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Breaking down the relationship between dark chocolate and heart health

On Nutrition

Do you enjoy an occasional — or frequent — square or two of dark chocolate? Dark chocolate has a reputation as a heart-healthy food, and research does suggest that there’s some substance behind those claims. Specifically, studies have found that there could be some benefit to consuming chocolate or cocoa for the cardiovascular system, including potentially lowering blood pressure. But while some chocolate lovers view chocolate as a health food, others see it as a guilty pleasure — truly served with a side of guilt. What is the right way to think about this sweet treat?

Dark chocolate’s health halo comes from its cocoa — specifically its cocoa flavanols. Flavanols are a type of polyphenol, and polyphenols are one group of phytochemicals. Many fruits and vegetables contain flavanols, but they are especially rich in tea, wine and cocoa. Some research suggests that flavanols have anti-inflammatory and antioxidant properties and may help protect against cardiovascular disease, which affects both the heart and brain.

While a number of small studies have demonstrated that cocoa can help lower blood pressure, blood sugar and cholesterol, the big question is whether those payoffs will actually help prevent cardiovascular disease down the road. The larger, 21,444-participant COcoa Supplement and Multivitamin Outcomes Study (COSMOS) from Brigham and Women’s Hospital in Boston and Fred Hutchinson Cancer Research Center in Seattle, may provide better answers. The study’s researchers are investigating whether taking daily supplements of 600 milligrams of cocoa flavanols — not chocolate itself — reduces the risk for developing heart disease and stroke, as well as cancer.

For now, how much you need to consume to reap benefits isn’t clear. Some research suggests 200 milligrams of cocoa flavanols daily, about the amount in 2.5 grams of high-flavanol cocoa powder or one-third of an ounce (10 grams) of high-flavanol dark chocolate. However, other research has found that a daily dose of 900 milligrams of flavanols may be necessary.

What does that mean for the average person who enjoys chocolate and hopes they’re getting some health benefit from it? Sadly, 2015 results from the large European Prospective Investigation into Cancer (EPIC-Norfolk) study suggest that the amount of flavanols that the average person in Europe or the United States consumes is unlikely to do much to reduce risk of cardiovascular disease.

Part of the issue with looking for health in the chocolate aisle is that even though cocoa is a key ingredient in milk chocolate and dark chocolate, you can’t really be sure what dose of flavanols you’re getting. Product packaging doesn’t specify amounts of cocoa flavanols, only percent cacao, and variations in how cocoa beans are processed means that the two aren’t necessarily related. The commercially available product CocoaVia is similar to the cocoa flavanol supplement used in the COSMOS study.

Also of note is that it’s still unclear whether bioactive components of the cocoa bean other than flavanols may play a role. Cocoa contains other antioxidants, plus the minerals magnesium, potassium, zinc and iron. COSMOS participants finished taking their supplements — cocoa flavanols, multivitamin or a placebo — at the end of 2020, and the main results are anticipated at the end of 2021.

The bottom line is that if you want to add more flavanols and phytochemicals in your diet, take a broader, more balanced approach. Enjoy some chocolate, but also include a rainbow of fruits and vegetables, as well as whole grains and beans, in your meals — we get different phytochemicals, antioxidants and nutrients from each.