Letters
Metabolic diseases Women's health
Volume 193 - Issue 5

Iodine deficiency in Australia: is iodine supplementation for pregnant and lactating women warranted?

Authors:  Shao J Zhou, Sheila A Skeaff, Philip Ryan and Maria Makrides

Med J Aust 2010; 193 (5): 309-311. || doi: 10.5694/j.1326-5377.2010.tb03921.x
Published online: 6 September 2010
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To the Editor: We disagree with the opinion expressed by Gallego and colleagues that Australian “women planning a pregnancy and pregnant and lactating women should be advised to take an iodine supplement”,1 and offer two reasons to support our view.

First, the data suggesting mild iodine deficiency in Australian women were collected from opportunistic samples of women not representative of the population at large and were obtained before the introduction of mandatory iodine fortification of bread in October 2009. We believe that recommending iodine supplementation in pregnancy without evaluating the effect of mandatory iodine fortification on iodine intake and status of pregnant women in Australia is premature.2 This is supported by a recent report, developed by the Dietitians Association of Australia on behalf of the National Health and Medical Research Council (NHMRC).3 The report clearly shows that the recommended iodine intake for pregnant women (recommended dietary allowance, 220 μg/day) is achievable from foods alone, together with iodine fortification of bread.

Second, there are no randomised controlled trials (RCTs) that have examined the effect of iodine supplementation of pregnant women from regions of mild iodine deficiency (as in Australia) on neurodevelopment of the offspring or any other clinical outcomes. Gallego et al state that “iodine-containing supplements consistently benefit the iodine and thyroid status of both mother and newborn”, citing a review of iodine supplementation of pregnant women from populations with mild-to-moderate iodine deficiency.4 In fact, none of the six RCTs included in that review showed a clear effect of supplementation on maternal and newborn thyroid hormone concentrations, which suggests that the maternal thyroid is able to adapt to meet the increased thyroid hormone requirements of pregnancy in areas of mild-to-moderate iodine deficiency.5 Furthermore, Gallego et al cite no evidence to support their statement “Even subclinical hypothyroidism in the mother, occurring as a consequence of iodine deficiency, can cause irreversible brain damage in the fetus . . .”.

In our view, major public health recommendations advising routine iodine supplementation for women planning a pregnancy, as well as pregnant and lactating women, should await the results of current RCTs6-8 examining the effect of maternal iodine supplementation on longer-term maternal health and neurodevelopmental outcome of children in regions with mild-to-moderate iodine deficiency, including Australia and New Zealand.

Authors

  • Shao J Zhou1
  • Sheila A Skeaff2
  • Philip Ryan3
  • Maria Makrides1
  • 1. Child Nutrition Research Centre, Women’s and Children’s Health Research Institute, University of Adelaide, Adelaide, SA.
  • 2. Department of Human Nutrition, University of Otago, Dunedin, New Zealand.
  • 3. Discipline of Public Health, University of Adelaide, Adelaide, SA.

Correspondence: maria.makrides@health.sa.gov.au

Competing interests

We are chief investigators of the NHMRC-funded multicentre RCT, which investigates the effect of iodine supplementation in pregnancy on neurodevelopment of children and general health and wellbeing of mothers. The supplements used in the trial are manufactured and donated to the trial by Blackmores.

References

View this article on Wiley Online Library