The team measured the artery's "flow-mediated dilation" using ultrasound to obtain the brachial artery's diameter immediately after deflating a blood pressure cuff that had been inflated for five minutes on study participants' forearms. "This measurement actually gives us a "videoclip" of an individual's vascular health, and can be helpful in determining whether one is at risk for heart disease," says Engler. The induced increase in blood flow after the cuff is deflated causes release of many dilator substances, such as nitric oxide and prostanoids, which relax, the artery. Flow-mediated dilation is expressed as the percentage maximum change in vessel diameter from baseline.
In the high-flavonoid group, flow-mediated dilation increased from an initial 10.2 percent at the beginning of the study to 11.5 percent at the end of the study, while in the low-flavonoid group dilation decreased from 10.7 percent at the beginning of the study to 9.74 percent at the end of the study. The mean increase in flow-mediated dilation between the two groups showed a statistically significant difference, says Engler.
"Improvements in endothelial function [the ability of the artery to dilate] are indicative of improved vascular health and a lower risk for heart disease," Engler says. "Arteries that are able to dilate more have increased blood flow, and this is especially important for the heart."
Engler and her group also found that concentrations of the cocoa flavonoid epicatechin soared in blood samples taken from the group that received the high-flavonoid chocolate, rising from a baseline of 25.6 nmol/L to 204.4 nmol/L. In the group that received t
Contact: Joan Aragone
University of California - San Francisco