Reducing Risk of Heart Attacks Could Be Everyone’s Cup of Tea
The British are known for their love of tea--the average Brit drinks 31/2 cups a day compared with a half-cup daily for Americans--but it is U.S. scientists who are making the most strides in demonstrating tea’s potential to reduce the risk of heart disease.
A study by U.S. researchers published last year in the American Journal of Epidemiology found that people who consume three cups a day could cut their heart attack risk by 11%. Several other studies in the U.S. and elsewhere have also found a link between tea and heart attack prevention.
Scientists believe the beneficial effects of tea are probably due to flavonoids, which are natural plant nutrients in tea. Like certain vitamins and minerals in foods, these flavonoids act as antioxidants, which are believed to limit the effect of “free radicals” in the body and help fight heart disease.
Laboratory work has shown flavonoids help to reduce inflammation and lower the risk of blood clots forming; it is unclear exactly how they produce such effects.
Recent research by Dr. Joseph Vita, a professor at Boston University’s School of Medicine, has shed some light on how these “supernutrients” might work on the linings of blood vessel walls, or endothelium. The endothelium is known to control many aspects of blood vessel activity, including whether the vessels are dilated to allow for maximum blood flow, or are constricted, a condition that can result in high blood pressure, a risk factor in heart disease.
Vita and colleagues examined the effect tea consumption had on the damaged endothelium in 50 patients with heart disease. The patients were measured once, two hours after drinking two cups of black tea, and again after having four cups of black tea every day for four weeks. The tests were then repeated using water instead of tea.
The researchers were surprised to find that tea consumption helped to restore normal function of the endothelium with a marked improvement in dilation of blood vessels; water had no effect. “These results provide an insight into why drinking tea might reduce cardiovascular risk,” Vita said.
Another insight comes from work by Dr. Myron Gross, assistant professor of nutrition and biochemistry at the University of Minnesota, who looked at the effect that flavonoids in tea have on the formation of blood clots. Cells in the blood called platelets have a key role in clotting, providing the bulk of the substances that stick to blood vessel walls and reduce or completely block blood flow.
Preliminary tests by Gross and his team on healthy people indicate that platelet buildup is reduced by drinking six cups of tea a day. In a four-week study, participants were asked to avoid other foods high in flavonoids, including onions, apples, fruit juices, soybean-based products and aspirin.
Gross found that tea drinking reduced platelet clumping by 15%.
While the results are insufficient to warrant clinical claims about the preventive benefits of tea in fighting heart disease, they do support the idea that dietary intervention may play an important role in the prevention of cardiovascular disease. That’s good news because, for one thing, drinking more tea is relatively easy to do, especially because iced tea is as good a source of flavonoids as the hot tea and milkfavored by the British.
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Amanda Ursell, a dietitian and nutritionist, is a London-based freelance journalist. Her column appears twice a month. She can be reached at amanda@ursell.com.
