Tea is the second most consumed beverage in the world after water. Its origins are in Southeast Asia, where tea has been consumed for thousands of years. All teas come from the same species of plant, Camellia sinensis. The differences lie in the way the teas are processed through oxidation (also called fermentation). Unlike black and oolong teas, green tea leaves are steamed to prevent oxidation and, therefore, retain higher catechin polyphenol levels such as epigallocatechin gallate (ECGC).

In China, tea has long been part of cultural practices and incorporated within traditional Chinese medicine. Recently, there has been a dramatic increase in scientific research examining the health benefits of green tea, including epidemiological studies, preclinical research and clinical trials.  

Of particular interest is the examination of ECGC -- a powerful antioxidant that is thought to be one of the main components of the health benefits of tea. Several epidemiologic studies in East Asia have found associations between green tea and lower cancer incidence. For example, in 1994 the Journal of the National Cancer Institute published the results of a study indicating that drinking green tea reduced the risk of esophageal cancer in Chinese men and women by nearly 60%.  

The research on green tea
In a recent study, MD Anderson researchers examined the effects of green tea extract on people with a precancerous condition called oral leukoplakia. Results were encouraging, showing less progression towards development of cancer in more than half of those who took the extract.