Numerous studies claim that in moderation, dark chocolate is good for our health. Now, a new study published in the Journal of the American Heart Association adds to the evidence, suggesting that it may help increase walking distance for people with peripheral artery disease.
Peripheral artery disease (PAD) affects more than 8 million people in the US. It is characterized by narrowing of the peripheral arteries and reduced blood flow to the stomach, arms, head and most commonly, the legs.
Cramping, pain or tiredness in the leg or hip muscles during walking or climbing stairs are the most common symptoms of PAD, meaning many patients are unable to walk long distances without stopping to rest.
Past research has indicated that dark chocolate offers cardiovascular benefits. Earlier this year, Medical News Today reported on a study published in The FASEB Journal, which revealed that it may reduce the risk of atherosclerosis - thickening and hardening of the arteries.
For this study, the research team - including Dr. Lorenzo Loffredo of the Sapienza University of Rome in Italy - wanted to see whether dark chocolate could improve mobility in people with PAD.
Polyphenols in dark chocolate may explain improved walking ability
Dr. Loffredo and colleagues recruited 20 participants - 14 men and six women - who had PAD.
The participants were required to provide blood samples and undergo a series of walking tests on a treadmill over 2 days.
Researchers found that after eating 40 g of dark chocolate, PAD patients were able to walk further and for longer.
On the first day, subjects were asked to walk for as long as they could on a treadmill while the researchers measured their walking time and distance. They were then given 40 g of dark chocolate to eat (approximately the size of standard chocolate bar), and 2 hours later they walked on the treadmill again.
The same regime was repeated on the second day, but participants were given 40 g of milk chocolate instead of dark chocolate.
Results of the study revealed that after the participants ate the dark chocolate, they were able to walk for an average of 17 seconds longer and almost 12 meters (39 feet) farther than they did before eating the dark chocolate. However, no increased walking time or distance was found after they ate the milk chocolate.
The researchers hypothesize that the increased walking time and distance after consumption of dark chocolate may have something to do with its richness in polyphenols - a type of antioxidant. They note that the dark chocolate had cocoa content of 85%, making it much richer in polyphenols than the milk chocolate, which only had a 35% cocoa content.
The team says that after the participants had eaten the dark chocolate, they had higher levels of nitric oxide in their blood - associated with improved blood flow - and had reduced biochemical signs of oxidative stress, which the researchers say may have dilated the peripheral arteries and improved walking ability.
Based on these findings, senior study author Dr. Francesco Violi, also of the Sapienza University of Rome, says "polyphenol-rich nutrients could represent a new therapeutic strategy to counteract cardiovascular complications."
The researchers admit that their findings are subject to limitations. For example, they did not have a placebo group in the study and patients were aware of the type of chocolate they were being given, which they say could have affected the results.
They conclude that further research with a larger group of PAD patients is warranted to confirm the results.
Findings 'should be interpreted with caution'
A spokesperson for the American Heart Association (AHA), Dr. Mark Creager, warns people should be cautious of the team's findings:
"Other investigations have shown that polyphenols including those in dark chocolate may improve blood vessel function. But this study is extremely preliminary and I think everyone needs to be cautious when interpreting the findings.
We know from other studies of antioxidants - vitamin C and E for example - that these interventions have not gone on to show improvement in cardiovascular health."
The AHA note that there are other foods rich in polyphenols that are a healthier alternative to chocolate, such as dried peppermint, capers and hazelnuts.
Other studies have suggested that chocolate may also yield benefits for other health conditions. Earlier this year, Medical News Today reported on a study suggesting that chocolate could prevent obesity and diabetes, while other research found that hot chocolate may prevent memory decline.
Our Knowledge Center article on the health benefits of chocolate reveals some of the other ways the food may be good for you.