People with peripheral artery disease (PAD) who ate a dark chocolate bar were able to slightly increase the time and distance they walked a couple of hours later, compared to people who ate milk chocolate, researchers found.
“Nutrients are key components of health and disease,” said Dr. Lorenzo Loffredo, the study’s lead author from Sapienza University in Rome.
He and his colleagues write in the Journal of the American Heart Association that compounds known at polyphenols, which are much more plentiful in dark chocolate than milk chocolate, may have something to do with the improved performance.
“In the context of atherosclerosis, following an appropriate diet is crucial for reducing the burden of vascular disease,” Loffredo wrote in an email. This study supports that idea, he said, as eating polyphenol-rich nutrients led to improved blood flow in the legs.
About one in five people ages 70 years and older living in Western countries is affected by PAD, the researchers write. In addition to being a risk factor for heart attacks and strokes, the condition can cause legs to hurt and cramp while walking.
For the new study, the researchers recruited 14 men and six women who were in their late 60s, on average, and had them walk on a treadmill for as long as possible. The treadmill was set at about 2.2 miles per hour and a 12-percent grade.
Participants were then randomly assigned to eat a bar of either dark or milk chocolate and re-took the treadmill test two hours later.
The time and distance walked did not change between the first and second sessions for those who ate milk chocolate. Those who ate dark chocolate were able to walk for about 17 seconds longer and 39 feet farther than during their initial walk, however.
The researchers also measured a type of gas in the blood that has been linked to improved blood flow and found it was higher among those who ate dark chocolate, compared to those who ate milk chocolate.
Dr. Thom Rooke, a cardiologist at Mayo Clinic in Rochester, Minnesota, said the effect on walking appeared to be small and may not be particularly noticeable to the average person.
“This is interesting and almost certainly has some scientific validity to it,” he said. “I’m not at all surprised that things in dark chocolate change measurable things in our blood that are capable of making our blood vessels expand or contract. I just don’t think this is going to be a major answer.”
For example, he said eating dark chocolate would also add to the calories people are consuming.
“Any tiny benefit . . . on your walking that you get from chocolate will be offset by weight gain,” said Rooke, who was not involved with the new study.
Loffredo said a future study will need to look at a larger group of people and assess longer-term consumption of dark chocolate. Also, he said the researchers cannot be sure that other components in dark chocolate - besides polyphenols - were responsible for the improvements.
Typically, people diagnosed with PAD are advised to change their behaviors, such as by cutting out smoking and eating a better diet, Rooke said. They’re also told to exercise and may be put on some medications. Surgery to bypass blocked arteries is typically a last resort.
“It’s really an impetus to change your lifestyle, see your physician and clean up your act so to speak,” he said.