Dark chocolate may help peripheral artery disease, study shows

Here's some health news to brighten your holiday weekend: A small trial found that eating a dark chocolate bar helped those with peripheral artery disease — a common condition that impairs blood circulation — walk longer on a treadmill compared to when they ate a milk chocolate bar. But outside experts caution that the study findings are preliminary and need to be replicated before knowing whether they're valid.

Studies on the potential health benefits of dark chocolate have been plentiful in recent years with findings so promising that Brigham and Women's Hospital researchers recently received a $20 million research grant from industry to launch a clinical trial involving 18,000 people to see whether taking cocoa supplements can lower the rate of heart attacks and strokes better than placebos.

But this latest trial, published in the Journal of the American Heart Association, was on the other end of the spectrum involving just 20 patients. "The study results are certainly intriguing, but it would need to be replicated in a much larger population of patients with peripheral artery disease and for much longer period of time to know if there's any meaningful improvement from eating chocolate," said Dr. Mark Creager, director of the vascular medicine progam at Brigham and Women's Hospital and president-elect of the American Heart Association.

There is a possible scientific explanation for the findings: Components in dark chocolate, called polyphenols, improved blood flow in peripheral arteries that run through the arms and legs when the Italian study researchers examined the action of these antioxidants in petri dishes.

While that's promising, Creager cautioned not to read too much into that finding. "I've personally done a number of studies with vitamin C, showing that it improved blood vessel function," he said, "but long-term studies of vitamin C supplement use" didn't find that it offered any heart benefits — nor have other antioxidant supplements like vitamin E.

But those benefits seen from eating a 40 gram dark chocolate bar — about the size of a regular 200-calorie Hershey bar — were very modest: Patients walked an average of 39 feet farther and 17 seconds longer on a treadmill two hours after eating the dark chocolate compared to what they walked earlier in the day. They didn't walk any further or longer, on the other hand, after eating the milk chocolate.

Such a small difference could be explained by a placebo effect, Creager said, since the study participants likely knew which kind of chocolate they were eating. (Most of us can tell the difference between dark and milk chocolate.) They may have also seen the headlines that dark chocolate has potentially beneficial effects.

Eating a chocolate bar a day with all its added sugars, calories, and saturated fat can also be problematic for those trying to lose or maintain their weight — a key component for managing heart disease risk.

The American Heart Association recommends that men consume no more than 150 calories per day from added sugars and women should consume no more than 100 calories from added sugar per day to lower heart disease risk. A typical chocolate bar made in this country provides 94 calories from added sugar.

"Everyone would love to believe that eating a chocolate bar a day will improve their health, but I don't believe that will prove to be the case," Creager said.