You may have seen recent newspaper articles stating that dark chocolate is good for the heart.
These articles were based on a study of 20 patients with mild high blood pressure who were given either dark or white chocolate for 15 days. The patients given dark chocolate had significant falls in their systolic and diastolic blood pressures during a 24-hour period. They also lowered their LDL cholesterol and insulin resistance. The authors attribute these benefits to the flavonoids present in the dark chocolate. No improvements were seen in the patients given white chocolate, which does not contain flavonoids.
A number of prior observational studies have suggested that the antioxidant properties of flavonoids protect against atherosclerosis and its resulting complications of heart disease and stroke. Such observational studies can only suggest benefits; proving the value of flavonoids requires controlled trials such as the one described above.
Does this study prove the benefits of flavonoids in dark chocolate and indicate that we should add dark chocolate to our diets? Although the study was carefully done, questions remain. This study was apparently carried out in Italy, but newspapers cite one author from the Nutrition Center at Tufts School of Medicine in Massachusetts. Is the mention of a well-known American institution an attempt to increase the credibility of the study? The number of participants was small and the effects were measured for only 15 days. Would blood pressure remain lower with long-term addition of dark chocolate to the diet? The same group of researchers found a small fall in blood pressure but no decline in LDL cholesterol when dark chocolate was eaten by healthy subjects with normal blood pressures. Several other studies reported no fall in blood pressure when healthy volunteers ate dark chocolate.
Should we add dark chocolate to our diets? I don't think so. Adding chocolate also adds unnecessary calories. In addition, the dark chocolate products available in this country contain little flavonoids. If you want to increase the flavonoid content of your diet, try fruits and vegetables, purple grape juice, and tea.