May improve blood flow and lower blood pressure

Dark chocolate flavanols can stimulate the endothelium, the lining of arteries, to produce nitric oxide (NO). One of NO's functions is to send signals to the arteries to relax, lowering the resistance to blood flow and thus lowering blood pressure.

Many controlled studies have found that cocoa and dark chocolate can improve blood flow and lower blood pressure, though the effects are usually minor. Cocoa's bioactive compounds may improve artery blood flow and cause a small but statistically significant decrease in blood pressure. However, one study on high blood pressure patients found no effect, so take this with a grain of salt. Given the wide range of studies on this topic, it is clear that more research is required.