The results of the present study demonstrate that, while there was a difference in dietary antioxidant intake between Brazilian men and women, mean vitamin A and vitamin E intake was below the reference values, regardless of gender, age, skin color, economic status, social class, nutritional state and region of the country.
Brazil has been following the worldwide tendency of an extended life expectancy and ageing of the population [27
]. The low intake of antioxidants, especially among individuals over 60 years of age, can have serious public health consequences. In elderly individuals, besides the reduction in the capacity to prevent and remove oxidation products, there is also a greater possibility of generating reactive oxygen species and a lesser dietary antioxidant intake related to a series of factors inherent to ageing, such as a reduction in ingestion and the absorption capacity of the digestive tract [27
]. Thus, the low intake identified in the BRAZOS study may be an indicator that antioxidant intake should be improved.
In the present study, Brazilian people had significantly lower intakes of antioxidants. This may be consequence of consumption underreporting. However, other factors can particularly affect the intake. The simple fact of living longer is associated with less functional abilities, and other conditions, i.e. being widowed and with children living geographically apart can reduce motivation for cooking. Financial issues, such as living on a fixed/low income, increased dependence on social security or pension may also contribute to a greater nutrient inadequacy [30
Currently, obesity is considered the second greatest cause of avoidable death in modern society. According to data from the 2002-2003 Brazilian Family Budget Survey [2
], 40.6% of the population is overweight, with greater prevalence among individuals between 50 and 70 years of age. The BRAZOS study reveals a similar frequency of overweight and obesity (57.7%) among men and women over 40 years of age [22
]. Obesity and the consequent non-communicable chronic diseases stemming from it do not only affect the mortality rate, but are also associated to concomitant diseases that represent a huge economic burden on the healthcare system and society alike. Costs with care and medication are significantly higher for patients with excess weight, increasing with each unit of body mass index in the shape of a "J" curve [31
In western societies, the increase in obesity and associated chronic disease has been related to an increase in calorie intake stemming from the choice of unbalanced diets, the intake of foods with a high energy density rich in fats and carbohydrates [32
] as well as a progressive increase in the portions of food [6
]. It should be stressed that the greater total food and calorie intake by obese individuals is not necessarily associated to the consumption of foods that are a source of micronutrients, as evidenced in the present study. In general, there is an insufficient intake of sources of vitamins and minerals, which, in the long run, could increase the risk of the development or aggravation of metabolic disorders.
Conversely, the relation between anthropometric nutritional state and food intake data or the concentrations of vitamins and minerals is controversial. A number of studies have found lower serum levels of carotenoids in obese individuals in comparison to individuals within the ideal weight range, with no significant difference regarding food intake [31
]. Thus, greater serum inadequacy of these antioxidants is believed to be associated with a greater metabolic demand rather than oxidative stress in obese individuals [39
Traditionally, vitamin A deficiency is related to alterations in visual acuity and the immune system. Its role as a modulator of fat tissue, causing greater adipogenesis, has recently been demonstrated [40
]. Moreover, individuals with a lower plasma concentration of this vitamin may be at greater risk for cardiovascular mortality [41
], as vitamin A participates in the prevention and slowing of the atherogenesis process through the inhibition of the oxidation of LDL-cholesterol and a reduction in the formation of foam cells [20
]. The data from the present study corroborate previous studies carried out in Bambuí (Minas Gerais, Brazil) [43
] and Ponta Porã (Mato Grosso do Sul, Brazil) [44
] regarding the high proportion of individuals with low vitamin A intake (92.4%, 99.8% and 87.5%, respectively). The most likely explanation for this finding, even in regions with a large amount of food sources of this vitamin, such as the northern and northeastern regions, is more related to cultural and eating habits than economic factors [45
]. According to the National Demographic Children's and Women's Health Survey [47
], The greatest prevalence of vitamin A deficiency was found in the southeastern region and the lowest was found in the northern region.
Vitamin E is a lipophilic antioxidant in cell membranes and has considerable importance to the neutralization of peroxynitrites and protection from oxidative stress, particularly the sweeping away of free radicals [10
]. This is the first study to evaluate the dietary intake of vitamin E among the Brazilian population. Two surveys in the United States found intakes of vitamin E superior to the values found in our study. The Third National Health and Nutrition Examination Survey (NHANES III 1988-94) reported a median intake for men and women (31 to 50 years old) of 11.7 mg and 9.1 mg, respectively, while the Continuing Survey of Food Intakes by Individuals (CSFII 1994-96) described lower median intake in this same age (9.3 mg for men and 6.8 mg for women) [9
]. A British cohort study that evaluated vitamin intake at 4 and 43 years of age identified that those with the lower intake had higher risk for hypertension and higher waist circumference. In this study, the highest intake of vitamin E, both in childhood and adulthood, was found in women (57%) [49
]. These findings are different from our results, which indicate similar intake in both genders. In another study, Morris et al found that higher intake of vitamin E, from both food and supplements, was associated with lesser change in cognitive score/year in elderly [50
]. In our study, the mean intake was similar to the values reported for median intakes in the lower quintile.
