Volume 193 - Issue 5
Iodine deficiency in Australia: is iodine supplementation for pregnant and lactating women warranted?
Authors: Gisselle Gallego, Stephen Goodall and Creswell J Eastman
Med J Aust 2010; 193 (5): 309-311. || doi: 10.5694/j.1326-5377.2010.tb03922.x
Published online: 6 September 2010
Published online: 6 September 2010
In reply: While Zhou and colleagues disagree with our viewpoint that Australian “women planning a pregnancy and pregnant and lactating women should be advised to take an iodine supplement”,1 we note that they suggest any such recommendation should await the results of their planned randomised controlled trial (RCT) examining the effects of maternal iodine supplementation on maternal health and neurodevelopmental outcome of the offspring. They neglect to mention that the National Health and Medical Research Council (NHMRC) issued a public statement in January this year, with supporting evidence attached, stating that: “The NHMRC recommends that all women who are pregnant, breastfeeding or considering pregnancy take an iodine supplement of 150 μg each day”.2 Similar recommendations, based upon available scientific evidence, have been issued by the World Health Organization, International Council for Control of Iodine Deficiency Disorders, American Thyroid Association and American Endocrine Society.
We agree that there is a paucity of RCT evidence examining the effect of iodine supplementation of pregnant women living in mildly iodine-deficient areas, and this is regrettable. Given the overwhelming animal and human evidence that maternal iodine deficiency causes brain damage in the offspring of deficient mothers, we consider there are major ethical issues in conducting such trials where pregnant women would be deprived of iodine and their babies put at risk of brain damage.
Zhou and colleagues imply that mild-to-moderate iodine deficiency is not widely prevalent in Australia. This statement ignores the evidence from several clinical studies of pregnant women in New South Wales, Victoria and Tasmania, all showing that mild-to-moderate iodine deficiency is widespread in the majority of the Australian population. Analysis of the data in some of these studies shows between 20% and 40% of women tested are moderately to severely iodine deficient.3 Furthermore, food modelling studies by Food Standards Australia New Zealand (FSANZ) predict between 45% and 75% of Australian women will continue to be iodine deficient after the mandatory use of iodised salt in bread that commenced in October 2009.4
Finally, we disagree with their assertion that the recommended iodine intake for pregnant women can be achieved by the majority of women from foods alone, together with iodine fortification of bread. A trial of bread fortification in Tasmania showed this was not achievable.5 If this were achievable, it is questionable why Zhou and colleagues would even consider conducting an RCT of maternal iodine supplementation in pregnant women in Australia and NZ.
Competing interests
Gisselle Gallego and Stephen Goodall coauthored reports for FSANZ and the Department of Health and Ageing on the cost-effectiveness of iodine fortification of bread in Australia and NZ. Stephen Goodall is an FSANZ fellow. Creswell Eastman is the vice-chairman of the International Council for Control of Iodine Deficiency Disorders, which is supported by the Australian Government Overseas Aid Program and the Canadian International Development Agency. Creswell Eastman is patron of the Australian Thyroid Foundation, which has received support from Cerebos (manufacturer of Saxa salt) and Blackmores.
References
- Gallego G, Goodall S, Eastman CJ. Iodine deficiency in Australia: is iodine supplementation for pregnant and lactating women warranted? Med J Aust 2010; 192: 461-463. Ref1c
- National Health and Medical Research Council. Iodine supplementation for pregnant and breastfeeding women [public statement]. NHMRC, 2010. http://www.nhmrc.gov.au/_files_nhmrc/file/publications/synopses/new45_statement.pdf (accessed Aug 2010).
- Hamrosi MA, Wallace EM, Riley MD. Iodine status in pregnant women living in Melbourne differs by ethnic group. Asia Pac J Clin Nutr 2005; 14: 27-31. 0_i1095410
- Food Standards Australia New Zealand. Proposal P1003 Mandatory iodine fortification for Australia: assessment report. Canberra: FSANZ, 2008. http://www.foodstandards.gov.au/_srcfiles/P1003%20 Mandatory%20Iodine%20fortification%20Aust% 20AR%20FINAL.pdf (accessed Aug 2010).
- Seal JA, Doyle Z, Burgess JR, et al. Iodine status of Tasmanians following voluntary fortification of bread with iodine. Med J Aust 2007; 186: 69-71. 0_pgfId-2100832