Iodine status of pregnant women in South Australia after mandatory iodine fortification of bread and the recommendation for iodine supplementation.

Abstract

Mandatory iodine fortification of bread was introduced in 2009 in Australia in response to the reemergence of iodine deficiency. The aim of this study was to assess iodine intake, urinary iodine concentration (UIC) and their correlation in pregnant women (n=783) recruited from South Australia 2years following mandatory iodine fortification. Total iodine intake (food and supplements) and UIC were assessed at study entry (<20weeks') and at 28weeks' gestation. Mean (±SD) total iodine intake at study entry and 28weeks' gestation was 307±128μg/day and 300±127μg/day, respectively. Overall, 85.9% of women met the estimated average intake (≥160μg/day) for iodine in pregnancy, but only 44.5% met the estimated average intake from food alone. The main food sources of iodine were dairy foods and iodine-fortified bread. Median (interquartile range) UIC at study entry and 28weeks' gestation was 189μg/L and 172μg/L, respectively. At study entry, median UIC was higher in women taking supplements containing iodine ≥150μg/day compared with those containing iodine <150μg/day (221μg/L vs. 163μg/L, p=.003) and those not taking supplements containing iodine (221μg/L vs. 159μg/L, p<.001). At 28weeks' gestation, the median UIC for the groups was 187, 152 and 141μg/L, respectively (each of the two comparisons yielded p<.001). Total iodine intake (food and supplements) from all women was positively, though weakly, correlated with UIC (r=.23, p<.001). In conclusion, pregnant women in South Australia are iodine sufficient postmandatory iodine fortification of bread. However, without iodine supplementation, it may be difficult to achieve a UIC >150μg/L.