In order to achieve the current recommendation for vitamin E intake proposed by the DRIs, it is necessary to consume large quantities of food sources of this vitamin, such as oils, oil-rich foods and whole-grain cereals [51
], which are also a source of unsaturated fatty acids. Thus, a diet rich in fruit and vegetables, but with a low intake of these food sources, likely contains less than 15 mg of α-tocopherol. Some of these foods, such as nuts, are generally not part of Brazilian cultural habits. Soybean oil and margarine are the main sources of fats in Brazil [2
], and vitamin E requirements increase as polyunsaturated fats intake increases. Furthermore, a diet rich in fats/ oils may not be of advantage due to their high-energy or caloric value [9
]. The supplementation or fortification of foods with vitamin E may be an interesting strategy for improving dietary adequacy [53
]. However, it also should be taken into consideration that vitamin E is a difficult element for assessing. Low intakes may be due to underreporting of energy and consequently of fat intake, its primary source, or difficulty in estimating amounts of oils and fats added to food preparation and actual amount absorbed into the cooked product [9
Selenium is an essential component for the formation of glutathione peroxydase, which is an enzyme involved in the detoxification of hydrogen peroxide and lipid hydroperoxidation as well as an important co-enzyme for the synthesis of proteins related to the immune and neurophysiological systems [55
]. In the BRAZOS study, we found a small proportion of individuals (13.4%) with a low intake of this micronutrient, even lower than that reported by Fernandes et al. (21.1%) in adults with metabolic syndrome [33
]. However, caution should be exercised when analyzing this finding, as the amount of selenium in foods is related to its presence in the soil and the amount found in a given food source differs depending on its region of origin [56
]. For instance, in the case of the Brazil nut, which is an excellent source of this mineral, Freitas et al. [57
] identified contents ranging from 0.003 mg to 5.12 mg in 100 g (range of 1:17000). Moreover, studies have found that the states of São Paulo and Mato Grosso have lower concentrations of this nutrient in the soil [58
]. In the present study, selenium intake was highest in the northern region, probably due to the greater consumption of fish and cashews.
More than half of the sample, especially those over 60 years of age (data not shown) had an insufficient zinc intake, which corroborates the findings described by Cozzolino [58
]. Rats with zinc deficiency have a reduced tolerance to glucose with no alteration in insulin production in response to glucose injection [59
]. Likewise, individuals with type II diabetes may have a lower serum level of zinc [60
]. More recently, Marreiro et al. [61
] found low plasma concentrations of zinc in obese individuals and demonstrated that the supplementation of this mineral reduces insulin resistance.
Vitamin C (ascorbic acid) is one of the most important hydrosoluble antioxidants. It is capable of inhibiting the formation of hydroxyl free radicals and protecting from the peroxidation of lipids and LDL by sequestering peroxyl radicals [62
] in joint action with vitamin E [15
]. It should be stressed that the proportion of individuals with low vitamin C and E intake may be underestimated, as the percentage of regular smokers was 25% [25
], which is a condition that increases the need for these vitamins [63
The present study has limitations that should be considered. Incomplete information about micronutrients in software's database should always be accounted for since the American nutritional reference database used does not include the regional peculiarities of some typical Brazilian foods. However, the researchers took care to adjust the nutritional aspects by means of a laboratory analysis of foods reported by the population, such as regional fruit, dishes, spices, delicacies, etc. Another important aspect is there was no extrapolation to other age groups and/or stages of life, as only individuals over 40 years of age were included. Although an adequate data collection method for the estimation of mean dietary intake [64
], the evaluation of intake based on a single 24-hour recall does not reflect habitual or long-term intake and does not allow an analysis of intake intra-variability. Moreover, although mean nutrient intake is adequate for the description of intake among groups, it does not allow comparisons with reference values (EAR) for the identification of the prevalence of deficiencies. Other substances not evaluated in this study should be considered in further analyzes due to their role in modulating oxidative stress, such as copper, manganese, as well as that bioactive. Finally, plasma concentrations of the antioxidants were not determined, which does not allow ensuring the clinical outcome.