Orientador: Profa. Dra. Rosane Marina Peralta

Data da Defesa: 21/03/2014


RESUMO GERAL: INTRODUCTION - Clinical and epidemiological studies have often shown an inverse relationship between the consumption of plant foods and the prevalence of non-communicable chronic diseases such as cancer, diabetes and cardiovascular diseases. This relationship is a function of the presence of bioactive compounds that are found in these foods as vitamins, minerals, carotenoids, phytosterols, sulfur compounds, organic acids and phenolic compounds. Among these, the phenolic compounds are notable for their high antioxidant capacity and higher consumption in the usual diet. However, clinical studies in which the effects of isolated antioxidant compounds were evaluated either failed to detect significant beneficial effects to health or detected a much less pronounced action when compared to those studies in which these compounds were present in the diet. This fact has been explained as resulting from the variety of the bioactive compounds present in the diet as a whole and also as a consequence of synergistic interactions. This observation can be explained by the variety and synergistic actions of the bioactive compounds consumed in the diet as a whole. Studies on the content and antioxidant capacity of the diet in developing countries are scarce. Furthermore, in most studies the phenolic compounds were extracted with organic solvents a procedure that does not simulate the normal physiological conditions and does not reflect the real availability of those compounds for absorption. AIMS - The objectives of this study were: 1. To estimate the consumption of total flavonoids and the phenolic antioxidant capacity as well as the main ingredients of the Brazilian diet of plant origin subjected to in vitro digestion; 2. To estimate the intake of antioxidant vitamins and minerals allowed by the Brazilian diet; 3. To investigate the impact of in vitro digestion in comparison with the simple aqueous extraction on the content of phenolics, flavonoids and total antioxidant capacity of plant foods commonly consumed in the Brazilian diet. MATERIAL AND METHODS - We used data from 34,003 individuals, aged 10 or more years, in the Household Budget Survey from 2008 to 2009 to estimate the consumption of foods and beverages of plant origin. To estimate the intake of antioxidant vitamins and minerals 188 foods were selected considering their usual intake form. For quantification of the levels of antioxidant vitamins and minerals of selected foods the composition tables of national and international foods were used. For estimating the consumption of phenolics, flavonoids and the total dietary antioxidant capacity of the diet (TDAC), 36 food preparations and beverages of vegetable origin were selected. Selection was based on the potential presence of phenolics in its composition and on the fact that they had been reported individually or in conjunction with similar foods by at least 100 informants. Three samples of each food in three different local supermarkets or three different popular brands of processed products were selected and submitted to the cooking process or not, according to their usual consumption. Subsequently they were processed to acquire the pasty consistency and subjected to the in vitro digestion process protected from light. The water extraction was carried out by subjecting the samples to the same conditions of the samples subjected to in vitro digestion with the same volume proportions of gastrointestinal samples and solutions, 3 using only deionized water. After the extraction, the samples were centrifuged for 10 minutes and filtered through Whatman number 1 paper. The analyses of phenolics, flavonoids and total antioxidant capacity (TAC) estimated by the FRAP assay (Ferric Reducing Antioxidant Power) and TEAC (Trolox Equivalent Antioxidant Capacity) were performed on the same day, protected from light. RESULTS AND DISCUSSION - The estimated averages of the daily consumption of antioxidant vitamins were 309 µg of vitamin A, 9.3 mg of vitamin C and 5.3 mg of vitamin E. The values of the main antioxidant minerals were 11.7 mg of zinc, 107.6 µg of selenium, 1.35 mg of copper and 2.9 mg of manganese. The major source of vitamin A was beef liver (16.7%). The major sources of vitamin C were juices (34.8%) and the fruits orange (11.9%) and acerola (10.9%). Beef was the main source of zinc (32%) and selenium (16.3%). Rice was the main source of vitamin E (32.4%). Beans were the main source of copper (27.8%) and manganese (25.3%). The daily consumption of flavonoids and phenolics was estimated at 2.3 g and 374 mg/day, respectively, which are comparatively higher values when compared to developed countries. The total antioxidant capacity estimated by the FRAP assay was 10.3 mmol/day and by the TEAC assay 9.4 mmol/day. The beverages, especially coffee, followed by beans, rice and bread were the most important sources of antioxidants. Fruits and vegetables showed a low contribution (4-6 %) for the intake of phenolics and total antioxidant capacity. Measurement of the impact of in vitro digestion on the phenolic contents and total antioxidant capacity of foods of plant origin revealed higher contents in the groups of cereals, legumes, vegetables, fruits and tuberous vegetables and lower levels or absence of difference in the group of beverages. CONCLUSION - Estimates of the consumption of phenolics demonstrated that they are quantitatively the major antioxidants in the Brazilian diet when compared to vitamins and mineral antioxidants and that the ingestion of these compounds depends not only on their contents in the food, but also on the daily amount of each food consumed per capita. The results of the simulated digestion of foods in comparison with the aqueous extraction showed that contents resulting from the extraction with organic solvents may not reflect the probable contents available for absorption. Thus, it is emphasized that more studies are needed to estimate more precisely the antioxidant content of foods in the usual diet to the quantities actually available for absorption. This is important for evaluating the true extent of the physiological and health beneficial effects of antioxidants. Key words – antioxidant capacity, Brazilian diet, phenolics, flavonoids, minerals, vitamins. 


Artigos Publicados Vinculados a Tese:

Analysis of a whole diet in terms of phenolic content and antioxidant capacity: effects of a simulated gastrointestinal digestion

Total antioxidant capacity and phenolic content of the Brazilian diet: a real scenario