Iron intake: dietary intake and its association with insulin resistance and metabolic syndrome in the era of mandatory fortification

Author(s)

Diva Aliete dos Santos Vieira

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Saúde Pública (FSP/CIR)
• Defense date: 2016-12-09

Examining board members

Regina Mara Fisberg; Marilisa Berti de Azevedo Barros; Josefina Aparecida Pellegrini Braga; Elizabeth Fujimori; Marcelo Macedo Rogero

• Advisor: Regina Mara Fisberg

Abstract

Introduction: The mandatory fortification of foods with iron was initiated in Brazil in 2004 with order to combat this micronutrient deficiency. However, some studies indicate that excessive consumption of iron can be related to the development of metabolic syndrome, insulin resistance and alterations in lipid metabolism. Objectives: To assess the iron intake before and after the implementation of the mandatory fortification policy, to investigate the association of haem, nonhaem iron and total iron intake with metabolic syndrome and its components, and to evaluate the role of haem, nonhaem iron, and total iron intake in insulin resistance mediated by interleukin 6, leptin and malondialdehyde. Methods: Data were drawn from two cross-sectional population based studies (ISA-Capital 2003 and 2008), conducted with a representative sample of residents of São Paulo, of both sexes and aged over 12 years old. Dietary intake was measured by two 24-hour dietary recall. Socioeconomic, demographic and lifestyle data were obtained through a structured questionnaire. Blood samples were collected after a 12-hour fasting for biochemical analysis and blood pressure, weight, height and waist circumference were measured. The analytes analysed were fasting plasma glucose, fasting serum insulin, plasma triglyceride, high-density lipoprotein cholesterol, malondialdehyde, C-reactive protein, interleukin-6 and serum leptin. All analyses were performed with Stata®, version 13 e Mplus®, version 7.4, and a p-value < 0.05 was considered statistically significant. Results: The iron intake mean increased in all the population in the post fortification period. The prevalence of inadequate iron intake decreased by over 90 per cent in men in all 9 analyzed age groups. Although despite the substantial decrease (over 63 per cent ), women in reproductive age remain with a high inadequate intake (34 per cent ). Higher total iron intake (OR=3.98, 95 per cent CI=1.21 13.12) and nonhaem iron intake (OR=2.92, 95 per cent CI=1.107.72) were positively associated with hyperglycaemia. There was a positive association between higher haem iron intake with metabolic syndrome (OR=2.39, 95 per cent CI=1.105.21) with elevated triglyceride levels (OR=2.51, 95 per cent CI=1.065.91). Haem, nonhaem iron and total iron intake had a direct and positive effect on levels of interleukin-6 and negative effect on malondialdehyde levels. There was an indirect effect of haem, nonhaem iron and total iron intake on insulin resistance mediated by interleukin-6. Conclusion: This study suggests that the different types of dietary iron are associated with major risk factors of noncommunicable diseases. Thus, monitoring of iron addition in wheat and maize flour is essential to guarantee a safe iron intake for all the population. (AU)

• FAPESP's process: 13/06979-9 - The effect of biofortified food consumption in the nutritional status of iron and vitamin A in pre-school children
• Grantee: Diva Aliete dos Santos Vieira
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)