Urinary iodine excretion: A valuable tool for monitoring salt iodisation programme

Background National surveys report that more than 90% of families in India access iodised salt (IS). Surveys of school children reported that median urinary iodine (UI) excretion was satisfactory in around 80% and high in 20% of the districts. Methods Between 2017 and 2021, based on data from 2 separate studies (A and B), UI was estimated in urban low-middle income families residing in South Delhi who had purchased IS from the market and used it for >1 year, or received IS or iron-fortified IS (DFS) from the research team and used it for >1 year. Spot urine samples were collected in the morning in both these groups; UI excretion was estimated using the microplate method based on the Sandell-Kolthoff reaction. Results Median baseline UI in those who purchased IS in the market was 234 µg/L in 2017 (Study A) and 235 µg/L in 2019 (Study B). In those who received the salt from the research team and used it in Study A, median UI in 2019 was 183 µg/L in IS users and 182 µg/L in DFS users; while in Study B, median UI in 2021 was 139 µg/L in IS users and 125 µg/L in DFS users. In both studies, UI after intervention was significantly different (lower) from baseline but not different between the IS and DFS groups. Conclusion There was a decrease in median UI between 2019 and 2021. This might be due to increasing awareness of the adverse consequences of excess iodine intake, and the salt industry complying with the Food Safety and Standards Authority of India's revised standards, which require the iodine content of salt at the manufacturer level to be between 20 and 30 ppm.