Tea drinking and the risk of biliary tract cancers and biliary stones: a population-based case-control study in Shanghai, China.

Biliary tract cancers, encompassing tumors of the gallbladder, extrahepatic bile ducts and ampulla of Vater, are rare but highly fatal malignancies. Apart from gallstones, etiologic factors for biliary tract cancer are not clearly defined. Several epidemiologic studies have suggested that consumption of tea, especially green tea, is protective against a variety of cancers, including gastrointestinal malignancies. As part of a large population-based case-control study of biliary tract disease in Shanghai, China, we evaluated the effects of tea consumption on the risk of biliary tract cancers and biliary stones. The study included 627 incident cases with biliary tract cancer, 1,037 cases with biliary stones and 959 randomly selected controls. Study subjects were interviewed to ascertain data on demographic, medical and dietary factors, including tea consumption. Forty-one percent of the controls were ever tea drinkers, defined as those who consumed at least 1 cup of tea per day for at least 6 months. After adjustment for age, education and body mass index, among women, ever tea drinkers had significantly reduced risks of biliary stones (OR = 0.73, 95% CI = 0.54-0.98) and gallbladder cancer (OR = 0.56, 95% CI = 0.38-0.83). The inverse relationship between tea consumption and gallbladder cancer risk was independent of gallstone disease. Among men, tea drinkers were more likely to be cigarette smokers, and the risk estimates were generally below 1.0, but were not statistically significant. Further studies are needed to confirm these results in other populations and clarify the hormonal and other mechanisms that may be involved.