Shen Nung, the second emperor of China, is said to have discovered tea as early as 2737 BC when tea leaves blew into his cup of hot water. Over three thousand years later, during the Tang Dynasty in China, tea culture flourished and tea entered people's daily lives as a major commodity. Since then tea has served as a social outlet, a symbol of status, a battlefield sedative, and a stimulant to enhance meditation and prayer.
Tea has also long been thought to have powerful healing properties, and is reputed to be helpful with rheumatoid arthritis, high cholesterol, heart disease, infection, and impaired immunity. Recent laboratory research actually suggests drinking tea may slow or even prevent the development of cancer. Although studies in humans are inconclusive, scientists continue to explore the healing properties of tea, and the relationship of tea drinking with the prevention of cancer.
All real "tea" is derived from leaves of the evergreen plant, Camellia sinensis. The health benefits of tea are related to a number of compounds derived from this plant known as flavonoids, which are released during the steeping process (preparing tea in hot water). While black, red, and white teas undergo different levels of fermentation and oxidation, green tea is steamed quickly from fresh leaves. As the least processed true tea, green tea has the highest concentrations of flavonoids, and is the tea most often linked to health benefits covered in the news today. Of note, "herbal tea" is a mixture of herbs, flowers, roots, and spices, and is actually a "tisane" rather than a true tea. Tisanes, along with instant iced tea, lack the health-promoting properties attributed to flavonoids.
Catechins, a type of flavonoid highly concentrated in green tea, have the reported benefits of reducing body fat, cholesterol levels, and blood pressure. Catechins function as antioxidants, substances that neutralize harmful chemicals in the body called "free radicals". Antioxidants occur naturally in many foods, especially fruits and vegetables, and are known to balance and negate the harmful effects of free radicals. Free radicals, which are constantly produced in the body, damage cellular DNA, often leading to malignant change. Studies have demonstrated that, as antioxidants, catechins repair cellular changes that would otherwise lead to the development of cancer, and that catechins suppress key molecules responsible for the development of smoking-related lung cancer. Despite the promising early laboratory research, however, studies exploring the relationship between green tea and cancer in humans have been inconclusive.
While some epidemiological studies claim beneficial effects of tea, others do not. In mice studies, tumors of liver, skin and stomach cancer have been shown to decrease in size in mice that were fed green and black tea. Additional studies in Beijing, China have shown green tea is protective against esophageal cancer, stomach cancer, and precancerous oral lesions. Other studies, including one from the Netherlands investigating stomach, colorectal, lung, and breast cancer, found no significant anti-cancer benefit from green tea. Research at the National Cancer Institute (NCI) has found limited anti-cancer benefit for prostate cancer patients.
Future studies should provide more answers on the relationship between tea and cancer. For more information about NCI-sponsored studies on green tea, go to http://cancer.gov/clinical_trials/. While the jury is out on its anti-cancer properties, tea drinking is known to have numerous other health benefits. Tea contains about half of the amount of caffeine found in coffee; it provides a general calming effect; and it is a great way to maintain hydration. Remember to brew your tea with filtered or bottled spring water with a natural mineral content to maximize good flavor, use a steeping time of 3-5 minutes to release the most flavonoids, and relax and enjoy your cup of tea.
Published On: January 17, 2008