Spanish researchers put 42 men and women on a diet that included 40 grams of unsweetened cocoa powder (about 1.4 ounces) mixed with skim milk daily, or plain skim milk. After one month, those who drank the cocoa-flavored milk had lower levels of inflammatory markers associated with heart disease than those drinking the milk alone.
That result was critical because the participants, whose average age was about 70, were at high risk of cardiovascular disease because they had diabetes and three or more risk factors for heart disease, including smoking, high blood pressure, high levels of LDL "bad" cholesterol (more than 160 milligrams per deciliter), low levels of HDL "good" cholesterol (below 35 milligrams per deciliter), obesity or a family history of early coronary heart disease.
The inflammatory markers, called adhesion molecules, are proteins that cause white blood cells to stick to the walls of the arteries, which can lead to the formation of atherosclerotic plaques, explained Shelley McGuire, an associate professor of food science and nutrition at Washington State University and a spokeswoman for the American Society for Nutrition.
"One of the major strengths of the study was they were measuring adhesion molecules, which we have recently learned are very important in the formation of atherosclerosis," McGuire said. "Another strength is that the study was randomized and controlled. Because of this, we can pretty confidently say there was something in the cocoa powder that had an effect."
The researchers also found that the cocoa powder group had an increase in HDL cholesterol, which can help reduce levels of LDL cholesterol and has been shown to have anti-inflammatory, antioxidant properties.
The study is published in the November issue of the American Journal of Clinical Nutrition.
During the study, participants didn't take additional vitamins or supplements, and the only cocoa-containing products they consumed were those provided by researchers.
Previous research has suggested chocolate may be beneficial for heart health because it contains anti-inflammatory chemicals called polyphenols.