Objective: To examine and quantify the potential dose-response relationship between green tea intake and the risk of gastric cancer.
Design: We searched PubMed, EMBASE, Web of Science, CBM, CNKI and VIP up to December 2015 without language restrictions.
Setting: A systematic review and dose-response meta-analysis of observational studies.
Subjects: Five cohort studies and eight case-control studies.
Results: Compared with the lowest level of green tea intake, the pooled relative risk (95 % CI) of gastric cancer was 1·05 (0·90, 1·21, I 2=20·3 %) for the cohort studies and the pooled OR (95 % CI) was 0·84 (0·74, 0·95, I 2=48·3 %) for the case-control studies. The pooled relative risk of gastric cancer was 0·79 (0·63, 0·97, I 2=63·8 %) for intake of 6 cups green tea/d, 0·59 (0·42, 0·82, I 2=1·0 %) for 25 years of green tea intake and 7·60 (1·67, 34·60, I 2=86·5 %) for drinking very hot green tea.
Conclusions: Drinking green tea has a certain preventive effect on reducing the risk of gastric cancer, particularly for long-term and high-dose consumption. Drinking too high-temperature green tea may increase the risk of gastric cancer, but it is still unclear whether high-temperature green tea is a risk factor for gastric cancer. Further studies should be performed to obtain more detailed results, including other gastric cancer risk factors such as smoking and alcohol consumption and the dose of the effective components in green tea, to provide more reliable evidence-based medical references for the relationship between green tea and gastric cancer.
Keywords: Dose–response; Gastric cancer; Green tea; Meta-analysis.