Recently some researcher suggests that the key ingredients responsible for regaining healthy arterial function in patients with diabetes are chemicals called "flavanols." 

Cocoa naturally contains "flavanols", antioxidant chemicals which are also found in some fruits and vegetables, green tea and red wine, and has been linked with health benefits by other studies.

They said, diabetic patients with severely impaired arteries who drank specially formulated cocoa daily for a month regained normal function.  They thought that the flavanols could be working by increasing the production of nitric oxide, a body chemical which tells arteries to relax and widen, and results demonstrate that dietary flavanols might have an important impact as part of a healthy diet in the prevention of cardiovascular complications in diabetic patients.