Subjects demonstrating the presence of tea polyphenols in their single-void urine specimens exhibit a lower risk for both cancers.
The new data, presented at the 93rd Annual Meeting of the American Association for Cancer Research (AACR), confirm reports from earlier retrospective research.
Tea polyphenols are antioxidants that have been shown to have chemoprotective benefits for cancers at these and other sites.
"We found approximately a 50% reduction in relative risk, which is confined to subjects with low serum levels of carotene, which is also an antioxidant," said Can-Lan Sun, a researcher in the Department of Preventive Medicine at USC/Norris Comprehensive Cancer Center in Los Angeles.
"It appears that tea polyphenols may play an important protective role in people who have low levels of other antioxidants."
Investigators at the USC/Norris Comprehensive Cancer Center collaborated with the Shanghai Cancer Institute on a prospective cohort study involving 18,244 middle aged or older men in Shanghai, China.
| Tea polyphenols may protect people who have low levels of other antioxidants.
Chinese men have a far higher risk for gastric and esophageal cancers than the United States population, but prognoses of these cancers are universally poor.
In this study, levels of two tea polyphenol markers were measured in urine samples taken from 190 men with gastric cancer and 42 men with esophageal cancer before their malignancies were diagnosed. The markers were epigallocatechin (EGC) and epicatechin (EC).
These data were compared with urinary EGC and EC levels for 772 control subjects from the same cohort, matched for age and other relevant factors to the cancer cases.
The investigators found a statistically significant association between presence of EGC in baseline urine and reduced risk of gastric and esophageal cancer among cohort subjects.
No such association was observed for EC.