Association between green tea/coffee consumption and biliary tract cancer: A population‐based cohort study in Japan

Green tea and coffee consumption may decrease the risk of some types of cancers. However, their effects on biliary tract cancer (BTC) have been poorly understood. In this population-based prospective cohort study in Japan, we investigated the association of green tea (total green tea, Sencha, and Bancha/Genmaicha) and coffee consumption with the risk for BTC and its subtypes, gallbladder cancer, and extrahepatic bile duct cancer. The hazard ratios and 95% confidence intervals were calculated using the Cox proportional hazard model. A total of 89 555 people aged 45-74 years were enrolled between 1995 and 1999 and followed up for 1 138 623 person-years until 2010, during which 284 cases of BTC were identified. Consumption of >720 mL/day green tea was significantly associated with decreased risk compared with consumption of ≤120 mL/day (hazard ratio = 0.67 [95% confidence interval, 0.46-0.97]), and a non-significant trend of decreased risk associated with increased consumption was observed (P-trend = 0.095). In the analysis according to the location of the primary tumor, consuming >120 mL green tea tended to be associated with decreased risk of gallbladder cancer and extrahepatic bile duct cancer. When Sencha and Bancha/Genmaicha were analyzed separately, we observed a non-significant trend of decreased risk of BTC associated with Sencha but no association with Bancha/Genmaicha. For coffee, there was no clear association with biliary tract, gallbladder, or extrahepatic bile duct cancer. Our findings suggest that high green tea consumption may lower the risk of BTC, and the effect may be attributable to Sencha consumption.