National monitoring of iodine status and salt intake in women of childbearing age in Norway: Results from a cross-sectional study

Purpose Norwegian health authorities implemented voluntary iodization of household salt and salt used in industrially produced bread and bakery products in June 2025. We aimed to assess iodine status in women of childbearing age prior to the new salt iodine fortification program and to estimate the potential impact of the fortification. Methods A nationally representative sample of 3563 mothers of 2-year-old children was drawn from the National Population Register during 2022–2023. A total of 462 women completed an online questionnaire on dietary intake and supplement use, whereof 347 provided casual spot urine sample(s) (92 women provided two). Multivariable quantile regression was used to model differences in the median urinary iodine concentration (UIC) by potential determinants. Iodine and salt intake was estimated using UIC, urinary sodium (UNa) and urinary creatinine concentration (UCrea). Results The median (95% bootstrapped CI) UIC was 104 µg/L (93–115) in non-pregnant, non-lactating women (n = 248), 107 µg/L (76–140) in pregnant (n = 38), and 89 µg/L (68–109) in lactating women (n = 65). Non-users of iodine supplements who were not pregnant or lactating, had median UIC 93 (78–107) µg/L. The median intake of industrially produced bread was 2 slices/day (providing ~ 16 µg iodine). Estimated salt intake varied substantially by estimation method but was higher than recommended for most non-lactating women (87–96%). Conclusions Iodine status at group level was inadequate for pregnant, lactating women and for non-supplement users. The consumption of bread was lower than expected and iodization of salt in bread may not effectively target all women of childbearing age.