Cacao contains fat, sugars, carbohydrates and protein, so it is known and have been used as an energy food as it's energy content is high; around 2000kJ. It also contains catechin, fiber, carbohydrates, B vitamins and anti-oxidant-like substances in high amounts. Other substances like calcium, phosphates, vitamins A, C and D occur in smaller amounts.

Cacao have the same anti-oxidants, flavonoids, as red wine, which have been shown to possibly protect against heart disease. A fourty grams serving of milk chocolate typically contains around 400 mg of antioxidants, similar to the amount in red wine. While dark chocolate contains more than twice that amount, close to the amount in black tea. However, the manufacturers have to be careful when they are processing the chocolate products so as not to remove the flavonoids that are present. These antioxidants can protect the heart and blood vessels. In fact, the flavonoids are more effective than vitamins, such as vitamin C, in preventing the oxidation of cholesterol present in the low-density lipoproteins (LDL) and very-low-density lipoproteins. Atherosclerosis studies have suggested that oxidation of these lipoproteins is an vital step in the formation of the artery-clogging plaque. The main family of flavonoids that gives chocolates their antioxidant properties is the procyanidins, that have a basic unit of a three ring structure. The mature cocoa bean have dimers, trimers, tetramers, and other larger compounds that has more units. Tetramers were the compounds that have the most effect in preventing the oxidation that produces free radicals, that can wreak in blood vessel walls, a process that encourages the rupturing of atherosclerotic plaque. Chocolate's tetramers and larger procyanidins also help relax the inner surface of blood vessels, according to studies in isolated tissues headed by C. Tissa Kappagoda of the University of California, Davis School of Medicine.

Penny Kris-Etherton and her colleagues at Pennsylvania State University in State College, plan to report yet another benefit that dark chocolate have to the heart. In the 24 volunteers whom they studied, diets enriched with dark chocolate or cocoa powder, which is essentially unsweetened chocolate, raised the individuals' high-density lipoprotein (HDL) cholesterol, the so-called good cholesterol. "This is important," Kris-Etherton says, "because a higher ratio of HDLs to LDLs is associated with a decreased risk of heart disease." The high levels of HDLs would help in preventing the fats from clogging of the arteries.

However, the Harvard research also suggested that people who eat too much chocolate have a lower life expectancy. Chocolate's high fat content means that the indulgence can lead to obesity, and thus lead to an increased risk of heart disease. As people often say too much of anything is indeed no good for anyone.  

However, Alan Crozier from the University of Glasgow is doing research on the different type of chocolate and they have found that flavonoids in certain chocolates may be present but is not taken up by the body. More information is given in the latest news on chocolate.