Tea consumption reduces the risk of oral cancer: a systematic review and meta-analysis

Oral cancer is one of the ten most common cancers in the world. The objective of this meta-analysis was to determine the association between tea consumption and risk of oral cancer. A comprehensive literature search was performed in PubMed, Embase and reference lists. A meta-analysis was performed by STATA software. Fifteen studies involving 5,491 oral cancer cases examining the association between tea consumption and risk of oral cancer were included. Among all the studies, 12 studies were case-control, and 3 were cohort studies. The relative risks (RRs) were pooled using a random-effects model. Relative risks with 95% confidence intervals (CIs) were used in the analyses. The pooled RR of included studies between tea drinking and risk of oral cancer was 0.85 (95% CI: 0.75-0.93). After stratifying by the study designs, a significant inverse association between tea drinking and oral cancer risk was observed in both cohort studies (n = 3; RR = 0.81; 95% CI: 0.66-1.0) and the case-control studies (n = 12; RR = 0.858; 95% CI: 0.777-0.948). A significant evidence of dose-response relationship was detected between tea consumption and oral cancer risk (P < 0.001). Findings from this meta-analysis suggest that tea consumption may reduce the risk of oral cancer. Because of the limited number of studies, further high-quality cohort or case-control studies are needed studies are needed to explore the protective effect of tea on oral cancer.