The polyphenols in tea can help protect drinkers against cancer of the stomach or the oesophagus, according to a recent study of tea drinkers in China.
Researchers from the Keck School of Medicine, University of Southern California (USC), Rutgers University and the Shanghai Cancer Institute studied male tea drinkers in Shanghai and discovered that they were around half as likely to develop cancer of the stomach or oesophagus as counterparts who drank little or no tea.
The results of the study, which is ongoing, were presented at the recent meeting of the American Association for Cancer Research.
In a study beginning in 1986, researchers followed 18,244 men aged 45 to 64 in the eastern Chinese coastal city and found 190 cases of gastric cancer and 42 cases of oesophageal cancer. The researchers compared the cancer patients to 772 similar men without cancer.
The team measured the polyphenols levels in each participant, as well as checking for levels of several chemicals produced when polyphenols breakdown in the body. Polyphenols included epigallocatechin (EGC) and epicatechin (EC).
They discovered that the presence of EGC in urine was associated with a lower risk of gastric and oesophageal cancer, after adjusting for smoking, alcohol drinking, carotenes (natural chemicals found in carrots, spinach and other vegetables and fruit) and H. pylori (a type of bacteria linked to peptic ulcers).
People who had lower-than-average levels of carotenes in their blood were most likely to benefit from the cancer-fighting properties of the tea polyphenols, the researchers suggested. Carotenes are also thought to help fight cancer and other diseases.
"This study provides direct evidence that tea polyphenols may act as chemo-preventive agents against gastric and oesophageal cancer development," said Mimi C. Yu, professor of preventive medicine at the Keck School of Medicine and member of the research team.
All varieties of tea come from the leaves of a single plant, Camellia sinensis. Its antioxidant properties - the ability to destroy dangerous free radicals, rogue molecules which themselves can destroy cells and genetic materials - have been studied for many years, and the popular beverage has been touted as a treatment for any number of diseases.
Green tea has the most powerful antioxidant properties, followed by oolong and black teas. In research studies, polyphenols have been shown to halt tumour cell growth as well as to protect healthy cells from damage. Just this week, green tea was touted as a possible treatment for muscular dystrophy.