Green tea has long been thought to protect against certain types of cancer. There is now an increasing amount of credible scientific evidence that tea can prevent heart disease, cataracts, colon cancer and possibly help women conceive. The preventive effects are thought to be realized through the oxidation process that occurs with processing different types of tea.  The preventative properties of tea are thought to destroy cancer cells. Researchers in Britain and Italy have recently found that extracts of black Assam tea (the equivalent of three to four cups a day) is shown to protect against the effects of a known carcinogen in lab rats (reported in the Tea and Coffee Trade Journal 2001).

Polyphenols are the specific compounds in tea that researchers believe carry the health benefits. These polyphenols, or flavonoids, are increasingly recognized as powerful antioxidants in tea. They are 30 times more potent than Vitamin C and E. Antioxidants eliminate free radicals that damage cells in the body.

Oxidation—which determines if a tea is green, oolong, or black, can alter the types of polyphenols found in tea. Research now shows that it is the entire range of polyphenols found in tea that provides the preventative punch. Polyphenols have been shown to interfere with plaque forming in the heart’s arteries and increase the function of blood vessels. Thus, tea can reduce heart disease and help tea drinkers fare better after a heart attack. One study showed that post heart attack heavy tea drinkers (14 or more cups per week) had a 44% reduced risk of dying of heart attacks compared with non-tea drinkers. This study was important because the participants in both groups were similar in education, income, exercise habits, smoking and drinking habits, so that the positive effects were not the result of an artifact that the healthier people were drinking more tea.

A whole range of polyphenols exists in various teas so it is not only green tea that has positive health benefits, but oolongs and black tea also appear to be extremely beneficial to a person’s health. A study conducted in Taiwan at the National Taiwan University shows that consumption of Puer tea resulted in a significant drop in cholesterol levels. Several studies have found that tea reduces the risk of bladder, stomach, colorectal, prostrate, esophageal and oral cancers. For example, a study done in 2001 at UCLA found that drinking tea reduced the risk of chronic gastritis by half. Other studies found that tea drinking reduced the risk of esophageal cancer and rectal cancer by 60%. Researchers at Rutgers University identified a compound in black tea, called TF-2, which caused decreased colorectal cancer cells in laboratory experiments while normal cells were unaffected.

Tea drinking also appears to improve bone density and strength. Taiwanese researchers found that long-time tea drinkers have stronger bones. Their study showed that hip bone density was 6.2% higher in people who drank tea habitually for 10 years or more. People who drank tea for six to 10 years had a 2.3% higher bone density. A British study published in 2000, also found higher bone density in women who drank at least one cup of tea a day. Tea contains both fluoride and phytoestrogens, which are known to increase bone density.

Recent findings from British research at the University of Newcastle show that green and black tea helps to improve memory and possibly protect against Alzheimer’s disease. Drinking tea regularly inhibits the activity of enzymes in the brain associated with the development of Alzheimer’s disease, while coffee had no significant effect. (Reported in the Tea and Coffee Trade Journal January 2005). A serving of tea contains about 40 milligrams of caffeine, less than half as much as is found in a serving of coffee.

The above excerpt on health effects is taken from Josh Chamberlain’s Master’s Thesis from National Cheng Kung University entitled, Estimation and Forecasting of the Demand for Tea in the United States; July, 2005.