Chocolate has gotten a lot of media coverage in recent years because it's believed that it may help protect your cardiovascular system. The reasoning being that the cocoa bean is rich in a class of plant nutrients called flavonoids.
Flavonoids help protect plants from environmental toxins and help repair damage. They can be found in a variety of foods, such as fruits and vegetables. When we eat foods rich in flavonoids, it appears that we also benefit from this "antioxidant" power.
Antioxidants are believed to help the body's cells resist damage caused by free radicals that are formed by normal bodily processes, such as breathing, and from environmental contaminants, like cigarette smoke. If your body does not have enough antioxidants to combat the amount of oxidation that occurs, it can become damaged by free radicals. For example, an increase in oxidation can cause low-density lipoprotein (LDL), also known as "bad" cholesterol, to form plaque on the artery walls.