Dr. Joseph Vita, M.D.
Institution: Boston University School of Medicine
Black tea tames artery disease
A new study finds a strong link between drinking black tea and arterial health in people who have heart disease. "The study demonstrated that drinking black tea reverses endothelial dysfunction. Endothelial dysfunction is believed to contribute importantly to the development of cardiovascular disease," said Joseph Vita, M.D., a professor of medicine at Boston University School of Medicine and senior author of the study.
"We've shown that black tea helps reverse this dysfunction, and this finding may help explain prior studies that found fewer cardiac events in tea drinkers."
The vascular endothelium, which forms the inner lining of cells in all blood vessels, produces substances that regulate the diameter of the blood vessel. It responds to minute-to-minute changes in the body's oxygen and blood flow needs, by causing blood vessels to expand (dilate) or contract. The vessels expand when the need for blood flow is higher, as occurs during exercise, and the vessels return to original size when the individual is at rest. The healthy endothelium also inhibits the formation of blood clots and the development of inflammation in the vessel wall. All of these functions may be impaired in individuals with atherosclerosis.
Researchers believe that endothelial dysfunction is a contributing cause of heart attack and stroke. Study participants were Boston Medical Center patients with either a history of revascularization (a procedure to re-open blocked arteries) or at least one coronary artery with greater than 70 percent blockage. Participants maintained their usual diet, but excluded red wine and other tea consumption during the eight-week study. Half the group drank tea for four weeks and half drank water, then they switched to the other beverage for another four weeks.
"No previous study has examined the effects of tea on endothelium. The present study provides a plausible biological mechanism in humans to explain the inverse relationship between black tea and cardiovascular disease," Vita said. "Our findings fit well with the growing appreciation that diet and lifestyle modifications are important approaches to the prevention and treatment of atherosclerosis."
The exact tea component responsible for the benefit is unknown, but researchers theorize that antioxidants in tea called flavonoids may have been responsible. Previous studies have shown that black tea and other foods rich in flavonoids (such as purple grape juice and red wine) prevent the oxidation of low-density lipoproteins (LDL), the so-called "bad" cholesterol that leads to the formation of plaque in artery walls. Although very high concentrations of tea flavonoids are needed to protect LDL, the lower concentrations achieved in this study may have had a direct effect on the endothelium.
The study was funded by a grant from the North America Tea Trade Research Association. Dr. Vita's efforts are also funded by a National Center Established Investigator Grant from the American Heart Association. He previously held a National Center Grant-in-Aid and a New England Affiliate Postdoctoral Fellowship.
"I couldn't have done it without the AHA," Vita said.