It originates from the same plant as black tea, but the leaves are prepared differently. Unlike black tea, the leaves are steamed to prevent oxidation of the active agents. Green tea is very popular in China, Japan, and India. People generally drink 3 cups per day to promote health. The taste of green tea is very different from black tea, which has limited its popularity in the western world. It is available in grocery stores and sold in tea bags or as dried herb.
There are a number of retrospective studies performed in Japan and China that indicate individuals who drink green tea have a lower incidence of cancer. There are also claims that those who develop cancer tend to do so at an older age. Green tea has been shown to inhibit tumor growth in test tubes in some studies. However, there are no prospective randomized studies proving its efficacy in humans.
Because green tea originates from the same plant as black tea, caffeine is contained within the tea. Side effects are related to the caffeine and consist of insomnia, palpitations, nervousness, and headaches. Those patients who suffer from migraine headaches, irregular heartbeats, and anxiety disorders should avoid large amounts of any beverage with caffeine. Pregnant or nursing women should also avoid large amounts of caffeine.
If you are considering using an alternative or complementary treatment such as green tea, always discuss it with your doctor. There are numerous studies currently evaluating the use of green tea for the prevention of cancer. Until these studies are completed, final recommendation regarding the use of green tea cannot be made.