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

Abstract

Objective: Experimental studies have suggested green tea to be a chemopreventive agent for colorectal cancer, and many studies have examined possible associations. However, the conclusions were inconsistent or even contradictory, so we performed a meta-analysis based on published case-control studies to explore if green tea is indeed a protective factor. Methods: PubMed was searched up to May 10 th , 2012 for relevant studies, and references of included studies were manually searched. Finally 13 eligible studies, involving 12,636 cases and 38,419 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 colorectal cancer with high dose of green tea intake (OR=0.95, 95% CI:0.81-1.11, p=0.490.69-0.98). This protective effect was also found in all subgroups, except in American and European populations. Sensitivity analysis indicated the result to be robust. Publication bias was not detected by either funnel plot or Egger tests. Conclusion: The results of this meta-analysis indicate a weak lower tendency for colorectal cancer development with green tea consumption, but available epidemiologic data are insufficient to conclude that green tea may protect against colorectal cancer in humans.

Flavonoid intake from vegetables and fruits is inversely associated with colorectal cancer risk: a case–control study in China

“…The National Cancer Institute-Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial found that greater tea intake was not associated with colorectal cancer risk (RR 0•77; 95 % CI 0•55, 1•09 for the highest quartile v. the lowest) (42) . Two meta-analyses summarised the results of case-control studies and prospective studies and found that data were insufficient to conclude that green tea may protect against colorectal cancer (43,44) .…”

Recent advances in clinical practice: colorectal cancer chemoprevention in the average-risk population

“…49 50 Two meta-analyses investigated he effect of green tea consumption on CRC risk, with the first reporting a significant effect, 51 but not the second. 48 In subsite analysis, the protective effect was found in rectal cancer only (OR=0.91; 95% CI 0.85 to 0.99). 50 In gender subgroup analysis, high consumption of tea and black tea (1 to 5 cups/day) were both reported to be protective against CRC in women (OR=0.86; 95% CI 0.78 to 0.94 50 and OR=0.82; 95% CI 0.70 to 0.95, 51 for any type of tea and black tea, respectively).…”

“…t. Heterogeneity was reported in three meta-analyses 26 50 51 but none in one. 48 u. Heterogeneity was noted in one meta-analysis 54 .…”

Green Tea and Its Extracts in Cancer Prevention and Treatment

“…In another meta analysis by Sun et al [119] a protective effect of green tea for colon cancer was calculated in three case control studies (OR 0.74, CI 0.60-0.93), whereas for other sites (rectal cancer) or other study types (cohort studies) no significant protective effect was seen. Wang et al [120] reanalyzed 13 case control studies with 12,636 cases. This analysis calculated an OR of 0.95 (CI 0.81-1.11) for studies from China whereas in subgroups a trend toward a protection against CRC was observed; in studies from Europe the OR was 1.00 or larger [120].…”

“…Wang et al [120] reanalyzed 13 case control studies with 12,636 cases. This analysis calculated an OR of 0.95 (CI 0.81-1.11) for studies from China whereas in subgroups a trend toward a protection against CRC was observed; in studies from Europe the OR was 1.00 or larger [120].…”