||Mental stress has been shown to induce cardiovascular events, likely due to its negative
impact on vascular function. Flavanols, plant-derived polyphenolic compounds, improve endothelial
function and blood pressure (BP) in humans, however their effects during stress are not known. This
study examined the effects of acute intake of cocoa flavanols on stress-induced changes on vascular
function. In a randomised, controlled, double-blind, cross-over intervention study, 30 healthy men
ingested a cocoa flavanol beverage (high-flavanol: 150 mg vs. low-flavanol < 4 mg (?)-epicatechin)
1.5 h before an 8-min mental stress task). Forearm blood flow (FBF), BP, and cardiovascular activity
were assessed pre- and post-intervention, both at rest and during stress. Endothelial function (brachial
flow-mediated dilatation, FMD) and brachial BP were measured before the intervention and 30 and
90 min post-stress. FMD was impaired 30 min post-stress, yet high-flavanol cocoa attenuated this
decline and remained significantly higher compared to low-flavanol cocoa at 90 min post-stress.
High-flavanol cocoa increased FBF at rest and during stress. Stress-induced cardiovascular and BP
responses were similar in both conditions. Flavanols are effective at counteracting mental stressinduced endothelial dysfunction and improving peripheral blood flow during stress. These findings
suggest the use of flavanol-rich dietary strategies to protect vascular health during stress.