IHN Database

Iodine deficiency common in Australia

IHN logo ST. LEONARDS, NSW, AUSTRALIA. Iodine deficiency during pregnancy can adversely affect the thyroid glands of both the mother and baby. It can also result in lowered intelligence and is considered to be the most common cause of preventable intellectual disability. Inadequate iodine intakes have long been thought to be a problem only in developing countries, but a recent study in the United States showed that almost 12 per cent of the American population is iodine deficient and that the average iodine intake has dropped by 50 per cent over the last 15 years. The recommended daily intake of iodine is 100 micrograms for the general population and 150-200 micrograms for pregnant and breastfeeding women. About 90 per cent of ingested iodine is excreted in the urine so iodine status can be accurately assessed by a simple urine analysis. A urinary iodine concentration between 51 and 100 micrograms/L indicates a mild deficiency, a concentration between 26 and 50 micrograms/L corresponds to a moderate deficiency, and a concentration below 25 micrograms/L indicates a severe deficiency.

Medical researchers at the Royal North Shore Hospital now report the first disturbing evidence that iodine deficiency may be widespread in Australia. Their investigation involved 81 pregnant women, 26 of whom were also checked three months after giving birth, 135 diabetes patients, and 19 volunteers. Analyses of urine samples from all 235 participants showed that 19.8 per cent of the pregnant women, 34.1 per cent of the diabetics, and 26.3 per cent of the volunteers had a moderate to severe iodine deficiency. As a matter of fact, only 40 per cent of the 235 participants had a normal iodine status, e.g. a urine concentration above 100 micrograms/L. The researchers suggest that dietary sources of iodine in Australia may no longer be sufficient partly because the use of iodised table salt has declined significantly in recent years and partly because manufacturers of processed foods use only non-iodised salt in their products. They also point out that milk used to contain significant amounts of iodine because iodine-containing solutions were used to clean milking equipment and containers. These solutions, however, have now been replaced by more "modern" chemicals thereby eliminating an important source of iodine. The researchers urge further larger scale studies to better define the problem.

Dr. Creswell J. Eastman of the University of Sydney supports the call for further investigations and perhaps mandatory iodisation of all salt. As an immediate precaution he recommends iodine supplements for all pregnant women from the time of conception until weaning of the infant. NOTE: Well-formulated multivitamin tablets usually contain 150 micrograms of iodine per daily dose.
Gunton, Jenny E., et al. Iodine deficiency in ambulatory participants at a Sydney teaching hospital: is Australia truly iodine replete? Medical Journal of Australia, Vol. 171, November 1, 1999, pp. 467-70
Eastman, Creswell J. Where has all our iodine gone? Medical Journal of Australia, Vol. 171, November 1, 1999, pp. 455-56 (editorial)

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