Green tea's reputation for improving human health dates back to antiquity. According to the April 2009 "American Family Physician," after water, green tea is the most frequently consumed beverage in the world, and green tea extracts have become a popular dietary supplement in the United States. The salubrious effects of green tea are supposedly borne in its polyphenol compounds called flavonoids, of which epigallocatechin gallate, or EGCG, is the most extensively studied.
Green Tea Constituents
Besides EGCG, green tea contains a variety of other ingredients, many of which may confer their own health benefits. Green tea's caffeine, theaflavins, theanine and theobromine all exert their own physiologic effects. However, scientists have concentrated their efforts on green tea's polyphenols, which account for 20 to 45 percent of green tea's dry weight, and they have specifically focused on the catechins, which have been attributed with anti-cancer, anti-diabetic, anti-inflammatory and cholesterol-lowering properties.
Metabolic Syndrome, Heart Disease and Green Tea
A 2010 review in the "Journal of the American College of Nutrition" reports that green tea exerts beneficial effects in people who have metabolic syndrome, which is a constellation of traits that include abdominal obesity, high blood pressure, insulin resistance and abnormal blood lipids. Metabolic syndrome has been identified as one of the major risk factors for coronary heart disease, and therapies that ameliorate this syndrome have been shown to reduce your risk for heart disease.
Green Tea, LDL and Arterial Disease
The role of LDL cholesterol in arterial inflammation and atherosclerosis, or hardening of the arteries, is well established. One of the mainstays of therapy for people at risk for heart disease, as well as those who already have it, is a reduction of LDL cholesterol. A 2009 review in the "Current Atherosclerosis Reports" suggested that green tea catechins may lower LDL, and a 2010 study in the "Journal of Applied Physiology" demonstrated that EGCG from green tea decreased the inflammatory damage that LDL causes to the cells that line your arteries.
Considerations
Most of the evidence pointing to the benefits of green tea flavonoids for the prevention of coronary artery disease comes from epidemiological studies, and relatively few human clinical trials have been undertaken. However, the research surrounding EGCG and other green tea polyphenols is promising. If you have heart disease, or if you are at risk, talk to your doctor about whether green tea can be beneficial for you.
References
- "American Family Physician"; Green Tea: Potential Health Benefits; C. Schneider, T. Segre; April 2009
- "Journal of the American College of Nutrition"; Green Tea Supplementation Affects Body Weight, Lipids, and Lipid Peroxidation in Obese Subjects with Metabolic Syndrome; A. Basu, et al.; February 2010
- "Current Atherosclerosis Reports"; Nutritional Supplements and Serum Lipids: Does Anything Work?; M.P. McGowan, S. Proulx; November 2009
- "Journal of Applied Physiology"; EGCG Protects Against Oxidized LDL-Induced Endothelial Dysfunction by Inhibiting LOX-1-Mediated Signaling; H.C. Ou et al.; June 2010
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