Philip J. Goscienski, M.D.
August 2010
Tea is the most popular beverage on the planet and except for water it has been around the longest. Originating in China perhaps as long as 4,000 years ago its health claims have progressed from folklore to prestigious medical journals. Green tea is especially popular as a preventive or cure for conditions that include heart disease, cancer, dementia, osteoporosis, arthritis, obesity and tooth decay. There is medical support for all of these benefits, some marginal but others quite strong. When we add its immune-boosting, stress-reducing and cholesterol-lowering effects it's easy to see why there is so much interest in this inexpensive, non-toxic and non-intoxicating beverage.
The black tea that most of us are familiar with is made from tea leaves that have been exposed to air for at least several hours and then heated. When heating (which inactivates certain enzymes) takes place shortly after harvesting, the result is green tea, rich in flavonoids and other antioxidants that give it the most purported health benefits. Because it has undergone so little processing it has a "grassy" flavor that not everyone appreciates. Black teas such as English Breakfast have deeper flavor and are more popular in Western countries.
Studies among tea drinkers in several countries confirm that it lowers blood pressure as well as heart attack and stroke. Several mechanisms account for the heart benefits of green tea and unlike some of the other claims, extensive studies have been done on humans. The antioxidant flavonoids in tea block the action of free radicals that damage blood vessels. They alter the chemistry of some forms of cholesterol that damage vessel walls. Antioxidants also lower levels of cholesterol and homocysteine, which is associated with coronary artery disease.
The data on cancer is not as compelling and much of it comes from non-human research. The evidence that drinking 2 to 5 cups of green tea a day helps to prevent cancer of the breast and prostate is barely statistically significant but it bolsters the data that comes from animal studies and tissue culture.
Although green tea is a safe, healthy and socially acceptable beverage it is no magic bullet. The mostly Asian populations in which many studies have been done tend to be of normal weight, are more physically active, eat less red meat and more fruits and vegetables. That lifestyle counts for more than a few cups a day of green tea.
Philip J. Goscienski, M.D. is the author of Health Secrets of the Stone Age, Better Life Publishers 2005. Contact him at drphil@stoneagedoc.com.