Metabolic Syndrome (MS) is defined as the association of numerous factors that increase cardiovascular risk 1, such as dyslipidemia, abdominal obesity, systemic arterial hypertension and impaired fasting glycemia. All these altered factors are related to a prothrombotic and proinflammatory condition 23.

MS prevalence in the United States is 21.8% 4, and it has increased strongly over the last few years 5. In Brazil, no data have been reported for the national prevalence, but some studies have shown that MS prevalence at a regional level is approximately 15.8 to 48.3% 67.

It is known that MS etiology includes genetic, metabolic and environmental factors 8. Among environmental factors, diet is one of the main aspects related to the increase in MS in the population 9.

The western diet, which is characterized by the intake of processed meat, refined grains, fried meat and sugar-based desserts, is directly associated with the risk of MS 10. On the other hand, the Mediterranean diet has been inversely associated with MS development 11. Epidemiological studies and control cases have shown a protective effect from dietary patterns characterized by the intake of vegetables, fruit, legumes, whole grain, fiber, fish, lean meat, poultry and fat-free dairy products 1213.

Studies have shown that some dietary components directly influence MS, both as protective factors 1114 and as risk factors 1516. However, no Brazilian study has investigated the influence of dietary intake on MS, only on isolated MS components 171819. Therefore, the aim of this study was to evaluate dietary influence on MS in an adult population sample.

The individuals with MS were older and showed poorer education than those without MS. Income, marital status and gender were similar in both groups. As regards body composition, the individuals with MS showed higher adiposity (> BMI and %BF) and higher MMI. Additionally, lower intake of fruit servings and smaller variety was observed in the diet of individuals with MS (Table 1).

A positive and weak (r < 0.3) correlation was observed among the number of altered MS components, sugar and total lipid intake whereas a negative and week correlation was found between carbohydrate % and the number of fruit servings (p < 0.05). All the other dietary variables did not correlate (p > 0.05).

It was observed that adequate intake of fruit servings and diet variety ≥ 8 food items showed a protective effect for SM. Intake higher than 10% of TCV of saturated fat was found to be a risk factor (Table 2).

In order to explain the protective factor of diet variety for MS, a correlation was made between diet variety and the intake of macronutrients and groups on the food pyramid to evaluate what is the intake profile of individuals who ingested a higher number of different food types. Hence, a positive correlation between diet variety and the intake of vegetables (r = 0.34; p < 0.05), fruit (r = 0.32; p < 0.05), fibers (r = 0.22; p < 0.05), dairy products (r = 0.20; p < 0.05) and HEI (r = 0.20; p < 0.05) was observed, and a negative correlation for the intake of legumes (r = -0.11; p < 0.05), meat (r = -0.15; p < 0.05) and grains (r = -0.19; p < 0.05) was found. There wasn't a significant correlation for the intake of macronutrients, oil servings and sugar.

The main finding of the present investigation was the protective effect of fruit intake and increase in diet variety and the harmful effect of saturated fat intake on the chances of developing MS.

Levy-Costa et al. (2005) observed the presence of excessive sugar and saturated fat intake and insufficient fruit and vegetable intake in the Brazilian diet 32. Our results appear to confirm that this dietary habit is directly associated with the higher risk for MS in this population.

Other studies have shown a protective effect from fruit intake against MS 333435, indicating that such intake is related to the reduction of almost all MS components (TG, hypertension, WC and glucose) 1834. The main protective factor from fruit probably results from the intake of soluble fibers 33. The intake of this fiber type can reduce glycemia from lower absorption and digestion of carbohydrates, thus reducing insulin secretion, in addition to reducing dyslipidemia 36. Additionally, the potassium present in this food type can also reduce arterial pressure 37. The intake of food with low glycemic loads, such as fruit, is related to smaller WC 38, possibly due to the greater satiation 39 and lower energy density provided by this food type 40.

When the diet is evaluated as a whole, the food patterns that are characterized by large amounts of fruit, vegetables and whole grains, such as the Mediterranean diet, are inversely associated with MS prevalence 11414243 whereas the western diet, characterized by low fruit intake, is positively associated with MS 10.

