The next time you're offered a choice between Earl Grey and green tea, you might want to go green.
A new study shows that the beverage, which is more popular in Eastern cultures, can protect heart arteries by keeping them flexible and relaxed, and therefore better able to withstand the ups and downs of constant changes in blood pressure. Led by Dr. Nikolaos Alexopoulos of Athens Medical School in Greece, the researchers found that among 14 subjects, those who drank green tea showed greater dilation of their heart arteries on ultrasound 30 min. later than those drinking either diluted caffeine or hot water. That's because, the scientists speculate, green tea works on the lining of blood vessels, helping cells there to secrete the substances needed to relax the vessels and allow blood to flow more freely. It's the flavonoids in the tea, which work as antioxidants and help prevent inflammation in body tissue, that keep the vessels pliable. These substances may also protect against the formation of clots, which are the primary cause of heart attacks. "We found very promptly [that] after drinking green tea, there was a protective effect on the endothelium," says Dr. Charalambos Vlachopoulos, a cardiologist and one of the authors of the study.
All it took, says Vlachopoulos, was 6 g of green tea, which amounts to 3 to 4 cups. To make sure the dilation effect was not due to the small amounts of caffeine found in green tea, the group compared the arterial sizes in the green-tea drinkers with those consuming a diluted caffeine beverage and found no change in arterial size in the caffeine drinkers. Even more intriguing, the beneficial effect seems to be long-lasting and cumulative. When the doctors measured the green-tea drinkers' arteries two weeks after daily consumption of the beverage, they found that their vessels were more dilated than they had been at the beginning of the study. "It's something that needs to be investigated, but we think that if someone takes green tea for one or two months, the beneficial effect will be even greater," says Vlachopoulos.
But experts caution that one study isn't enough to catapult green tea to wonder-drink status. Dr. Robert Eckel, a professor at the University of Colorado, Denver, and past president of the American Heart Association, notes that endothelial function is affected by a number of factors, including large doses of vitamins E and C. "Green-tea consumption may have beneficial effects on the arteries, but we should stop short of translating that into a recommendation that everybody should be drinking green tea because it's been proven to reduce heart attacks and strokes," he says. He acknowledges, however, that early studies hint that green tea may be a good addition to a heart-healthy diet. The American Heart Association does not yet include the beverage in its dietary recommendations, but more studies like this one may change that. In the meantime, if you're drinking tea, it might not be such a bad idea to go green.