Wine grape pomace flour (WGPF) is a fruit byproduct high in fiber and antioxidants. The effect of WGPF consumption was tested on blood biochemical parameters including oxidative stress biomarkers. In a 3-month intervention study, 27 male volunteers, each with some components of metabolic syndrome, consumed a beef burger supplemented with 7% WGPF containing 3.5% of fiber and 1.2 mg GE/g of polyphenols (WGPF-burger), daily during the first month. The volunteers consumed no burgers in the second month, and one control burger daily in the third month. At baseline and after these periods, there were evaluated metabolic syndrome components, plasma antioxidant status [2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity (DPPH),uric acid, vitamin E, vitamin C], and oxidative damage markers [advanced oxidation protein products (AOPP), oxidized low-density lipoproteins (oxLDL), malondialdehyde (MDA)].

The intervention was carried out at workplaces in Santiago, Chile. Workers were informed about the study and invited to participate. Initially, 34 male workers meeting all criteria agreed to partake, however 27 workers completed the study. Seven volunteers quit the study because three disliked the blood sampling procedure, two were sent to work abroad, one left the workplace, and one presented gastrointestinal symptoms associated with WGPF-burger consumption.

The volunteers entered a longitudinal trial consisting of two treatment periods of 4 weeks, separated by a third four-week wash-out period. For the first 4 weeks, they consumed one WGPF-burger daily, then they were washed-out and finally they consumed one control-burger daily during 4 weeks. They were asked to maintain their regular eating habits and lifestyle during the study, except for the daily intake of burgers during the treatment periods. The burgers were eaten in replacement of red or processed meat consumption, or in addition to their regular meal when it did not contain meat products. During the washout period, all subjects consumed their usual diet. Burger intake was supervised every day at lunch at the canteens of the workplaces. On weekends, participants were asked to consume burgers at home with their regular meals. In addition, compliance with burger consumption was carefully monitored by frequent calls from the dietitian.

Blood samples were obtained at weeks 0, 4, 8, and 12 for analysis. Participants had clinical, nutritional, and anthropometric evaluations at the beginning and the end of the study.

Inclusion Criteria:

• The inclusion criteria were having at least one of the five components of metabolic syndrome and a BMI between 25.0 and 39.9 kg/m2

Exclusion Criteria:

• Exclusion criteria were use of drug therapy for diabetes mellitus, hypertension, or dyslipidemia and intake of pharmacological treatment with drugs that modify plasma antioxidant capacity or inflammation.