Has mandatory fortification with iodine made a difference? : results from two cohort studies in the Darwin area

![CDATA[Background/Aims: The re-emergence of iodine deficiency in Australia led to the mandatory fortification with iodine of salt used in bread making in 2010. We assessed urinary iodine concentration in two cohorts of young adults living in the Darwin area before and after fortification. Methods: Spot urine samples were collected from participants in the Aboriginal Birth Cohort (urban and remote Aboriginal) and the Top End Cohort (urban non-Indigenous) as part of planned longitudinal follow-up. This occurred before and after fortification. We used the WHO criterion of median urinary iodine concentration (MUIC) > 100 mcg/L in spot urine samples to classify population groups as replete for iodine. Results: There were 590 urine samples before and after fortification. MUIC improved for all groups: in men from 47, 78 and 93 μg/L to 98, 128 and 132 μg/L in remote Aboriginal, urban Aboriginal and urban non-Aboriginal participants respectively. Similarly, in women, median concentrations increased from 55, 58 and 63 Jlg/L to 89, 127 and 94 μg/L respectively. All groups were classified as deficient prior to fortification. Following fortification, urban men, both Aboriginal and non- Aboriginal, and urban Aboriginal women were classified as replete. However remote living Aboriginal people and urban non-Aboriginal women continued to be classified as deficient. Conclusions: Although there was improvement across all the groups post fortification, some groups remain in the mild deficiency range. This is most concerning in women of childbearing age as iodine requirements increase in pregnancy and lactation.]]