Dark chocolate found to enhance blood flow to legs

Older people who have trouble getting around because of poor blood flow to their legs may be able to walk a little longer and farther after eating dark chocolate, according to a new small Italian study.

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.

Improved performance

He and his colleagues write in the Journal of the American Heart Association that compounds known as 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 aged 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.

More than just flavanols

Another recent study, conducted by researchers from Wageningen University in the Netherlands and published in the FASEB Journal in February 2014, suggests that it may be more than just flavanols behind chocolate’s benefits for blood vessel health.

Researchers assigned 44 overweight men between the ages of 45 and 70 to eat 70 g per day of either normal dark chocolate or dark chocolate specially processed to have an especially high flavanol content. The cocoa content of the two chocolates was similar. The men were directed to maintain their weights by not eating other high-calorie foods during the study.

After two weeks, the researchers found that both groups showed equal increases in measures of blood vessel health, including flow-mediated dilation (FMD), augmentation index (AIX), reduced leukocyte (white blood cell) count, decreased plasma sICAM1 and sICAM3 and reduced expression leukocyte adhesion markers. These changes indicate that white blood cells were not sticking to blood vessel walls as much, and that the arteries were more flexible and less hardened.

Other studies have linked dark chocolate consumption to a lowered risk of stroke, and to less age-related memory loss.

Small effect

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.