Iodine intake and status of UK women of childbearing age recruited at the University of Surrey 1 in the winter

21 As intra-thyroidal iodine stores should be maximised before conception to facilitate the increased 22 thyroid-hormone production of pregnancy, women who may become pregnant should ideally consume 23 150 µg iodine/day [US Recommended Dietary Allowance (RDA)]. As few UK data exist in this 24 population group, our aim was to assess iodine intake and status in women of childbearing age in a 25 cross-sectional study at the University of Surrey. Total iodine excretion was measured from 24-h urine 26 samples in 57 women; iodine intake was estimated by assuming that 90% of ingested iodine was 27 excreted. Average iodine intake was also estimated from 48-h food diaries that the women completed. 28 The median urinary-iodine concentration (63.1 µg/L) classified the group as mildly iodine deficient by 29 WHO criteria. By contrast, the median 24-h iodine excretion (149.8 µg/24-h), suggested a relatively 30 low risk of iodine deficiency. Median estimated iodine intake, extrapolated from urinary excretion, was 31 167 µg/day, whereas it was lower, at 123 µg/day, when estimated from the 48-h food-diaries. Iodine 32 intake from food diaries and 24-h iodine excretion were strongly correlated (r=0.75, p<0.001). Intake 33 of milk, eggs and dairy products was positively associated with iodine status. The iodine status of this 34 UK cohort is probably a best-case scenario as the women were mostly nutrition students and were 35 recruited in the winter when milk-iodine content is at its highest; further study in more representative 36 cohorts of UK women is required. Our study highlights a need for revised cutoffs for iodine deficiency 37 that are method-and age-group specific.