The re-emergence of iodine deficiency (ID) in Australia, particularly in the south-eastern states of New South Wales, Victoria and Tasmania, in the late 1990s/early 2000s resulted in two national public health responses. The first, involving fortification of commercially baked bread with iodised salt, was begun in Tasmania in 2001 and became mandatory across Australia and New Zealand in 2009. This initiative has seen the general population in Tasmania return to a status of iodine sufficiency.
Recognition that the increased iodine requirements of pregnant and breastfeeding women would be difficult to attain by bread fortification alone, the second initiative was introduced in 2010 with the National Health and Medical Research Council (NHMRC) recommending daily iodine supplementation for women planning pregnancy, and for the duration of gestation and lactation. Adequacy is vital during pregnancy, as even mild ID has been shown by our team and others to be associated with deficits in neuro-cognitive development manifesting as persistent poorer educational outcomes and lower IQ.
While supplementation improves the iodine status of pregnant and breastfeeding women, studies conducted in different Australian regions indicate that the optimal level and timing of supplementation requires further investigation. Our research suggests that non-pregnant/non-breastfeeding women of child-bearing age in Tasmania remain iodine deficient despite bread fortification and as such may have insufficient thyroid stores prior to conception to maintain iodine sufficiency throughout gestation, even if they begin supplementing once pregnant. Only women who began supplementation prior to conception and continued throughout pregnancy, at the recommended dose, were able to maintain an iodine status within current World Health Organization recommendations. Other Australian research suggests that iodine supplementation may not be warranted and even detrimental in regions without ID.
Given the potential for vast regional, and indeed individual, variation in the underlying iodine status of women in Australia, a national survey of women of reproductive age and of pregnant and breastfeeding women is warranted to inform the appropriateness of the current NHMRC supplementation recommendations. Development of methods to determine individual iodine status, in addition to existing reliance on epidemiological-based population assessment, is also merited.