The approach of Valentine’s Day each year brings the latest crop of “chocolate is good for your heart” articles. We would all like to believe that a sweet treat protects the heart and arteries. But that notion isn’t completely supported by the evidence.
Some studies show a strong connection between eating chocolate and less heart disease. In a survey of nearly 5,000 American adults, those who said they ate chocolate five times a week were 40% less likely to have ever had a heart attack or to have needed an artery-opening procedure (Clinical Nutrition, December 2010). A similar trend was seen in a large German study. In these types of studies, though, it is impossible to tell if eating chocolate protects the heart and arteries or if people who eat chocolate also do other things that are responsible for this protection.
What about clinical trials, which tend to yield better evidence? A number of trials have tested whether dark chocolate (50% to 70% cocoa) lowers blood pressure more than a cocoa-free placebo. A newly published analysis combined the results of 15 such trials. It showed that daily doses of dark chocolate lowered systolic blood pressure (the top number of a blood pressure reading) by 5 points and diastolic pressure (the bottom number) by 3 points — but only among people with high blood pressure. Chocolate had no effect among people with normal blood pressure (BMC Medicine, published online June 28, 2010).
Lab studies are all over the map. They suggest possible ways that chocolate might protect the heart and arteries — providing antioxidants, stimulating artery walls to generate artery-relaxing nitric oxide, inhibiting the activity of a blood pressure–raising enzyme — but no definitive proof that it does.
A review in the June 2010 issue of Circulation highlights the uncertainty. Researchers from the Medical University of South Carolina concluded that eating dark chocolate is a promising but unproven way to treat or prevent heart disease.
And consider these two issues: First, it’s one thing to eat or drink chocolate when you’re in the mood for it. It’s another thing to take it like medicine. In an Australian trial comparing a daily square of dark chocolate (70% cocoa) to a capsule of lycopene-rich tomato extract, half the participants said they found it difficult to eat 2 ounces of chocolate every day (BMC Complementary and Alternative Medicine, published online July 8, 2009). Second, eating chocolate would be a high-calorie way to protect the heart — 50 grams of dark chocolate (about 2 ounces) delivers 300 calories. Add that to your diet every day without cutting back elsewhere, and you could pack on 20 to 30 pounds over the course of a year.
For now, we recommend eating chocolate as a snack or treat. Don’t take it as medicine. Mix up chocolate with other snacks that could do some good for your heart and arteries, such as pumpkin seeds, raisins, almonds, or pears.