Another protective factor identified in the present study was diet variety, evaluated by the number of different food types ingested in 24 h. To our knowledge, this is the first study reporting diet variety as a protective factor against MS development, and further studies are necessary to explain the possible mechanisms involved. Analysis of the results showed that greater diet variety was correlated with a better quality diet (HEI) and with food groups considered to be healthy, such as the intake of vegetables, fruit, fibers and dairy products. These food groups have been reported by other studies as prevalence reducers and protective factors against MS development 333437394445. Furthermore, the diet variety could be influenced for the fruit intake isolated, which is also a protector factor for MS. The present study also identified an inverse correlation of diet variety with meat intake, thus showing that this food type increases the chances for MS development 15.

A study conducted with older individuals showed that the inadequate intakes of several nutrients were associated with lower diet variety. It means that recommendations to increase diet variety may be necessary for elderly people to achieve adequate nutrient intakes 46.

Another possible cause for the protective effect of diet variety could be the fact that the individuals whose had the higher diet varied showed greater fractioning during the evaluated day. Studies show that increased fractioning is responsible for decreasing fasting glycemia 47, plasma concentration of postprandial insulin, plasma concentrations of LDL-c and total cholesterol 48. Additionally, greater fractioning increases postprandial thermogenesis 48 and can foster the negative energy balance, thus providing weight loss in the long term and as a positive factor for MS reduction.

The present study showed increased chances of MS development in individuals who ingest > 10% of saturated fat TCV. This association may have occurred due to the fact saturated fat increases the visceral adipose tissue in greater proportion than other fat types, since it reduces the activation of PGC-1α (PPARγ-coactivator), an important oxidative metabolism regulator. Thus, fatty acid and glucose oxidation is decreased, and accumulation in tissues and circulation is increased 49. Hence, saturated fat intake would increase the visceral adipose tissue, which contributes to MS development.

Additionally, saturated fat increases insulin resistance (IR) compared to monounsaturated fat 50, because it activates serine kinases, thus inhibiting the insulin phosphorylation cascade, decreasing glucose uptake and increasing glycemia 51. Another contributing factor to IR is the increase in inflammation, apoptosis and oxidative stress of adipocytes 49.

Some epidemiological studies showed that total dietary fat intake is positively associated with MS in Japanese Brazilian populations 52 and in other countries 16, and this positive association is directly related to saturated fat 53, which is in agreement with our results.

The present study showed that individuals with MS had poorer education, were older and presented higher adiposity (BMI, %BF and WC) and muscle mass (MMI). Another studied reported a positive correlation between BMI and muscle mass, showing that obese individuals present not only higher fat mass, but also show higher muscle mass (kg) 54.

Epidemiological studies have shown the influence of age on MS 5556, and this occurs due to the fact that ageing is related to body fat mass and lean mass redistribution with rapid increase in visceral intra-abdominal fat, which is proinflammatory and related to insulin resistance 57.

The relation between poorer education and hyperadiposity has been observed by other studies 58. This relation can be explained by the fact that individuals with poorer education consume less fruit, vegetables and legumes; i.e. their diet is of lower quality 59. The intake of these food groups were protective factors against MS in the present study.

The present study has some limitations. For this research has used the convenience sample, it do not allow generalizations for the Brazilian population. Furthermore, results from several studies using different food inquiry techniques showed underestimation in intake reports, both in males and females. However, the underestimation is primarily identified among obese individuals and particularly among females 60. Considering that all the methods that evaluate dietary intake are, to some extent, imperfect and that a gold standard does not exist in nutrition, patient diet was evaluated by analysis of 24-hour recalls. This fact represents the principal limitation in our study, since one 24-hour recalls do not detect dietary intake variations.

In this study, recommended intake of fruit and high diet variety are protective factors and high intake of saturated fat is a risk factor for metabolic syndrome.

Future proposals for intervention should consider lifestyle changes with adequate eating habits in these individuals.

BMI: Body mass index; MS: Metabolic syndrome; WC: Waist circumference; NCEP-ATPIII: National cholesterol education program-adult treatment painel III; HEI: Healthy eating index; TCV: Total caloric value; HDL: High density lipoprotein cholesterol; TG: Triglycerides.

The authors declare that they have no competing interests.

EPO wrote the manuscript, KCPM corrected and revised the final manuscript. LVAS made the statistical analysis and corrected the manuscript. RCB was the mentor of the work and advisor of the authors. All authors read and approved the final manuscript.