Home > National Committees

NATIONAL COMMITTEE FOR NUTRITION

Iodine deficiency
A document prepared by the National Committee for Nutrition

More than 50 countries around the world are iodine-deficient. Deficiency occurs when the soil is poor in iodine, causing a low concentration in the food supply and low dietary intakes. Historically, people living in Tasmania, the Australian Capital Territory, New South Wales (NSW), Victoria and New Zealand had low iodine intakes. Studies conducted over the last decade in NSW and Victoria, where approximately 60 per cent of the Australian population live, indicate the presence of mild-to-moderate iodine deficiency in all groups tested, however Western Australia and Queensland appear to have adequate intakes, whilst South Australia is borderline. Iodine deficiency appears to be an even greater problem in New Zealand. The current deficiency is not fully understood but may be related to the reduced use of iodine-based cleaning products in the dairy industry, leading to lower concentrations of iodine in milk and the decreased consumption of iodised salt.

Iodine is essential for the production of thyroid hormones and thyroid health throughout life. Thyroid hormones regulate body temperature and metabolic rate in adults and children. These hormones are also very important for the normal development of the brain and nervous system before birth, in babies, and young children. It is therefore particularly important that pregnant women, breast-feeding mothers and young children have an adequate dietary iodine intake. In children iodine deficiency can impair the development of the brain and nervous system, with the most crucial period being from foetal development to the third year of life. Iodine deficiency leads to poor school performance, reduced intellectual ability and impaired work capacity. The most damaging disorders induced by iodine deficiency are irreversible mental retardation

The World Health Organization (WHO) recommends iodisation of all salt as the main strategy for the control of global iodine deficiency. In May 2007, Food Standards Australia New Zealand (FSANZ) released a revised proposal for the mandatory fortification of salt with iodine for all salt used in bread manufacturing, with a salt iodisation range from 35 to 55 milligrams of iodine per kilogram of salt. This proposal is now at the final assessment stage. Further policy advice relating to this proposal is being sought by the Ministerial Council. The Australian health ministers are currently re-evaluating the evidence on the prevalence and severity of iodine deficiency in Australia. FSANZ's dietary intake estimates indicate that 88 per cent of Australians consume bread. Since 2001 the majority of bread manufacturers in Tasmania have voluntarily used iodised salt in the bread manufacturing and this has reduced the rate of iodine deficiency in children, but not in pregnant women.

It is unlikely that the mandatory use of iodised salt in bread manufacturing will deliver enough additional iodine to fully meet the needs of pregnant and breast-feeding women, whose requirements are substantially higher than the rest of the population; but it will make it more likely for women to enter pregnancy with adequate iodine stores, decreasing the risks of pregnancy affected by iodine deficiency.

Salt contributes to hypertension and there are efforts globally to encourage everyone to eat less salt. Therefore the substitution of iodised salt for salt in a widely eaten food is preferable to advising people to add iodised salt to their food. FSANZ are not proposing adding more salt to bread, just substituting the salt already used with iodised salt.

> Iodine deficiency – questions and answers