This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Cocoa is a rich source of antioxidant polyphenols and frequent consumption of cocoa and dark chocolate is associated with significant reductions in mortality and improvements in a number of CVD risk factors including blood pressure and vascular endothelial function. The primary goal of this study is to examine the effects of cocoa-derived polyphenols on several markers of cardiovascular risk, including cardiovascular and hormonal responses to psychological stress. This project builds on recent studies showing significant reductions in blood pressure after consumption of dark chocolate and cocoa. Grassi et al reported that 24-hour ambulatory blood pressure was significantly reduced by flavonol-rich dark chocolate in both normotensive and hypertensive individuals. This suggests that the hypotensive effects of cocoa are not restricted to controlled resting conditions, and that lower blood pressure may also be evident during exposure to stress in daily life. We propose to enroll 35 healthy adults, ages 40-65, who are typical of the US population (having body mass index in the overweight to obese range but without diabetes or other systemic disease). Our goal is to complete testing on 30 subjects who will be exposed to high polyphenol dark cocoa or a matched low polyphenol chocolate for 4 weeks each in a crossover design. The design includes a screening visit and a 2 -4 week washout between treatments. High polyphenol cocoa (22 g/d) will be delivered in a sugar-free cocoa beverage and a 37 g bar of dark chocolate. Primary outcomes to be measured before randomization and at the end of each treatment period include: cardiovascular and hormonal reactivity to acute stressors, mood, vascular endothelial function, pulse wave amplitude, and several other CVD risk factors measured in blood, saliva and urine. These include renin/ACE/angiotensin, lipids, inflammatory cytokines, insulin, glucose, HbA1c, and urinary stress hormones.