Abstract
It is well known that the tea extracts, mainly polyphenols as chemo-preventive elements, could act as cancer progression blockers. Although the association between tea consumption and colorectal cancer risk has been widely investigated, the results still remain inconsistent. We conducted a dose-response meta-analysis to evaluate their relationships by enrolling qualified 29 literatures. The summary odds ratio (OR) of colorectal cancer for the highest vs. lowest tea consumption was 0.93 with 0.87–1.00 of 95% confidence intervals (CIs) among all studies with modest heterogeneity (P = 0.001, I2 = 43.4%). Stratified analysis revealed that tea, especially green tea, had a protective effect among female and rectal cancer patients. Particularly, the dose-response analysis showed that there was a significant inverse association between an increment of 1 cup/day of tea consumption and colorectal cancer risk in the subgroup of the green tea drinking (OR = 0.98, 95% CI = 0.96–1.01, Pnonlinear = 0.003) and female (OR = 0.68, 95% CI = 0.56-0.81, Pnonlinear < 0.001). Our findings indicate that tea consumption has an inverse impact on colorectal cancer risk, which may have significant public health implications in the prevention of colorectal cancer and further similar researches.
Highlights
Colorectal cancer (CRC) is one of the most common malignances occurred in the digestive system
18 of 54 articles were excluded for the following reasons: no available data on tea consumption (n = 1) or CRC risk (n = 4), no quantitative analysis on tea consumption (n = 12) and no odds ratios/relative risks (ORs/RRs) or 95% confidence internals (CIs) (n = 1)
A cohort study performed in the United States suggested that there seemed no inverse association between tea consumption and CRC [36]
Summary
Colorectal cancer (CRC) is one of the most common malignances occurred in the digestive system. As colorectal cancer is still a challenging global health problem, urgent primary prevention strategies are warranted. Many studies focused on the functions of tea in the development and progress of CRC, because tea is a kind of common worldwide beverage and known as a chemo-preventive actor for various diseases [4, 5]. Epidemiological studies have indicated that epigallocatechin-3-gallate (EGCG), the most luxuriant www.impactjournals.com/oncotarget and vigorous polyphenol in green tea, could modulate the signal transduction and metabolic pathways. It can cause cellular behavior changes, including apoptosis, proliferation and angiogenesis [3, 6]. Several studies even suggested that tea containing mutagenic and genotoxic compounds could raise the risk of CRC [7]
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