Green tea, made from unfermented leaves of Camellia sinensis -- a plant that is native to China -- is a staple in the diets of millions of people throughout the world. Green tea is highly valued for its culinary and purported medicinal effects, some of which have been substantiated by scientific research.
Endothelial Damage
Green tea protects smokers from endothelial damage, according to research conducted at the Department of Cardiovascular, Respirator, and Geriatric Medicine, Kyushu University Hospital in Japan. In the study, male smokers drank a beverage containing either 80 mg or 580 mg of green tea catechins -- active components in green tea -- per day for two weeks. Blood flow in the participants' forearms showed improvement within two hours in the high-dose group. The beneficial effects continued throughout the study period in the high-dose group. Additionally, levels of tissue-degrading molecules decreased in the high-dose group. No benefits were observed in the low-dose group in this study, published in the 2010 issue of the journal "Internal Medicine."
Atherosclerosis
Antioxidants in green tea may prevent atherosclerosis by lowering cholesterol and triglyceride levels, according to the University of Maryland Medical Center. However, its mechanism is not fully understood as of 2011. Your risk of heart attack can decrease by as much as 11 percent if you drink three cups of tea per day. Green tea also raises your levels of high-density lipoprotein, HDL, the good form of cholesterol and lowers levels of low-density LDL, the bad form of cholesterol, possibly by blocking intestinal absorption.
Multiple Effects
Researchers at the Department of Human Nutrition, Foods and Exercise, College of Agriculture and Life Sciences at Virginia Polytechnic Institute reported that green tea exerts its cardiovascular benefits in multiple ways. Green tea provides antioxidant, blood pressure-lowering and anti-inflammatory benefits. Compounds in green tea also inhibit thickening of artery walls, inhibit blood clots and lower cholesterol levels. Several methods of antioxidant activity have been identified in green tea compounds, including scavenging free radicals, binding to metals, inhibiting pro-oxidant enzymes and promoting antioxidant enzymes. Catechins in green tea lower blood pressure by activating nitric oxide -- a blood pressure-lowering compound -- within blood vessel walls. Catechins also inhibit platelets from sticking together to form blood clots. The study was published in the 2008 issue of the journal "Current Medicinal Chemistry."
Cholesterol
In short-term studies, green tea has been shown to prevent cholesterol levels from rising after meals, according to a study conducted at the Department of Nutritional Sciences at Oklahoma State University. Studies of long-term consumption of green tea in some Southeast Asian countries show a decreased risk of cardiovascular disease. The researchers note that there is a need for further study to evaluate the safety of green tea and its potential role in weight reduction and other aspects of health that increase risk of cardiovascular disease. The study appeared in the August 2007 issue of the journal "Nutrition Reviews."
References
- "Internal Medicine"; Green Tea Catechins Improve Human Forearm Vascular Function and Have Potent Anti-inflammatory and Anti-apoptotic Effects in Smokers; J. Oyama, et al.; 2010
- University Of Maryland Medical Center: Green Tea
- "Current Medicinal Chemistry"; Green Tea Catechins and Cardiovascular Health: an Update; P. Babu, et al.; 2008
- "Nutrition Reviews"; Mechanisms and Effects of Green Tea on Cardiovascular Health; A. Basu, et al.; August 2007
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