According to research, a chemical found in green tea but not black tea helps stop the growth of cancer cells. A single cup of green tea contains huge, yet nontoxic amounts of the chemical, one of a class known as cathechins, which slows or even stops an enzyme that cancer cells need to grow and spread. Although it is less effective in stopping cancer than medical drugs, the chemical, epigallocathechin-3 gallate, or EGCG, can be taken in much higher doses without making someone ill, and so could play an important role in fighting cancer.
Black tea does not confer the same advantages, because the brewing process oxidises the cathechins, destroying their positive effects, says a team of US scientists. The work at the Medical College of Ohio and the University of Toledo is published today in the science journal Nature.
Tests found that it binds to an enzyme called urokinase, preventing the enzyme from functioning. Normally, cancer cells depend on the action of urokinase to split and grow. "Amiloride is administered in a maximum dose of 20mg per day, whereas a single cup of tea contains 150 mg [of] EGCG and some tea lovers consume up to 10 cups a day." they write. Such high levels "could reduce incidence of cancer in humans, or the size of cancers already formed".