Research revealed that green tea prevents the formation of new plaque in the arteries but does not remove pre-existing plaque according to an article in the May 25 2004 issue of the American Heart Association journal Circulation.
A team at Cedars-Sinai Medical Center Atherosclerosis Research Center fed a high cholesterol diet to mice bred to rapidly develop atherosclerotic plaque. Injury to the right carotid artery was carried out at twenty-eight weeks of age to induce the formation of new plaque so that the researchers could examine the effect of a purified form of the green tea catechin epigallocatechin-3-gallate (EGCG) on both new and established plaque. The compound was injected five days per week following arterial injury, and the arteries of mice who received EGCG as well as control groups who did not receive the compound were examined after three, twenty-one and forty-two days.
Mice treated with EGCG were found to have significantly reduced new plaque formation at the injury site compared to the control mice, but there was no benefit for the compound on established plaque. Lead author Kuang-Yuh Chyu , MD, PhD, of UCLA, explained, "Most animal experiments evaluating the effects of antioxidants are started when the animals are young, while randomized clinical trials typically enroll adult patients with varying stages of plaques. This discrepancy supports speculation that antioxidant treatment affects early but not later stages of plaque development. EGCG treatment was started late, when atherosclerotic lesions in the aortic sinus were already at an advanced stage. Our observations that EGCG reduced the progression of evolving carotid plaques but had no effect on the mature plaques in the aorta reinforce the theory that intervention is effective in early but not late stages of atherosclerotic development. It appears that antioxidant therapy would have therapeutic benefits only if initiated during a critical window very early in the formation of plaque."
Circulation, May 25, 2004