A multi-centre pilot study of iodine status in UK schoolchildren, aged 8–10 years

PURPOSE Iodine, as an essential constituent of thyroid hormones, is required for brain development. Iodine status is low in some UK population groups, notably in teenage girls, women of childbearing age and pregnant women. We aimed to assess iodine status of UK schoolchildren as there are no data on children below 14 years of age. METHODS Children (boys and girls) aged 8-10 years were recruited to a cross-sectional study from schools in three areas of the UK (Omagh, Northern Ireland; Glasgow, Scotland, and Guildford, South-East England). Spot urine samples, for measurement of urinary iodine concentration, were collected in the winter months (November 2012 to March 2013) and in the summer, in Omagh only (September 2013). A food frequency questionnaire was completed. RESULTS A total of 168 schoolchildren provided 165 urine samples. The median urinary iodine concentration was 161 µg/L in winter samples (n = 134) and 127 µg/L in summer samples (n = 31). The median urinary iodine concentration for the whole group was 144 µg/L, weighted to account for the unequal proportion of samples from the two seasons. The children are classified as iodine-sufficient by WHO criteria (100-199 µg/L), even in the summer. Milk intake was positively associated with iodine status. CONCLUSIONS This pilot study suggests that iodine deficiency is unlikely to be a problem in UK children aged 8-10 years. This could be a result of higher intake of milk, the principal UK dietary iodine source, in this age group than in teenagers and adults. Further assessment of iodine status in a representative sample of UK schoolchildren is required.