Lee Swanson Research Update

Green Tea Extract May Boost Blood Vessel Health

June 2007

Green tea extract may increase blood flow in people with coronary artery disease (CAD) by improving endothelial function in the arteries, according to a study published in the Journal of the American College of Nutrition.

Epigallocatechin gallate (EGCG), the main extract from green tea, "acutely improves endothelial function in humans with coronary artery disease, and may account for a portion of the beneficial effects of flavonoid-rich food on endothelial function," wrote the authors of the study.

The researchers, led by Michael Widlansky from Boston University School of Medicine, state that epidemiological studies have demonstrated the benefits of dietary flavonoid intake. These may be related to improved endothelial function.

Widlansky and co-workers recruited 42 subjects to take part in the double blind, placebo-controlled, crossover design study. Subjects were randomly assigned to receive either an EGCG supplement or a placebo.

Blood flow in the arm, referred to as brachial artery flow-mediated dilation (FMD), was measured by vascular ultrasound at baseline and again two hours after an initial 300 mg dose of EGCG or placebo, and after two weeks of supplementation with two 150 mg doses of EGCG per day or placebo. Before being crossed over to the other intervention, the subjects underwent a one-week washout period.

Supplementation with the green tea extract was found to improve FMD from 7.1 to 8.6 percent two hours after the initial 300 mg dose. The advantage dropped off, however, 14 hours after the two-week regimen ended.

Journal of the American College of Nutrition 26(2):95-102, 2007

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