Causal relationship of garlic or onion with gastric cancer based on a Mendelian randomization study

In observational studies, it has been known that garlic or onions have a negative causal relationship with gastric cancer (GC). In this study, we aim to explore the negative causal relationship between garlic or onion and GC through Mendelian randomization (MR) analysis. The instrumental variable selection for MR analysis is single nucleotide polymorphisms associated with garlic or onion, mainly using the inverse variance weighted method, combined with MR Egger, weighted media, simple mode, and weighted modes to evaluate their causal impact on GC. In addition, sensitivity analysis such as Cochran Q test, pleiotropy test, and leave-one-out method were used to evaluate the robustness of the impact of these single nucleotide polymorphisms on GC. The inverse variance weighted method showed a negative correlation between garlic and GC risk (odds ratio = 0.70; 95% confidence interval 0.49-0.99; P = .046), while there was no relationship between onion and GC, and the sensitivity analysis results showed robustness. The current study has revealed that garlic may be a factor in reducing the risk of GC, providing a strategy for preventing and treating GC.