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

Abstract

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.

Evaluation of a semi-quantitative food frequency questionnaire to estimate iodine intake

“…In epidemiological studies the difference in iodine excretion between users and non-users of iodine supplementation is often lower than the difference in intake between users and non-users (Nùhr et al, 1993;Pedersen et al, 1995). The reason for this is not clear.…”

Iodine content of traditional Greenlandic food items and tap water in East and West Greenland

“…A diet based on imported food items contributes to an iodine intake level of 40-50 µg/24 h when the iodine content of drinking water is as low as in Greenland (20,32,33). On the other hand, the results of the present study suggest that a diet based on traditional Greenlandic food items (3,15,30) contributes an iodine intake in the order of 200 µg/day, which is only marginally higher than the recommended intake of 150 µg/day (7).…”

“…In Denmark we found tap water iodine content to be highly variable and of considerable importance for regional differences in iodine intake (32). In Greenland fluoride, another halogen, was found in the cryolite quarry in Ivittut and in tap water in Narsaq (22).…”

Variations in urinary iodine excretion and thyroid function. A 1-year study in healthy men

“…The participants lived in Jutland, Denmark, where the iodine intake is moderately low (18). We made no restrictions to their daily or yearly routines and sampling procedures were designed to copy the procedures used in cross-sectional studies of urinary iodine excretion to describe the dispersion included in such studies.…”