A 2015 Norfolk study published in Heart magazine linked higher consumption of chocolate (up to 3.5 ounces per day, dark or milk chocolate) to a lower risk of future cardiovascular events, such as heart disease and stroke. Twelve percent of participants who fell into this higher level of chocolate consumption experienced or died of cardiovascular disease during the 11-year study, compared to 17.4% of participants who didn’t include chocolate in their diets.
Scientists are working to determine why chocolate may be linked to better heart health. Flavonoids, a polyphenol also found in tea, red wine, blueberries, nuts, and some other fruits, could be responsible. They’re present in the cacao beans that are used to produce the cocoa powder in chocolate. Researchers have associated flavonoids with beneficial health effects, such as lower blood pressure, heightened blood flow to the brain and heart, and fewer blood clots. They also improve cognition and fight damage to cells in the body.
However, as Chief Medical Editor of Harvard Health Publications Howard LeWine, MD, commented, “We don’t yet know enough to put eating chocolate on par with eating fruits, vegetables, and whole grains.” That’s because most of the studies concerning chocolate consumption and heart disease are purely observational. While these types of studies can discover and report connections, they cannot determine cause and effect.
There could be other factors at play than chocolate consumption. For example, LeWine noted that participants in the Norfolk study who didn’t eat chocolate showed, on average, higher weight, higher likelihood of diabetes, more inflammation that damages arteries, and less frequency of physical activity than those who ate chocolate. Any of these factors might be responsible for the frequency of heart disease in the population. To determine a causal link, a randomized, clinical trial would be needed.
In 2015, the Women’s Health Initiative began just such a trial to study cocoa flavonol and multivitamin supplement consumption, heart health, and cancer risk in women across a five-year period. “We’ll be testing them in a capsule form,” JoAnn Manson, chief of the Division of Preventive Medicine at Brigham and Women’s Hospital, noted in conversation with NPR. That will test the effects of cocoa flavonols without the sugar, fat, and calories chocolate contains.
In the meantime, authors of the Norfolk study assured, “There does not appear to be any evidence to say that chocolate should be avoided in those who are concerned about cardiovascular risk.”