Dark Chocolate May Promote Healthy Blood Flow

Dark chocolate found to prevent white blood cells from sticking to artery walls

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) Dark chocolate lovers may now be able to enjoy their treat even more. A new study suggests that the sweet snack may actually be good for the heart.

Researchers found that an ingredient in dark chocolate prevented white blood cells from sticking to the sides of the arteries. Dark chocolate also allowed the walls of the arteries to more easily expand.

When the arteries, which carry blood to the heart, have thick sides and are rigid, it can lead to heart attack and stroke.

"Ask your doctor how to reduce your risk of heart disease."

The researchers, led by Professor Diederik Esser of the Top Institute Food and Nutrition in Wageningen, the Netherlands, hoped to find out if dark chocolate could be beneficial, but also to determine if dark chocolate containing a high-level of flavanols could prove to be even more beneficial than dark chocolate with a regular amount of flavanols.

Flavanols are naturally occurring anti-oxidants found in cocoa beans and are the ingredient in dark chocolate that is believed to lend it its beneficial effects. Flavanols also give dark chocolate its bitter flavor. 

Forty-one overweight men, aged 45 to 70, were recruited and completed this study. For two periods of four weeks, they were asked to eat 70 grams of chocolate daily.

A regular chocolate bar contains 25 to 50 grams of chocolate. For the first four weeks, they either ate chocolate containing 1,078 mg of flavanols or 259 mg of flavanols. For the final four weeks, they ate chocolate with the opposite amount of flavanols.

The men also were counseled about their eating patterns for the study period so that they did not gain weight.

The participants gave samples of blood and urine so researchers could check how their hearts were faring.

By the end of the study, the subjects had about a 1 percent increase in the level by which their blood vessels expanded. They also had about a 1 percent decrease in their augmentation index. Augmentation index is a ratio of the blood pressure and stiffness of the arteries that is associated with a risk for cardiovascular disease.

Higher levels of flavanol did not seem to confer more of a benefit.

The researchers surmised that the peak vascular effect may be reached with 259 mg of flavanol. However, there is a possibility that there are other ingredients in chocolate which may be beneficial for the heart.

The study's participants seemed to enjoy and were more apt to finish their supply of chocolate when it contained the lower level of flavanol.

"As a chocolate fanatic, I'm thrilled to see another study confirming the benefits of dark chocolate," said Sarah Samaan, MD, cardiologist and physician partner at the Baylor Heart Hospital in Plano, Texas. "While most studies have reported correlations between chocolate consumption and heart health, these researchers really got down to a very detailed analysis of exactly how dark chocolate may be beneficial."

According to Dr. Samaan, "The factors they studied are directly tied to the health of our arteries, and so are very relevant for people who hope to improve their vascular health with diet. Other studies have generally found dark chocolate to be much more beneficial than milk chocolate. This is probably due in large part to important anti-oxidants called flavonols. Since flavonols can also contribute to dark chocolate's bitterness, it's good to know that we don't have to take our chocolate with a spoonful of sugar to make it go down, to paraphrase Mary Poppins. Dark chocolate with a normal amount of flavonols appeared to be just as effective as dark chocolate that was extra high in these nutrients."

This study appears in the March issue of The FASEB Journal.

The study was funded by the Top Institute Food and Nutrition, and the chocolate was provided by Barry Callebaut. The authors declared no conflicts of interest.

Review Date: 
March 4, 2014
Last Updated:
March 12, 2015