Research from the University of Adelaide shows that iodized salt used in bread is not enough to provide healthy levels of iodine for pregnant women and their unborn children.
The study - led by researchers from the University’s Robinson Institute – has prompted calls for pregnant women to keep taking iodine supplements.
Iodine deficiency is recognized by the World Health Organization (WHO) as the most common preventable cause of brain damage in the world.
“Iodine is an essential element which is important for human brain development and thyroid function,” says one of the lead authors of the study, Associate Professor Vicki Clifton from the University’s Robinson Institute and the Lyell McEwin Hospital.
“In 2009, Australian bread producers began a mandatory program of iodine supplementation in bread to help provide a boost to iodine levels in the community. Our study was aimed at determining whether or not that was having a positive impact on iodine levels for pregnant women.”
In the study, almost 200 South Australian women were tested throughout their pregnancy and six months after giving birth.
“We found that South Australian women are mildly iodine deficient. Despite the inclusion of iodized salt in bread, women who were not taking an iodine supplement during pregnancy were still suffering from iodine deficiency,” Associate Professor Clifton says.
“Those women who were taking a supplement in addition to eating bread with iodized salt were receiving healthy levels of iodine, well within WHO guidelines.”
This is the latest study to follow on from the pioneering work of the University’s Emeritus Professor Basil Hetzel AC, who began researching iodine deficiency more than 50 years ago at the Queen Elizabeth Hospital, in collaboration with the Papua New Guinea Public Health Department.
Why iodised salt is necessary
Iodine helps prevent brain damage and mental impairment and is especially important for brain development in unborn babies. The wet New Zealand climate means iodine is not available in sufficient quantities in the plants and animals we eat. Fortifying bread with iodine:
helps increase the amount of iodine in New Zealanders’ diet
prevents iodine deficiency from becoming more serious in future.
Products that require iodised salt
You must use iodised salt in almost all bread and bread products. The standard defines the bread and bread products that must contain iodised salt.
There are some exceptions to the use of iodised salt, including:
salt on the surface of bread, for example rock salt
other ingredients containing salt that are added to bread
bread not intended for sale in New Zealand or Australia.
His work revealed very low urine iodine levels and high rates of goitre were associated with a form of brain damage called ‘cretinism’. Professor Hetzel showed that this brain damage could be prevented by correcting the severe iodine deficiency before pregnancy.
“There’s a lot of work going on around the world to ensure that pregnant women are receiving enough iodine for the healthy development of their unborn babies,” says Professor Hetzel, who is also a lead author on this current study.
“The message is simple: by taking iodine supplements, pregnant women will be able to prevent brain and organ development problems in their babies, and also maintain a healthy level of iodine for themselves.”
Professor Hetzel says Australia continues to be a world leader in this field, “but there is still very little public understanding about the dangers of iodine deficiency”.
Bread sold in Australia must contain iodised rather than ordinary salt from Friday (October 9, 2009).
Bakers are required to use only salt with the added essential nutrient, in a move by health officials to address the re-emergence of iodine deficiency in Australia.
“Iodine is particularly important for the normal development of a baby’s brain and nervous system,” said Dr Paul Brent, chief scientist for Food Standards Australia New Zealand (FSANZ).
“Not having enough iodine during pregnancy and early childhood can cause developmental delays and lead to reductions in mental performance ... this damage prior to 2-3 years of age is irreversible.”
Dr Brent said adults also needed iodine to ensure the healthy function of their thyroid gland, to help it produce hormones that regulate metabolism and body temperature.
Iodine is also found in fish, seafood, dairy products and eggs, and a constant dietary intake is required, Dr Brent said, as the human body did not store iodine in large amounts.
“Mandatory iodine fortification (of bread) is expected to reduce inadequate iodine intakes from 43 per cent to less than five per cent of the Australian population,” he said.
The results of this study were published in the Nutrition Journal.
Associate Professor Vicki Clifton
NHMRC Senior Research Fellow Robinson Institute
The University of Adelaide
Phone: +61 8 8133 2133
University of Adelaide