Causal Effect of Fatty Fish Consumption on Influenza: Evidence From Two-Sample Mendelian Randomization.

Background: Influenza continues to pose a significant public health threat, with substantial morbidity and mortality worldwide. While vaccines and antiviral treatments exist, the role of dietary factors, particularly fatty fish consumption, in modulating influenza susceptibility remains underexplored. Fatty fish, rich in omega-3 polyunsaturated fatty acids (PUFAs), is believed to influence immune responses, but its specific impact on influenza risk is not fully understood. This study aims to investigate the causal relationship between fatty fish consumption and influenza susceptibility using a two-sample Mendelian randomization (MR) approach. Methods: Genetic instruments for fatty fish consumption were derived from publicly available genome-wide association studies (GWAS). Summary-level data on influenza susceptibility were sourced from the largest GWAS available. A two-sample MR analysis was conducted using inverse-variance weighted (IVW) and MR-Egger methods to assess the causal effect of fatty fish consumption on influenza risk. Results: The analysis revealed a potential protective effect of higher fatty fish consumption on influenza susceptibility. Genetically predicted higher intake of fatty fish was associated with a reduced risk of influenza, suggesting that omega-3 PUFAs may help lower susceptibility to the virus. Sensitivity analyses confirmed the absence of horizontal pleiotropy, supporting the robustness of the results. Conclusion: This study provides evidence for a potential causal relationship between increased fatty fish consumption and a decreased risk of influenza. These findings have implications for dietary recommendations and public health strategies aimed at reducing influenza burden. However, this study has some limitations, such as the potential influence of gene-environment interactions and the predominantly European-based study population, which may limit generalizability. Future research should aim to replicate these findings in diverse populations and further explore the biological mechanisms linking fatty fish intake with influenza susceptibility.