Iodine fortification of cattle feeds is also widely used to increase
iodine concentrations in both organic and conventional milk.
According to a 2013 study, 10 countries have iodine excess, 111 countries have sufficient iodine intake, 9 countries are moderately deficient, 21 are mildly deficient, and none are considered severely deficient, as defined by a median urinary
iodine concentration of 100 - 299 μg / L in school - aged children (1).
On the other hand, the World Health Organization recommends
urine iodine concentration (UIC) to monitor an individual's iodine status (2).
90 % of ingested iodine is excreted via renal pathways, such that median spot urinary
iodine concentrations (UIC) will serve as a biomarker for recent dietary iodine intake (1).
Another study from western Australia (a region that has previously been shown to be iodine replete) measured urinary
iodine concentration (UIC) of 98 women at 6 months postpartum and checked their thyroid status both postpartum and 12 years later [23].
Iodine concentrations are higher in breast tissue even than in the thyroid, to provide plenty of iodine for the breastfeeding infant (29).