26 May 2008
Concerns about a resurgence of iodine deficiency among mothers and children prompted a one-day forum in Canberra under the auspices of the Australian Academy of Science, International Life Sciences Institute Australia and the Nutrition Society of Australia. Although there were differing views as to the most effective actions to avoid iodine deficiency in Australia, there was almost unanimous agreement that there was cause for concern and that steps must be taken to avoid a serious situation developing.
Officially, Australia is now an iodine-deficient country based on studies of urinary excretion.1 The seriousness of the issue is reflected by the recent release of a proposal by Food Standards Australia New Zealand2 to extend the New Zealand-only standard, mandating the replacement of salt with iodised salt in bread to include Australia. Universal salt iodisation (USI) is recommended by the International Council for the Control of Iodine Deficiency – the expert international body – and WHO's key strategy to eliminate iodine deficiency disorders.
After the opening of the forum by the Hon Richard Colbeck, the Shadow Parliamentary Secretary for Health, Professor Cres Eastman described the features of iodine deficiency disorders and the intakes necessary to avoid signs of deficiency. Professor Eastman emphasised that even mild iodine deficiency would result in a reduction in average IQ and fewer gifted individuals. He noted studies from NSW and Victoria confirming that iodine deficiency is prevalent in more than 50% of pregnant women living in these states. Where USI has not been implemented, WHO recommends iodine supplements for vulnerable groups.
Dr Mu Li summarised recent studies on the iodine status of mainland Australian school children, showing that about 50% are classified as mildly or moderate iodine deficient. Among that group, 14% of children in NSW and 19% in Victoria (20% in Tasmania from 2001 data) are classed as moderately iodine deficient.
Professor Caryl Nowson described strategies for monitoring and education of the population, highlighting the need for government-funded ongoing systematic monitoring of different population groups in order to confirm the effectiveness of any iodine intervention strategy.
Dr Sheila Skeaff described the situation in New Zealand, concluding that fortification was imperative to increase iodine intakes in vulnerable groups. She emphasised that women planning a pregnancy, or pregnant and lactating women, must take an iodine supplement and that weaning foods be fortified to avoid iodine deficiency in infants and toddlers.
Ms Judy Seal described Tasmania's iodine supplementation program, begun in 2001, as in interim measure ahead of a national program. The use of iodised salt in bread and monitoring of iodine status has seen a small but significant increase in the iodine status of most Tasmanians. The status of pregnant women, however, remained inadequate.
Dr Dorothy Mackerras described the current regulatory situation in Australia and New Zealand and described mathematical models to increase population intakes so that the proportion with inadequate intakes and the proportion exceeding the upper level were minimised. She noted that, as the range of fortified foods increases, the concentration of iodine in salt has to be reduced to achieve the same result. Mandating iodised salt in bread alone (at 45 milligram iodine per kilogram salt) increases intakes in children aged 2 to 3 years such that less than 1% would have an inadequate intake and only 6% would have intake above the upper level. This approach also reduces the proportion of adult women with inadequate intakes from 59% to 9%. Owing to the higher requirements during pregnancy and lactation, most women in this life-stage would have inadequate intakes, although there is an overall increase of nearly 50 micrograms per day. Similar increases in iodine intake would be achieved across the different population groups by mandating USI using a concentration of 15 milligram iodine per kilogram salt. However USI would be more costly and impact imported foods. In all models, whether bread alone, USI or other possible scenarios, the upper level in young children is the limiting factor.Most, if not all of the experts, attending the meeting agreed that the upper level figure for 1 to 3 year-old children was an arbitrary figure and unlikely to be of pathophysiological significance.
Dr Stephen Goodall summarised modelling of the costs of iodine fortification of bread, demonstrating that mandatory fortification was the most cost-effective option.
A food industry perspective was presented by Ms Fiona Fleming from George Weston Foods. She emphasised that the most vulnerable groups – pregnant and lactating women – were not effectively targeted by mandatory fortification of bread with iodised salt. She wanted a commitment to urinary iodine monitoring program to avoid the situation that occurred with mandatory thiamine fortification. The food industry prefers voluntary use of iodised salt in food manufacture, based on developing a Memorandum of Understanding.
The final speaker was Dr Geoffrey Annison from the Australian Food and Grocery Council. His view was that there not sufficient evidence to document effective targeting using bread. He expressed concern that there were no initiatives to support the proposals with education and little exploration of alternative approaches.
Professor Jennie Brand-Miller
Chair, National Committee for Nutrition
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