The aim of this is study is to evaluate the long-term effects of grape polyphenols in the modulation of markers of metabolic syndrome. Most of the previous works about polyphenols have only considered a fraction of polyphenols, i.e., extractable polyphenols. As a consequence, an important amount of dietary polyphenols, the so-called non-extractable polyphenols are ignored. In contrast, the effect of both extractable and non-extractable polyphenols will be considered in this study. Also, studies on the long-term effect of grape polyphenol on markers of metabolic syndrome have been mostly conducted in animals, so clinical trials on this topic are needed.

Fifty supposedly healthy volunteers with at least two cardiometabolic risk factors were recruited. The cardiometabolic risk factors used to select the subjects are described below.

The whole intervention will be divided in 2 periods, control (CTR) and dried and milled grape pomace (GRAPOM). The two periods will have a duration of 6 weeks. During the CTR period, subjects will follow their normal dietary habits and samples will be collected at the beginning and at the end. No proper placebo could be found for the product, so this CTR period was chosen. During the GRAPOM period, the subjects will daily consume 8 g of the product solved in water and samples will be collected at the beginning and at the end.

Inclusion Criteria:

At least two of the following requirements:

• BMI ≥ 25 kg/m2.
• Fasting glucose values ≥ 100 mg/dL.
• Triglycerides ≥ 150 mg/dL.
• HDL-cholesterol: ≤ 50 mg/dL women, ≤ 40 mg/dL men.
• Blood pressure: systolic ≥ 130 mm Hg or diastolic ≥ 85 mm Hg.

Exclusion Criteria:

• Subjects with a pharmaceutical treatment set to modify blood pressure, lipid profile or glucose.
• Volunteers participating in other studies or weight loss plans.
• Pregnant or breastfeeding women.