SAN FRANCISCORetrospective and laboratory studies have suggested that green tea might be useful for both the prevention and treatment of cancer. Two presentations at the 93rd Annual Meeting of the American Association for Cancer Research, however, showed conflicting results on the effectiveness of this beverage as an anticarcinogenic agent.
While one study showed that drinking green tea is linked to a dramatically reduced risk of developing certain gastrointestinal (GI) cancers, another study found that drinking green tea did not have a therapeutic effect in men with advanced prostate cancer.
In the epidemiological study, which used data from the Shanghai Cohort, researchers found that men who frequently drank green tea were much less likely to develop gastric and esophageal cancer, compared with men who drank this beverage infrequently (abstract 2354).
The Shanghai Cohort consists of 18,244 men between the ages of 45 and 64 who had no history of having cancer at study entry and who live in Shanghai, China. Each subject was interviewed and provided a blood and urine sample at study entry. The group has been followed for up to 12 years.
The Shanghai study compared baseline levels of two polyphenols found in green tea, epigallocatechin (EGC) and epicatechin (EC), and their metabolites in urine samples provided by 190 subjects who later developed gastric cancer, 42 who eventually developed esophageal cancer, and 772 controls who were matched for age, date of sample collection, and neighborhood of residence.
"After excluding subjects with less than 4 years of follow-up, the presence of EGC in the urine was related to an about 50% reduction in the risk of developing gastric and esophageal cancer," said Can-Lan Sun, MD, a researcher in the Department of Preventive Medicine, USC/Norris Comprehensive Cancer Center, Los Angeles. No such association was noted for EC.
Dr. Sun noted that EGC is a more specific marker for green tea, while EC is found in other commonly ingested foods and beverages such as apples, wine, and chocolate.