For Immediate Release:
February 18, 2000

CONTACT: David Ong
(916) 734-9049
daong@ucdavis.edu

COMPOUNDS IN COCOA FOUND BENEFICIAL TO ARTERIES, STUDY FINDS

(WASHINGTON, D.C.) - Cocoa contains compounds that cause blood vessels to dilate, or relax, indicating that these substances may offer protection against the condition commonly known as "hardening of the arteries," according to a study by researchers at the UC Davis School of Medicine and Medical Center.

The study's lead author, UC Davis cardiologist C. Tissa Kappagoda, will present the study on Saturday, February 19, at 9 a.m., at the annual American Association for the Advancement of Science Conference in Washington, D.C. Kappagoda also will participate in a news briefing on "The Healthy Side of Eating Chocolate" on Friday, February 18 at 2 p.m. in the Wilson room of the Marriott Wardman Hotel.

Coronary atherosclerosis is the accumulation of cholesterol, fats, calcium and other elements in the walls of arteries. The buildup restricts the flow of blood to heart muscle, and affected arteries are prone to blood clots, small hemorrhages and spasms, which can lead to heart attacks.

Previous studies have indicated that flavonoids, a group of chemical compounds found in plants, can dilate blood vessels, thus maintaining their capacity to carry blood. Among other properties, flavonoids are antioxidants, which neutralize dangerous molecules produced by the body that can lead to cancer. The ability of flavonoids to relax arteries has been widely attributed to the compounds' antioxidant qualities.

Using different kinds of defatted cocoa powder extracts on laboratory animals, Kappagoda found that certain flavonoids in cocoa can stimulate the relaxation of blood vessels and offer possible protection against dangerous fatty buildups. However, the study also found that these effects are unrelated to the flavonoids' antioxidant properties.

The study consisted of three groups of in-vitro investigations. The first set of experiments used three varieties of cocoa extracts on rabbit aorta segments. One of the extracts had no effect, while the other two caused a relaxation of the segments. Additional tests using other powerful antioxidant compounds had no effect, suggesting that the dilation produced by the effective cocoa extracts was not associated with their antioxidant activity.

When the aorta segments were incubated for 30 minutes with the two effective cocoa extracts, the relaxation effect was diminished. The effect was partially restored when the segments were exposed to arginine for 30 minutes following their incubation with the cocoa flavonoids. Arginine is an amino acid in the endothelium, the cells lining the arteries that cause dilation to occur by generating nitric oxide. The study suggests that long-term exposure to flavonoids might deplete arginine from the endothelium, hindering its ability to produce nitric oxide and, consequently, its capacity to relax blood vessels.

In the second set of studies, the arteries of rabbits fed a diet of standard chow plus cholesterol had a diminished capacity for dilation. However, the arteries of rabbits fed the same diet plus defatted cocoa extract exhibited no such impairment, which suggests that the flavonoids may preserve the vessels' ability to dilate.

In the final set of experiments, one kind of cocoa extract induced the development of blood vessels in the membrane of a chicken fetus. The extract produced blood vessels that were larger and had greater diameters than those in a membrane that had new blood vessels developed by a growth factor. The results suggest that the protective effects of certain cocoa flavonoids on blood vessels is related to the compounds' influence on the development of new blood vessels, and will serve as the basis for future research in that area.

Kappagoda plans further research to seek the biochemical mechanisms by which flavonoids exert their effects. Their identification could be an important step toward developing medications for the prevention and treatment of cardiovascular diseases.

Copies of all news releases from UC Davis Health System are available on the web at http://news.ucdmc.ucdavis.edu

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