Iodine Nutrition Improves in Latin America

Abstract and Introduction

Iodine deficiency has been a public health problem in most Latin American countries. Massive programs of salt iodization have achieved great progress toward its elimination but no consistent monitoring has been applied.We used the ThyroMobil model to visit 163 sites in 13 countries and assess randomly selected school children of both genders 6–12 years of age. The median urinary iodine concentration (8208 samples) varied from 72 to 540 μg/L. One national median was below the recommended range of 100–200 μg/L; five were 100–200 μg/L,and seven were higher than 200 μg/L, including three greater than 300 μg/L. Urinary iodine concentration correlated with the iodine content of salt in all countries. Median values of thyroid volume were within the normal range for age in all countries, but the goiter prevalence varied markedly from 3.1% to 25.0% because of scatter. The median iodine content of salt from local markets (2734 samples) varied from 5.9 parts per million(ppm) to 78 ppm and was greater than 15 ppm in 83.1% of all samples. Only seven countries had higher than 15 ppm iodine in 80% of the samples, and only three had greater than 15 ppm in at least 90%. Iodized salt was available at retail level in all countries but its median iodine content was within the recommended range (20–40 ppm) in only five. This study, the first to apply a standardized assessment strategy to recent iodine nutrition in Latin America, documents a remarkable success in the elimination of iodine deficiency by iodized salt in all but 1 of the 13 countries. Some iodine excess occurs, but side effects have not been reported so far, and two countries have already decreased their legal levels of salt iodization and improved the quality control of iodized salt, in part because of our results. The present work should be followed by regular monitoring of iodine nutrition and thyroid function, especially in the countries presently exposed to iodine excess.

Iodine deficiency is recognized as the most common cause of preventable brain damage and mental retardation. It also causes goiter, damaged reproduction, and other disorders, all together termed iodine deficiency disorders (IDD).^[1] Iodine deficiency is a permanent natural phenomenon widely distributed around the world and the association of severe iodine deficiency with endemic cretinism was recognized as a geographical–epidemiologic fact long ago.^[2] Even a moderate degree of iodine deficiency may cause subtle impairment of neuro-intellectual development,^[3] from inadequate supply of thyroid hormones to the brain during fetal and early postnatal life. At the beginning of the 1900s it was estimated that at least 1,500,000,000 people, approximately one third of the world's population, were at risk of iodine deficiency, 655,000,000 were affected by goiter, 11,000,000 were overt cretins, and another 43,000,000 had some degree of mental retardation.^[4]

The elimination of IDD as a public health problem by the year 2000 was advocated at the UN World Summit for Children in 1990, the Quito Declaration in 1994, and again at the UN General Assembly in May 2002, with a new target of 2005. Most of the affected countries' governments have committed themselves to meet this goal. Substantial progress has been achieved in many countries, but recent assessments indicate that much remains to be done. According to a recent World Health Organization (WHO) report, 35.2% of the world's population continues to have various degrees of iodine deficiency (urinary iodine below 100 μg/L).^[5]

In the early twentieth century, iodine deficiency was recognized as a public health problem in most of the Latin American countries,^[6] and in the 1950s to 1970s, most passed legislation on iodized salt,^[7] arbitrarily establishing a wide range of iodization levels, likely because of poor information on the daily physiologic needs for iodine ( Table 1 ). Unfortunately, after some initial success in most of the countries, there was poor comprehension of the problem and,therefore, no serious commitment for monitoring either the iodization of the salt or its impact on health. Hence, approximately 30 years later, as shown in Table 1 , only a few countries were nearing iodine sufficiency, and goiter prevalence had not significantly changed.^[7–9] In 1999, the WHO reported that despite significant regional progress, iodine deficiency remained a public health problem in 19 countries in the region.^[10]

Most Latin American countries have reassessed their iodine status over the last 15 years and have implemented programs for the control of IDD. Great progress has been made, particularly by the aggressive push for iodized salt use, but problems remain, such as weak governmental support and lack of effective monitoring of salt iodization in some countries, that threaten the effective and sustained elimination of IDD in the region. Data on the present situation, however, are incomplete because regular monitoring is carried out in only a few countries. Moreover, different methods were used to measure iodine in urine and salt, and goiter was evaluated only by palpation.

The World Health Organization/United Nations Children's Fund/International Council for the Control of Iodine Deficiency Disorders (WHO/UNICEF/ICCIDD) has recommended assessment and monitoring of iodine nutrition by three variables: the fraction of households using adequately iodized salt, the concentration of iodine in representative urine samples (urinary iodine), and the prevalence of goiter.^[11,12] Urinary iodine and goiter prevalence were used to evaluate the iodine nutrition status in Europe in the ThyroMobil model, which has proven to be a convenient and efficient model for standardized and rapid evaluation.^[13] The ThyroMobil is a van equipped with an ultrasound and facilities for collecting and storing urine samples, which travels to selected areas in a country; a trained physician performs all the thyroid ultrasounds and supervises the sampling and data collection. Hence, we decided to use this model to assess the progress attained in the Americas conducting a standardized evaluation of the status of iodine nutrition. The specific objectives were: (1) to measure in each country the three main variables, iodine content of salt, median urinary iodine, and prevalence of goiter; (2) to increase the awareness of IDD by the national authorities and the general population through a process of social mobilization; and(3) to reinforce the commitments toward the sustainable elimination of IDD.

© 2004 Mary Ann Liebert, Inc.

Cite this: Iodine Nutrition Improves in Latin America - Medscape - Aug 01, 2004.