Abstract
Ensuring sufficient iodine intake is a public health priority, but we lack knowledge about the status of iodine in a nationally representative population in Norway. We aimed to assess the current iodine status and intake in a Norwegian adult population. In the population-based Tromsø Study 2015–2016, 493 women and men aged 40–69 years collected 24-h urine samples and 450 participants also completed a food frequency questionnaire (FFQ). The 24-h urinary iodine concentration (UIC) was analyzed using the Sandell–Kolthoff reaction on microplates followed by colorimetric measurement. Iodine intake was estimated from the FFQ using a food and nutrient calculation system at the University of Oslo. The mean urine volume in 24 h was 1.74 L. The median daily iodine intake estimated (UIE) from 24-h UIC was 159 µg/day (133 and 174 µg/day in women and men). The median daily iodine intake estimated from FFQ was 281 µg/day (263 and 318 µg/day in women and men, respectively). Iodine intake estimated from 24-h UIC and FFQ were moderately correlated (Spearman rank correlation coefficient r = 0.39, p < 0.01). The consumption of milk and milk products, fish and fish products, and eggs were positively associated with estimated iodine intake from FFQ. In conclusion, this shows that iodine intake estimated from 24-h UIC describes a mildly iodine deficient female population, while the male population is iodine sufficient. Concurrent use of an extensive FFQ describes both sexes as iodine sufficient. Further studies, applying a dietary assessment method validated for estimating iodine intake and repeated individual urine collections, are required to determine the habitual iodine intake in this population.
Highlights
Iodine is an essential trace element and it is required for the production of thyroid hormones which are essential for regulation of energy metabolism in adults [1].Too little and too much iodine can both increase the risk of thyroid dysfunction, and iodine deficiency can lead to a variety of health consequences known as iodine deficiency disorders (IDDs) [2]
In subanalysis, excluding those who reported that their urine collection was incomplete or completed less than 90% of the food frequency questionnaire (FFQ), and participants having very high or low total energy intake, we found that the estimated intake of iodine, calculated from 24-h urine excretion or the FFQ, was not significantly different from the whole sample
The iodine intake estimated from 24-h urinary iodine concentration (UIC) describes a mildly iodine deficient female population, while the iodine intake findings based on these two methods indicate that the adult male study population have iodine intake within recommended values
Summary
Iodine is an essential trace element and it is required for the production of thyroid hormones (thyroxine and triiodothyronine) which are essential for regulation of energy metabolism in adults [1].Too little and too much iodine can both increase the risk of thyroid dysfunction, and iodine deficiency can lead to a variety of health consequences known as iodine deficiency disorders (IDDs) [2]. Before 1990, only a few countries were iodine sufficient, but comprehensive progress has been made since the primary intervention strategy for IDD control, i.e., universal salt iodization was adopted in. In Norway, IDD used to be endemic, but fortification of animal fodder since the early 1950s (2 mg of iodine per kilogram) contributed to the elimination of goiter and the prevention of IDD due to consumption of milk and dairy products [10]. Milk, dairy products, fish, and fish products have been the main sources of iodine in the diet of Norwegians, contributing about 80% of the total iodine intake [11,12]. Iodized salt is an important source of iodine in many countries, iodine fortification is only permitted in table salt (five milligrams of iodine per kilogram) in Norway
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