Over the past two decades, there has been a significant amount of the research conducted around green tea's purported health benefits. The vast majority of that, however, has focused on green tea's link to reduced risk of certain cancers. A recent study may change that focus toward heart benefits; a Greek study has found that green tea may benefit the cardiovascular system.1
Previous studies have associated both green tea and black tea with decreased cardiovascular risk. However, the mechanism behind the decrease is not fully understood. Green Tea contains between 30% and 40% polyphenols while black tea contains 3% to 10% polyphenols; both contain similar amount of caffeine. In an effort to determine if caffeine or the polyphenols provided the benefit, researchers gave 3 different treatments to a group of 14 healthy men over the course of three different occasions. The men had an average age of 30 and were given, 6 grams of green tea, 125 mg of caffeine (the amount of caffeine in 6g of green tea), and plain hot water. Each of the participants received each of the treatments in sequence.
The effects of each of the three treatments was measured at by evaluating changes in brachial artery flow-mediated dilatation (FMD), a measure of the artery's ability to relax. Measurements were taken at baseline, 30, 90, and 120 minutes after consumption. Only the green tea showed a significant change in FMD. At 30 minutes, FMD was increased by 3.69 percent. The lack of benefit from the caffeine indicated that the benefit is not derived from the caffeine alone and must be associated with the green tea polyphenols either by themselves or in combination with caffeine. The researchers concluded, "green tea consumption has an acute beneficial effect on endothelial function, assessed with FMD of the brachial artery, in healthy individuals. This may be involved in the beneficial effect of tea on cardiovascular risk."
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1. Alexopoulos, N., C. Vlachopoulos, et al. (2008). "The acute effect of green tea consumption on endothelial function in healthy individuals." Eur J Cardiovasc Prev Rehabil 15(3): 300-5.
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