Iodine status of Tasmanians following voluntary fortification of bread with iodine

Abstract

Objective: To describe changes in the iodine status of Tasmanians following voluntary fortification of bread with iodine in October 2001. Design and setting: Post‐intervention, cross‐sectional urinary iodine surveys of Tasmanian schoolchildren aged 8–11 years were used to assess population iodine status. Participants were selected using a one‐stage cluster sampling method. The sampling frame comprised classes containing fourth‐grade children from all Tasmanian government, Catholic and independent schools. Results were compared with pre‐intervention survey results. Main outcome measures: Median urinary iodine concentration (UIC) and percentage of UIC < 50 μg/L ascertained from spot urine samples. Results: Median UIC was 75 μg/L in 1998, 72 μg/L in 2000, 105 μg/L in 2003, 109 μg/L in 2004 and 105 μg/L in 2005. Median UIC in post‐intervention years (2003–2005) was significantly higher than in pre‐intervention years. The percentage of UIC results < 50 μg/L was 16.9% in 1998, 18.7% in 2000, 10.1% in 2003, 10.0% in 2004 and 10.5% in 2005. Conclusion: Despite methodological differences between the pre‐ and post‐intervention surveys, switching to iodised salt in bread appears to have resulted in a significant improvement in iodine status in Tasmania. Given iodine deficiency has been identified in other parts of Australia and in New Zealand, mandatory iodine fortification of the food supply in both countries is worthy of consideration. As voluntary fortification relies on industry goodwill, mandating fortification could be expected to enhance population reach and give a greater guarantee of sustainability in Tasmania.

Iodine Intake and Thyroid Function in Pregnant Women in a Private Clinical Practice in Northwestern Sydney before Mandatory Fortification of Bread with Iodised Salt

“…The median urinary iodine level of 81  μ g/L was similar to the level we found in a pregnant population in Sydney approximately 10 years ago indicating that the situation has not improved despite publicity in the medical and lay press about iodine deficiency [7]. Similar reports of iodine deficiency have come from Victoria and Tasmania where the degree of iodine deficiency in pregnant women may be even worse than NSW [9, 11]. Extrapolating from the urinary iodine excretion to calculate daily intake [6], it is evident that these pregnant women are only taking, on average, a little more than half (132  μ g) the recommended daily intake (RDI for pregnancy of 250  μ g per day [12].…”

“…[3, 7–11]. None of these studies in pregnant women have examined thyroid function or thyroid volume so it is unknown if iodine deficiency documented in pregnant Australian women has any significant adverse effect on thyroid function.…”

The impact of iodine supplementation and bread fortification on urinary iodine concentrations in a mildly iodine deficient population of pregnant women in South Australia

“…There has been a significant improvement in the iodine status of Tasmanian schoolchildren from mildly iodine-deficient to borderline iodine-sufficient [14]. However, the iodine status of pregnant Tasmanian women showed a non-significant improvement rising from 76 to 81–86 μg/L, still in the mildly deficient range [15].…”

Estimating the impact of mandatory fortification of bread with iodine on pregnant and post-partum women

“…An intervention programme in the state of Tasmania took advantage of the permission in the Australian and New Zealand Food Standards Code allowing iodised salt to be used to manufacture food to establish an arrangement with the baking industry in that state. It is estimated that 80% of bread baked in Tasmania subsequently contained iodised salt 12. This intervention increased median urinary iodine concentration from 75 μg/l, in the mild deficiency range, to 105 μg/l which is at the lower end of the acceptable range 12.…”

“…It is estimated that 80% of bread baked in Tasmania subsequently contained iodised salt 12. This intervention increased median urinary iodine concentration from 75 μg/l, in the mild deficiency range, to 105 μg/l which is at the lower end of the acceptable range 12. During this time, a study of pregnant women attending a hospital antenatal clinic reported an increase of 10 μg/l in urinary iodine concentration, but these women were still iodine-deficient 13…”