The possible disease-prevention benefits of green tea have made headlines for years. Many studies have drawn an association between green tea and stronger immune systems as well as the prevention or reversal of common chronic illnesses. A pair of new studies may explain how the brew can play a role in the prevention of breast and prostate cancer.
Spotlight on green tea
At the 11th Annual International Conference on Frontiers in Cancer Prevention Research held in Anaheim, Calif., on Oct. 18, new insight on the cancer prevention qualities of green tea was presented with two different studies.
Researchers from University of California Los Angeles found that drinking green tea may reduce prostate cancer risk by reducing levels of prostate-specific antigen as wells as inflammation associated with prostate cancer growth. A study conducted at Columbia University Medical Center in New York found that antioxidants in green tea called polyphenols interfered with two proteins called growth factors that promote breast tumor cell growth and migration.
Green tea lowers PSA levels
In the UCLA green tea prostate cancer study, 79 men with prostate cancer waiting for surgery were separated into groups either drinking six cups of green tea or plain water a day. Urine and blood samples were taken at the beginning of the trial. After surgery, researchers examined samples of prostate tissue.
Compared to those drinking water, the green tea group had lower levels of a protein linked to prostate tumor growth called prostate-specific antigen (PSA). PSA levels were lower in the blood as well as in the biopsied prostate tissue. The green tea drinkers also had lower levels of a tell-tale signal, or marker, of inflammation called nuclear factor kappa B. A marker in the urine of DNA damage caused by oxidation was also lower in the men drinking green tea.
Green tea extract lowers growth factors
In the Columbia University study, participants were given a commercial green tea extract instead of brewed green tea. Researchers separated 40 women already treated for breast cancer into groups taking green tea extract twice a day or a placebo for six months. Those on the green tea extract had significantly lower levels of tumor growth factors after two months.
One goal of the Columbia study was to establish a safe, effective dose of the green tea extract, Polyphenon E, for breast cancer prevention. Women in the study took the equivalent of eight to 24 cups of brewed green tea.
The Japanese example
Either brewed or in pill form, the polyphenols in green tea may be particularly effective for prostate cancer because it progresses so slowly. A diet intervention such as green tea could slow it further.
Neither team of researchers said their evidence was conclusive enough to recommend drinking copious amounts of green tea. But according to the World Health Organization, in Japan, where people drink a lot of green tea, prostate and breast cancer rates are three times lower than in the U.S.