Association of Green Tea Consumption and the Risk of Liver Cancer Incidence among Japanese Adults

BACKGROUND: The association between green tea consumption and the risk of liver cancer has been reported inconsistently. This study aimed to investigate this association in a large, prospective cohort study of Japanese adults. Methods: The Japan Collaborative Cohort (JACC) Study included 41,999 participants (18,205 men and 23794 women) aged 40-79 years, free from liver cancer at baseline between 1988 and 1990. Validated self-administered questionnaires were used to assess individual socio-demographics, medical history, and lifestyles. Participants were then followed for liver cancer incidence until the end of 2009. Cox proportional hazard models were utilized to calculate hazard ratios (HRs) with 95% confidence intervals (95% CIs) of liver cancer based on the frequency of green tea consumption of <1 cup (reference), 2-4, 5-6, and ≥7 cups/day, after adjusting for potential confounding factors, including age, sex, study area, education, histories of diabetes, liver diseases, and gallbladder disease, body mass index, drinking status, smoking status, coffee consumption, sports participation, and walking. Major confounders, including coffee consumption, drinking status, and a history of liver disease, were further stratified in the analysis. Population-attributable fractions (PAFs) of liver cancer was also calculated based on green tea consumption. RESULTS: Green tea consumption was associated with a trend of lower risk of liver cancer with the multivariable HR (95% CI) of 0.87 (0.61-1.23) for 2-4 cups/day, 0.87 (0.61-1.25) for 5-6 cups/day, and 0.61 (0.40-0.95) for ≥7 cups/day, compared to <1 cup/day (p for trend= 0.029). The inverse association was statistically significant for men, people without a history of liver diseases other than cancer, and current drinkers. The multivariable PAF (95%CI) for ≥7 cups/day was 7.1% (0.9-11.4). CONCLUSION: Green tea consumption was associated with a lower risk of liver cancer in Japanese adults in a dose-response manner, ranging from <1 cup/day to ≥7 cups/day.