Assessing the respective contributions of dietary flavanol monomers and procyanidins in mediating cardiovascular effects in humans: Randomized-controlled, double-masked intervention trial

Background: Flavanols are an important class of food bioactives that can improve vascular function even in healthy subjects. Cocoa flavanols (CFs) are comprised principally of the monomer, (−)-epicatechin (~20%) with a degree of polymerisation of 1 (DP1), and oligomeric procyanidins (~80%, DP2-10). Objective: To investigate the relative contribution of procyanidins and (−)-epicatechin to CF intake-related improvements in vascular function in healthy volunteers. Design: In a randomized, controlled, double-masked, parallel-group dietary intervention trial, 45 healthy men, (18-35 years), consumed once daily for 1 month (a) a DP1-10 cocoa extract containing 130 mg of (−)-epicatechin and 560 mg of procyanidins (b) a DP2-10 cocoa extract containing 20 mg (−)-epicatechin and 540 mg procyanidins or (c) a Control that was flavanol-free with identical micro- and macronutrient composition. (ClinicalTrials.gov NCT02728466) Results: Consumption of DP1-10, but neither DP2-10 nor the Control, significantly increased flow-mediated vasodilation (primary endpoint), and the level of structurally-related (−)-epicatechin metabolites (SREMs) in the circulatory system, while decreasing pulse wave velocity and blood pressure. Total cholesterol significantly decreased after daily intake of both DP1-10 and DP2-10 as compared to the Control. Conclusions: CF-related improvements in vascular function predominantly relate to intake of flavanol monomers and circulating SREMs in healthy humans, but not to the more abundant procyanidins and gut microbiome-derived CF-catabolites. Reduction in total cholesterol was linked to consumption of procyanidins but not necessarily that of (-)-epicatechin.