To study the causal relationship between tea intake and the incidence of colorectal cancer using two-sample Mendelian randomization.

Using the colorectal cancer genome-wide association analysis data (GWAS ID: ieu-b-4965) and tea intake genome-wide association analysis data (GWAS ID: ukb-b-6066) in the IEU OPEN GWAS public database, we summarized and screened the two data sets for single nucleotide polymorphisms (SNPs) which were closely related to and independent of tea intake as instrumental variables (IVs). By using MR-Egger and inverse variance weighting in two-sample Mendelian randomization, Five methods (IVW), weighted median method (Weighted Median), simple model (Simple Mode) and weighted model (Weighted Mode) were used to determine the causal analysis between tea intake and the incidence of colorectal cancer. OR and 95% CI were used to examine the causal relationship between tea intake and the incidence of colorectal cancer. MR-PRESSO was used for outlier testing. IVW (Cochran Q test) and MR-Egger (Rücker Q test) were used for heterogeneity analysis. Egger-intercept was used for pleiotropy test, sensitivity analysis was performed by leave-one-out method, and funnel plot was used to analyze the presence of potential bias.

39 SNPs were finally included, and MR-PRESSO found no outlier SNPs, P=0.237>0.05; in terms of causality determination: IVW (OR=0.996, 95% CI:0.990-1.002, P=0.293), MR-Egger (OR=0.992, 95% CI:0.977-1.007, P=0.293), Weighted Median (OR=0.997, 95% CI: 0.987-1.007, P=0.479), Simple Mode (OR=0.996, 95% CI: 0.976-1.017, P=0.724), Weighted Mode (OR=0.996, 95% CI: 0.985-1.007, P=0.473). The above results showed that there was no causal relationship between tea intake and the incidence of colorectal cancer. In the heterogeneity test, P=0.181>0.05 in Cochran Q test and P=0.167>0.05 in Rucker Q test. There was no significant heterogeneity. The Egger-intercept test showed that P=0.489>0.05 and was not pleiotropic. The leave-one-out method was removed one by one, and no SNPs significantly affecting the results were found. The funnel plot was basically symmetrical, indicating that the main results were reliable.

There is no causal relationship between tea intake and the incidence of colorectal cancer.