Carcinogenesis Advance Access published online on August 27, 2007
Carcinogenesis, doi:10.1093/carcin/bgm171
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Green tea and black tea consumption in relation to colorectal cancer risk: the Singapore Chinese Health Study
1 City of Hope National Medical Center and Beckman Research Institute, Duarte, CA 91010
2 The Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA
3 Department of Community, Occupational and Family Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597
Address requests for reprints to: Can-Lan Sun, MD, Ph.D, Division of Population Sciences, City of Hope National Medical Center and Beckman Research Institute, 1500 E, Duarte Road, Duarte CA 91010 Email: casun{at}coh.org Phone: 626-256-4673 ext 64124 Fax: 626-930-5387
The relationships between green tea and black tea consumption and colorectal cancer risk were examined within the Singapore Chinese Health Study, a prospective cohort study of diet and cancer involving over 60,000 men and women. Intake of green tea and black tea was assessed through in-person interviews. Incident cancer cases and deaths among cohort members were identified through record linkage of the cohort database with respective databases from the nationwide Singapore Cancer Registry and the Singapore Registry of Births and Deaths. The proportional hazard regression method was used to examine the associations between intake of green and black tea separately and colorectal cancer risk with adjustment for potential confounders. After an average of 8.9 years of follow-up, 845 colorectal cancer cases were identified. Subjects who drank green tea exhibited a statistically non-significant increase in risk (RR = 1.12, 95% confidence interval (CI) = 0.97-1.29) relative to nondrinkers of green tea. This risk increase was mainly confined to men (RR = 1.31, 95% CI = 1.08-1.58); the comparable RR in women was 0.89 (95% CI = 0.71-1.12). In men, the green tea-colorectal cancer association was noted mainly in those with advanced disease (Duke C or D) (RR = 1.53, 95% CI = 1.19-1.97), and the association was dose-dependent (p for trend = 0.0002). This latter association was especially strong within the colon sub-site (RR = 1.75, 95% CI = 1.24-2.46; p for trend<0.0001). Irrespective of gender, intake of black tea was not associated with risk of colorectal cancer (RR = 0.92, 95% CI = 0.79-1.07) in this Asian population.
Key Words: black tea • green tea • colorectal cancer • cohort study
Received March 16, 2007; revised July 9, 2007; accepted July 19, 2007.