Green tea consumption and gastric cancer in Japanese: a pooled analysis of six cohort studies
- M Inoue1,
- S Sasazuki1,
- K Wakai2,
- T Suzuki3,
- K Matsuo3,
- T Shimazu1,4,
- I Tsuji4,
- K Tanaka5,
- T Mizoue6,
- C Nagata7,
- A Tamakoshi8,
- N Sawada1,
- S Tsugane1,
- for the Research Group for the Development and Evaluation of Cancer Prevention Strategies in Japan
- 1Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo, Japan
- 2Department of Preventive Medicine/Biostatistics and Medical Decision Making, Nagoya University Graduate School of Medicine, Nagoya, Japan
- 3Division of Epidemiology and Prevention, Aichi Cancer Center Research Institute, Nagoya, Japan
- 4Division of Epidemiology, Department of Public Health and Forensic Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
- 5Department of Preventive Medicine, Faculty of Medicine, Saga University, Saga, Japan
- 6Department of Epidemiology and International Health, Research Institute, International Medical Center of Japan, Tokyo, Japan
- 7Department of Epidemiology and Preventive Medicine, Gifu University Graduate School of Medicine, Gifu, Japan
- 8Department of Public Health, Aichi Medical University School of Medicine, Aichi, Japan
- Correspondence to Dr M Inoue, Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045 Japan; mnminoue{at}ncc.go.jp
- Revised 8 April 2009
- Accepted 16 May 2009
- Published Online First 7 June 2009
Abstract
Background: Previous experimental studies have suggested many possible anti-cancer mechanisms for green tea, but epidemiological evidence for the effect of green tea consumption on gastric cancer risk is conflicting.
Objective: To examine the association between green tea consumption and gastric cancer.
Methods: We analysed original data from six cohort studies that measured green tea consumption using validated questionnaires at baseline. Hazard ratios (HRs) in the individual studies were calculated, with adjustment for a common set of variables, and combined using a random-effects model.
Results: During 2 285 968 person-years of follow-up for a total of 219 080 subjects, 3577 cases of gastric cancer were identified. Compared with those drinking <1 cup/day, no significant risk reduction for gastric cancer was observed with increased green tea consumption in men, even in stratified analyses by smoking status and subsite. In women, however, a significantly decreased risk was observed for those with consumption of ⩾5 cups/day (multivariate-adjusted pooled HR = 0.79, 95% confidence interval (CI) = 0.65 to 0.96). This decrease was also significant for the distal subsite (HR = 0.70, 95% CI = 0.50 to 0.96). In contrast, a lack of association for proximal gastric cancer was consistently seen in both men and women.
Conclusions: Green tea may decrease the risk of distal gastric cancer in women.
Footnotes
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Funding This study was supported by a Grant for the Third Term Comprehensive Control Research for Cancer from the Ministry of Health, Labour and Welfare of Japan. Financial disclosure: none.
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Competing interests None.
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Provenance and Peer review Not commissioned; externally peer reviewed.
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Ethics approval Approval for this study was given by the National Cancer Center, Tokyo, on 17 September 2008; by the Tohoku University Graduate School of Medicine on 24 July 2000 and 23 October 2000; by the Aichi Medical University on 7 July 2008; and by the Aichi Cancer Center, Nagoya, on 31 March 1986.
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Members of the Research Group for the Development and Evaluation of Cancer Prevention Strategies in Japan
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S Tsugane (principal investigator), M Inoue, S Sasazuki, M Iwasaki, T Otani (until 2006), N Sawada (since 2007), T Shimazu (since 2007) (National Cancer Center, Tokyo); I Tsuji (since 2004), Y Tsubono (in 2003) (Tohoku University, Sendai); Y Nishino (until 2006) (Miyagi Cancer Research Institute, Natori, Miyagi); K Wakai (Nagoya University, Nagoya); K Matsuo (since 2006) (Aichi Cancer Center, Nagoya); C Nagata (Gifu University, Gifu); T Mizoue (International Medical Center of Japan, Tokyo); K Tanaka (Saga University, Saga).
