(NaturalNews) Drinking green tea may help prevent heart disease and stroke, according to a study conducted by researchers from the Athens Medical School in Greece and published in the"A couple of cups a day would probably be a good dose for people," researcher Charalambos Vlachopoulos said. "This is the first study to show these effects for green tea."Prior research has indicated that black tea can improve cardiovascular health, leading researchers suspect that green tea might even more effective. Many of the beneficial health effects of tea are attributed to its high content of antioxidant polyphenols, especially flavonoids. Most of these polyphenols are destroyed, however, by the fermentation process that makes tea black. This is why green tea has a water-extractable polyphenol content of between 30 and 40 percent, while the content in black tea is only 3 to 10 percent.Oolong tea, which is partially fermented, has a polyphenol content between that of green and black tea.In the current study, researchers had 14 volunteers drink three different beverages, on three separate occasions: 6 grams of green tea, 125 milligrams of caffeine (the amount found in 6 grams of green tea) and a cup of hot water. They measured the flow-mediated dilation (FMD) of the participants' blood vessels at 30, 90 and 120 minutes after consumption.FMD is a widely used measure of blood vessel health.The participants' FMD improved by an average of 3.9 percent within 30 minutes of drinking green tea . It did not change at all in those who drank either the caffeine or hot water."Green tea is consumed less in the Western world than black tea, but it could be more beneficial because of the way it seems to improve [circulatory] function," Vlachopoulos said.He also noted that a number of studies have linked green tea to various cancer-fighting effects.Sources for this story include: www.reuters.com;