Iodine and Selenium Intake in a Sample of Women of Childbearing Age in Palmerston North, New Zealand after Mandatory Fortification of Bread with Iodised Salt

Abstract

Iodine deficiency is a worldwide public health problem, which has long been observed in many parts of the world, including New Zealand (NZ). The aim of this study was to assess iodine and selenium intake among women of childbearing age in Palmerston North, New Zealand post mandatory fortification of bread with iodised salt. Fifty women of childbearing age completed a researcher-led questionnaire, including a semi-quantitative food frequency questionnaire. Iodine and selenium were analysed in 24-hour urine samples. The median urinary iodine concentration (UIC) was 65 μg/l with 30% below 50 μg/l; representing mild iodine deficiency according to the World Health Organization. The estimated median daily iodine intake (130 μg/day) was higher than the Estimated Average Requirement (100 μg/day) and higher than seen in women prior to fortification. The median excretion of selenium (32 μg/day) was slightly above level suggested as adequate (30 μg/day) and estimated median intake (57 μg/day) was higher than Estimated Average Requirement (50 μg/day). Selenium and iodine excretion were significantly correlated (Spearman’s rank order; r(50) = 0.547, p < 0.001). The major contributors to iodine intake were milk (36%), bread (25%) and fish/seafood (15%). Participants had a mean intake of 2.5 slices of bread/day, which contributed approximately 14 to 20 μg of iodine. The majority of participants (74%) had iodised salt at home, but less than half (48%) used iodised salt exclusively. In conclusion, despite the mandatory fortification of bread with iodised salt in NZ, UIC of the study population indicates iodine deficiency although their estimated dietary intakes appear adequate. It is essential that government initiatives to improve iodine status are evaluated for their efficacy.