Grape polyphenols improve blood pressure and vascular function in men with metabolic syndrome

Abstract

Men (n=24, 30–70y) with metabolic syndrome (MetS) were randomly allocated to consume either a freeze‐dried grape polyphenol powder (GRAPE) or a placebo for 30 days in a double blind manner. After a 3‐wk washout, they were allocated to the alternate treatment. Participants maintained their usual diet and physical activity during the study and abstained from consuming polyphenol‐rich foods. MetS parameters and markers of vascular endothelial function [flow‐mediated vasodilation (FMD) of the brachial artery, plasma total nitric oxide (NOx), plasma soluble intercellular adhesive molecule‐1 (sICAM‐1) and vascular cell adhesive molecule‐1 (sVCAM‐1) were measured]. There was a significant (p= 0.002) decrease in systolic blood pressure (BP), greater FMD response (p= 0.000), and reductions in circulating sICAM‐1 concentrations (p= 0.017) during the GRAPE compared to the placebo period. In addition changes in sICAM‐1 concentrations between periods were negatively correlated with absolute FDM changes (r = −0.479, P < 0.025). Although NOx concentrations were not different between periods, changes in systolic BP were negatively correlated (r = −0.437, p < 0.05) with changes in NOx concentrations indicating the vasodilating properties of NOx. These results suggest that GRAPE polyphenols may potentiate vasorelaxation and reduce circulating adhesive molecules, as well as reduce BP and improve vascular dysfunctionGrant Funding Source : California Table Grape Commission