Iodine nutritional status in Brazil: a meta-analysis of all studies performed in the country pinpoints to an insufficient evaluation and heterogeneity

Abstract

Objectives: Iodine deficiency disorder (IDD) is the result of an inadequate dietary intake of iodine, which physiological consequences are endemic goiter and thyroid dysfunction. The objective of this study was to a analyze studies that assessed the status of Brazil's population iodine nutrition and IDD prevalence. Materials and methods: Systematic review using PRISMA statement. Electronic database: PubMed, Medline, SciELO and Lilacs. Quality of studies: Newcastle-Ottawa Scale. Metaanalysis was carried out with R Core Team Statistical Software, version 3.1.0 (2014). The summary measure (WMD) and its confidence interval (CI) of 95% were calculated. The "Funnel plot" graph assessed publication bias and heterogeneity. Results: Seventeen papers were eligible: pregnant women (2), school children (9), adults/elderly (4) and preschool children/infants (2). Geographic distribution: North (1), Northeast (1), Midwest (2), Southeast (13), South (3). Twenty-three thousand two hundred seventy-two subjects were evaluated between 1997 and 2013 and all have use urinary iodine (UI) measurement. However, only 7 studies could be included in meta-analysis, all from Southeast region. The overall prevalence of IDD in school children in southeast region was 15.3% (95% CI, 13-35%), however this data had an important heterogeneity, expressed by the I² Statistic of 99.5%. Conclusion: Only few studies have been performed and enrolled populations from south/southeast region of Brazil. The actual IDD prevalence analysis is complex because it was detected bias due influence of individual studies and very high heterogeneity. IDD might still be high in some areas but this remained unknown even after this meta-analysis evaluation. The generation of a national program for analysis of iodine status in all regions is urgently required. Arch Endocrinol Metab. 2015;59(1):13-22

Iodine Nutritional Status in Schoolchildren from Public Schools in Brazil: A Cross-Sectional Study Exposes Association with Socioeconomic Factors and Food Insecurity

“…A recent meta-analysis has shown that the actual ID prevalence in Brazil is very complex due to the high heterogeneity and bias of available studies (20). Several factors and regional variations may influence iodine intake that must be considered in Brazil, such as changes in diet, differences in goitrogen consumption (including cassava), geographical and social demographic characteristics, and the availability of processed foods-all factors that may lead to a coexistence of ID and EII, depending on the regional characteristics (20).…”

“…Several factors and regional variations may influence iodine intake that must be considered in Brazil, such as changes in diet, differences in goitrogen consumption (including cassava), geographical and social demographic characteristics, and the availability of processed foods-all factors that may lead to a coexistence of ID and EII, depending on the regional characteristics (20). Without doubt, the scarcity of new representative national data is worrisome, mainly because most of the previous estimates were based on subnational data that may under-or overestimate the extent of ID (20).…”

Thyroid disorders in Brazil: time for action

“…Meanwhile, there have been other surveys in several locations indicating lower or higher levels of urinary iodine and differences in the prevalence of goiter. [8][9][10] In conclusion, to the best of our knowledge, no recent national data on the prevalence of goiter or on urinary iodine levels is available to enable rational actions towards thyroid health.…”

The Hypothyroid Brain

“…Iodine, a trace element, is indispensable for thyroid hormone synthesis, and must be acquired via food intake. A deficiency in this element results in the malfunction of the thyroid gland, hypothyroidism and neurodevelopmental disorders [8] .…”