Association Between Green Tea and Colorectal Cancer Risk: A Meta-analysis of 13 Case-control Studies

Objective: Experimental studies have suggested green tea to be a chemopreventive agent for colorectalcancer, and many studies have examined possible associations. However, the conclusions were inconsistent oreven contradictory, so we performed a meta-analysis based on published case-control studies to explore if greentea is indeed a protective factor.
Methods: PubMed was searched up to May 10th, 2012 for relevant studies, andreferences of included studies were manually searched. Finally 13 eligible studies, involving 12,636 cases and38,419 controls were identified. After data extraction, a meta-analysis was performed using CMA v2 software.
Results: The results indicated there may be a weak but not statistically significant reduced risk of colorectalcancer with high dose of green tea intake (OR=0.95, 95% CI:0.81-1.11, p=0.490.69–0.98). This protective effectwas also found in all subgroups, except in American and European populations. Sensitivity analysis indicatedthe result to be robust. Publication bias was not detected by either funnel plot or Egger tests.
Conclusion: Theresults of this meta-analysis indicate a weak lower tendency for colorectal cancer development with green teaconsumption, but available epidemiologic data are insufficient to conclude that green tea may protect againstcolorectal cancer in humans.