In December, 2016, the Iodine Global Network (IGN) published its new map of global iodine nutrition based on median urinary iodine concentration (mUIC) in school-aged children. Notably, the status of the UK, which was classified as mildly iodine deficient in 2014–15 (mUIC 50–99 μg/L), had become adequate by 2016 (mUIC 100–299 μg/L). The reason for this apparently rapid improvement lies in the different data sources used; data that showed mild deficiency in 2014–15 came from spot-urine samples from 737 girls aged 14–15 years from nine UK centres (mUIC 80·1 μg/L), whereas the 2016 data were based on spot-urine samples from 458 boys and girls aged 4–18 years, which were collected in year 6 of the UK National Diet and Nutrition Survey (NDNS).
Bath, S; Rayman, M et al. Has the UK really become iodine sufficient? The Lancet Diabetes and Endocrinology. (2017). http://www.thelancet.com/journals/landia/article/PIIS2213-8587(17)30133-X/fulltext?dgcid=etoc-edschoice_email_June