team suggests that many pregnant women may be low in this mineral which is essential for an unborn baby’s developing brain.
While adults need 150 mcg of iodine daily, the need for this mineral jumps by 50 per cent during pregnancy and breastfeeding - and that’s more than a few slices of bread with iodised salt can deliver. But although the National Health and Medical Research Council recommends iodine supplements for women who are pregnant or planning to be, 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," says Charlton. “But new research has linked a low iodine intake in pregnancy with a reduced IQ in children.”
One 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 to 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 in 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,” Charlton says.
Most adults should be able to get enough iodine with three slices of bread (unless it’s organic bread which isn’t required to have iodised salt) and two to three serves of dairy food daily, a couple of serves of fish or seafood weekly and sushi now and again, 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 in pregnancy.
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 which once boosted the iodine content of our dairy food, the fact that we now eat so much processed food which uses non-iodised salt and that we tend to use non-iodised salt at home.
If you’re pregnant or breastfeeding Karen Charlton suggests a multivitamin containing 150mcg of iodine – although women with a thyroid problem should talk to their doctor because too much iodine can exacerbate some thyroid conditions.
Can a healthier iodine intake in childhood make up for a shortfall in the womb?
“No - most brain development occurs during pregnancy,” explains 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 100mcg of iodine.”