Elsevier

Clinical Nutrition

Volume 31, Issue 6, December 2012, Pages 882-888
Clinical Nutrition

Original article
Iodine intake in the adult population. [email protected] study

https://doi.org/10.1016/j.clnu.2012.04.004Get rights and content

Summary

Background & aims

To date no nation-wide study has yet been undertaken in Spain to estimate the iodine deficiency. The aim was to evaluate iodine intake and its conditioning factors in a representative sample of the whole adult population.

Methods

The [email protected] Study is a national, cross-sectional, population-based survey conducted in 2009–2010 in Spain.

Results

The median urinary iodine (UI) was 117.2 μg/L. Iodized salt (IS) was consumed by 43.9% of the population. The median UI in those who consumed IS and in those who did not consume IS was 131.1 and 110.8 μg/L respectively (p < 0.0001). The likelihood of having UI levels above 100 μg/L was significantly associated with the intake of IS (OR = 1.47) and milk at least once a day (OR = 1.22). Within each individual autonomous communities, the median UI levels in those who consumed IS correlated significantly with the median levels of those who did not consume IS (r = 0.76, p = 0.001).

Conclusions

Though strictly speaking, Spain should be considered within the category of a country having an adequate iodine intake, the current value is too close to the cut point and does not guarantee that those groups with a greater need for iodine will have the required intake of iodine.

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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