Several studies have shown dark chocolate is heart healthy.
Eating Chocolate Might Protect the Cardiovascular System
In 2005, the results of a study conducted by researchers at the Athens Medical School in Athens, Greece was published. This paper examined the effect of flavonoid-rich dark chocolate on the cardiovascular system. The researcher concluded that consumption of dark chocolate “may exert a beneficial effect on endothelial function in healthy adults” and that “chocolate consumption may exert a protective effect on the cardiovascular system” as a whole.
In February 2006, Dutch scientists published a study in the Archives of Internal Medicine which examined diet of 470 elderly men. The research examined the health outcomes of the men using data from the larger Zutphen Elderly Study in the Netherlands. The results were that the men who consumed foods made from cacao beans, such as hot chocolate, chocolate bars, or chocolate pudding were healthier. They had lower blood pressure and a 50% lower risk of death than those men that did not eat chocolate.
Although more research needs to be done on this topic, these preliminary results suggest that if you desire a healthy heart, dark chocolate is the key, likely due to the unique phytonutrients within cacao.