4 year study by the Brigham and Women's Hospital in USA identified a 27% reduction in death from cardiovascular disease in people who routinely consumed a cocoa flavanol supplement.  There were more than 21,000 participants in the trial who were randomised to take two 500mg cocoa flavanol capsules daily, a multivitamin, neither or both.

Amongst those that took their cocoa flavanol tablet consistently, there was a 15% reduction in total cardiovascular events, and a 39% reductino in death from cardiovascular disease.  Across all participants taking the cocoa flavanol supplement (some not always taking it daily), there was an overall 27% reduction in death from cardiovascular disease.

Flavanols are naturally occuring compounds found in plant-based foods such as cocoa, tea, grapes plus other fruits and vegetables.  Flavanol levels in cocoa are naturally higher than in many other food sources.

Earlier studies by others have found cardiovascular benefits for cocoa flavanols on blood pressure and blood vessel dilation.

Original article: https://www.brighamandwomens.org/about-bwh/newsroom/press-releases-detail?id=4127