Tea drinking is an ancient custom with origins in 2737 BC China. Reputedly, the Emperor Shen Nung, known as the great “divine healer,” first sampled tea after a gust of wind carried a few stray leaves of the Camellia sinensis plant to an open pot of boiling water. Today, approximately 3,000 varieties of tea are made from this single plant, at least 300 in Chine alone. In the west, the U.S. is second only to Great Britain in tea consumption, brewing more than 2.2 billion gallons each year – enough to fill more than 160,000 swimming pools. But, tea offers more benefits than being a soothing beverage to be served at social gatherings, or to ward off the chill of a winter’s night. There is mounting evidence to suggest that drinking tea may also reduce the risks of developing cardiovascular disease and many forms of cancer.
There are three types of tea manufactured: green tea, black tea (often labeled as pekoe or orange pekoe), and oolong tea. The difference between them lies in how the leaves are processed. Black tea is by far the most popular, comprising 77% of the world’s tea production, and is the result of allowing the leaves to ferment before drying. Oolong tea production involves partial fermentation, while green tea is not fermented at all.
Tea leaves are an abundant source of flavonoids (sometimes called bioflavonoids), a group of compounds with antioxidant properties that lend many plants their color. Of specific interest are the flavonoids catechins and flavonols which prevent the synthesis of peroxides and free radicals, agents that can invade cell membranes and damage genetic material. Certain chemicals found in the molecular structure of these beneficial flavonoids, collectively known as phenolic groups, bind with peroxides and free radicals to annul their ability to cause damage.
The fermentation process activates the oxidation of catechins to convert them into the secondary flavonoids theraflavin and thearubigin, also highly oxidant and responsible for the rich color and flavor of black and oolong teas. Green tea, on the other hand, is manufactured without fermentation and the original catechin structure is preserved. The most significant catechin present in tea, epigallocatechin gallate (EGCG) is much more abundant in green tea, with a single cup yielding from 40 to 90 milligrams.
A New Look at an Old Tradition
For more than two decades, researchers have been trying to understand the role of tea, particularly green tea, in the prevention of certain diseases. In September of last year, scientists from around the world gathered in Washington, DC for the Second International Scientific Symposium on Tea & Human Health to present some promising new findings that suggest the antioxidant qualities of tea may rival that of broccoli, carrots and even vitamin E.
Rutgers University has conducted a series of studies on the effect of both green and black tea on skin cancer in recent years. In one study, skin tumors were spawned in mice by exposing them to ultraviolet-B light and a cancer-causing chemical known as dimethylbenzanthracene. Of the tea-treated group, 65 to 93% evidenced fewer carcinomas, and 60 to 90% had less pre-cancerous skin lesions. A very recent trial study at the Chinese Academy of Preventative Medicine in Beijing involved oral and topical applications of black and green tea on subjects diagnosed with pre-cancerous oral lesions. The control group displayed a significant decrease in cell growth after six months of treatment.
Other recent studies to examine the cancer-inhibiting properties of tea have been carried out by the Mayo Clinic. Researchers have found that EGCG deters cell proliferation in human prostate cancer cells. Several studies using animal models, demonstrate that EGCG inhibits the growth of existing tumors, reduces low-density lipoprotein (LDL) levels, and in one in vitro trial, offered antioxidant protection more than 200 times that of vitamin E.
Japanese studies indicates that supplementation with EGCG may help to prevent heart disease. Since the 1980s, studies have concentrated on the effect of catechin polyphenols, including EGCG, on blood cholesterol levels. Rats, fed a special diet designed to induce high cholesterol levels, showed reduced blood cholesterol and LDL concentration in addition to lower blood pressure when their diets were supplemented with tea catechins.
Numerous other studies show a correlation between the protective agents found in tea and a reduced risk associated with cancers involving the lungs, esophagus, prostate, colon and stomach.
Drink to Your Health
While there is still much to learn, western researchers are beginning to form the same conclusion that Chinese medicine has subscribed to for centuries – tea can help to keep you healthy. There may even come a time when tea extract preparations will be as common in the pantry as are free radical scavenging vitamin supplements. In the mean time, drink up. The research suggests that in addition to a low fat diet rich in whole foods, fruits and vegetables, as little as an average of five cups of tea each day may actually help to keep heart disease and certain types of cancer at bay.