Original articleIodine intake in the adult population. [email protected] study
Introduction
The World Health Organization (WHO) estimates that some 2 billion persons, including 285 million children, are at risk for iodine deficiency, defined as a urinary iodine excretion in affected populations of less than 100 μg/L. According to the WHO, a population is considered mildly deficient in iodine when the median urinary iodine excretion is 50–99 μg/L, moderately deficient when this median is 20–49 μg/L, and severely deficient when it is below 20 μg/L.1
The individual prediction of iodine intake is difficult, as the amount of iodine in water and food can vary by a factor of 100.2, 3 The standard way to measure iodine intake in a particular population is by measuring urinary iodine excretion, expressed in μg/L in a casual urine sample. The resulting value, which represents 70–80% of daily iodine intake, can vary widely among persons from the same community.
Spain has experienced known iodine deficiency in many of its regions throughout its history.4, 5 Numerous studies over recent years have shown that, though iodine intake as measured by urinary iodine excretion appears to have increased, this intake still varies greatly between regions.6, 7 However, to date no nation-wide study has yet been undertaken. The aim of this study, therefore, was to evaluate iodine intake, as measured by urinary iodine excretion, and its conditioning factors in a representative sample of the whole adult population of Spain.
Section snippets
Population
The [email protected] Study is a national, cross-sectional, population-based survey conducted in 2009–2010 in 16 of the 17 autonomous communities (AC) in Spain. A cluster sampling design was used to select participants, forming a representative random sample of the population census from Spanish population. Of the eligible adults, 55.8% attended for examination. Of these, 9.9% were excluded by protocol (institutionalized, severe disease, pregnancy or recent delivery). Age, sex and geographical origin
Urinary iodine and age
The mean and median urinary iodine for the whole population were 135.2 ± 85.8 μg/L and 117.2 μg/L, respectively. The mean urinary iodine/urinary creatinine ratio (I/Cr ratio) was 134.9 ± 127.8, and the median was 104.2.
The urinary iodine did not differ significantly between men and women, but the I/Cr ratio was significantly greater in women 109.0 ± 95.6 vs. 153.4 ± 145.9 (median 86.3 vs. 117.8).
The urinary iodine increased significantly with age (p = 0.02), up to 70 years of age. This increase was
Discussion
Numerous studies throughout the 20th century have shown the presence of iodine deficiency in various different areas of Spain.4, 5, 6, 7 More recent studies have detected the persistence of subclinical iodine deficiency disorders (IDD).16, 17, 18 Local studies carried out in different places in Spain6, 7 now suggest that iodine intake has increased, though it still varies between the AC. A recent report by the WHO classifies Spain as a country that is free of iodine deficiency and with an
Statement of authorship
FS, GRM, IV, AG, AB, EB, AC, RC, RC, LC, CC, MC, ED, JF, SG, JG, RG, GG, ALA, MTML, EM, IMP, EO, GPM, MSR, SV, JAV and JV participated in the design, selection of subject and in the coordination and field study. CGR and EGF measured the biochemical variables. FS, GRM, CGR and EGF performed the statistical analysis. All authors helped to write the manuscript and read and approved the final manuscript.
Conflicts of interest
The authors declare that no conflict of interest exist.
Acknowledgments
CIBER de Diabetes y Enfermedades Metabólicas Asociadas and CIBER Fisiopatología de la Obesidad y Nutrición are ISCIII projects.
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