Issue 211 Item 15 Dark Chocolate Improves Endothelial Function in Healthy Adults

Flavonoid-rich dark chocolate improves endothelial function and is associated with increased plasma epicatechin concentrations in healthy adults “Dark chocolate derived from the plant Theobroma cacao is a rich source of flavonoids,” write Mary B. Engler, PhD, from the University of California in San Francisco (UCSF), and colleagues. “Cardioprotective effects including antioxidant properties, inhibition of platelet activity, and activation of endothelial nitric oxide synthase have been ascribed to the cocoa flavonoids.”

In the study, investigators randomized 21 healthy volunteer subjects to a daily intake of 46 g of high-flavonoid dark chocolate (n = 11) or dark chocolate with low-flavonoid content (n = 10) for two weeks. The ability of the brachial artery to expand after cuff compression for five minutes was recorded using ultrasound at baseline and at two weeks. Flow-mediated dilation (FMD) of the brachial artery, which corresponds well to that of the coronary arteries, was expressed as the peak change in vessel diameter from baseline.

The mean change in FMD from baseline was significantly different in the high-flavonoid group compared with the low-flavonoid group (P = .02). While the mean decrease in FMD in the low-flavonoid group was not significant (P = .17), the mean increase in FMD in the high-flavonoid group almost achieved significance (P = .05).

“Improvements in endothelial function (the ability of the artery to dilate) are indicative of improved vascular health and a lower risk for heart disease,” Dr. Engler says in a news release. “Arteries that are able to dilate more have increased blood flow, and this is especially important for the heart.”

Epicatechin was absorbed at high levels in the blood. Plasma concentrations at two weeks showed a significant increase from baseline in the high-flavonoid group (25.6 – 204.4 nmol/L; P < .001) but not in the low-flavonoid group, which showed a slight decrease (17.9 - 17. 5 nmol/L; P = .99). “Flow-mediated dilation of the brachial artery is an endothelium-dependent function associated with the release of nitric oxide and possibly endothelium-derived prostanoids,” the authors explain. “It is possible that the elevated plasma epicatechin concentrations in the high-flavonoid group increased endothelium-derived vasodilators and improved endothelial function.” “Our findings suggest a possible cardioprotective effect by flavonoid-rich chocolate, independent of changes in measures of oxidative stress and lipid profiles. J Am Coll Nutr. 2004;23:197-204