Urinary iodine excretion and individual iodine supplementation among elderly subjects: a cross-sectional investigation in the commune of Randers, Denmark.

Several studies have demonstrated that the iodine intake is relatively low in Denmark. However, the results are difficult to interpret because no information has been given on the frequency of individual iodine supplementation. We performed a cross-sectional study of elderly subjects living in the commune of Randers, Denmark. Urinary iodine excretion was measured in the 423 participants (185 males, 238 females) and a careful history was taken on any possible intake of supplementary iodine. The median urinary iodine excretion was 48.3 micrograms/g creatinine for the whole population (40.8 micrograms/g creatinine in males, 53.2 micrograms/g creatinine in females). In the part of the population that did not take iodine supplementation (46.7%) the median value was 36.1 micrograms/g creatinine (males 33.8; females 38.8). Regular iodine supplementation taken as an iodine-containing vitamin/mineral tablet was found in 30.8% of the population. This increased the urinary iodine excretion to a median level of 80.5 micrograms/g creatinine (males 62.0; females 88.0). The study shows that the basic iodine intake level is overestimated if individual iodine supplementation is not taken into account. Such supplementation may lead to median iodine excretion values that seem reasonable, even if the iodine intake of the part of the population not taking iodine (in this study, nearly half of the population) is low.