Cocoa may be more than just a warm treat during chilly winter months. New research suggests it might ease the pain of walking for people with peripheral artery disease.

PAD is a painful condition that causes narrowing of the arteries, reducing blood flow from the heart to the legs. It affects over 8.5 million people in the U.S. who are 40 years and older. The most common symptoms are pain, tightness, cramping, weakness or other discomfort in leg muscles while walking.

"Few therapies are available for improving walking performance in people with PAD," lead study author Dr. Mary McDermott said in a news release. She is a professor of medicine and preventive medicine at the Feinberg School of Medicine at Northwestern University in Chicago. "In addition to reduced blood flow to the legs, people with peripheral artery disease have been shown to have damaged mitochondria in their calf muscles."

Mitochondria, she said, are known as the powerhouse of the cell – converting food to energy. Better mitochondrial activity is associated with better walking performance. Researchers believe epicatechin, a component of cocoa, may increase mitochondrial activity and muscle health in the calves of patients.

The small trial, published in the American Heart Association's journal Circulation Research, examined 44 people with PAD who were at least 60. Those who drank a beverage containing cocoa three times a day for six months were able to walk up to 42.6 meters farther in a six-minute walking test. That's compared to those who drank the same number and type of beverages without cocoa. Those who consumed cocoa also had increased blood flow to their calves and some improved muscle function.

Researchers found increased mitochondrial activity and increased blood vessel density in those who consumed cocoa. Participants who drank the placebo had a decline of 24.2 meters soon after the final beverage compared to the start of the study.

"If our results are confirmed in a larger trial, these findings suggest that cocoa – a relatively inexpensive, safe and accessible product – could potentially produce significant improvements in calf muscle health, blood flow, and walking performance for PAD patients," McDermott said.

The cocoa used in the research was a natural unsweetened cocoa powder rich in epicatechin, which is found in dark chocolate that is typically made up of more than 85% cacao.

Researchers said the study was limited by its small number of participants, along with an imbalance between the two groups in terms of participants' body mass index, sex and race.

Dr. Naomi Hamburg of Boston University School of Medicine co-authored an editorial about the new study.

"Patients with PAD have difficulty walking that is as bad as people with advanced heart failure," she said. "We will need larger studies to confirm whether cocoa is an effective treatment for PAD, but maybe, someday, if the research supports it, we may be able to write a prescription for chocolate for our patients with PAD."

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