The causality between dietary intake and allergic diseases: A two-sample Mendelian randomization analysis

Allergic diseases are common chronic inflammatory conditions, which can affect multiple organs in severe cases, resulting in complex and varied clinical manifestations. Therefore, their management requires a more comprehensive and long-term strategy. A well-balanced diet is crucial in this context, as it regulates the immune system and improves atopic constitution, making it a key measure in preventing and controlling allergic diseases. Unlike observational studies prone to confounding and reverse causality, Mendelian randomization uses genetic variants as instrumental variables for stronger causal inference. This study employed the two-sample Mendelian randomization to investigate the potential causal relationships between 22 dietary factors and allergic diseases. The primary methods used were the weighted median method, MR-Egger regression, and inverse-variance weighted. To ensure the robustness and accuracy of the results, a series of sensitivity analyses, heterogeneity tests, and pleiotropy assessments were conducted. The study identified 7 dietary factors associated with allergic asthma, atopic dermatitis, and allergic rhinitis. The oily fish (OR: 0.666; 95% CI: 0.468-0.949; P = .024), dried fruit (OR: 0.463; 95% CI: 0.307-0.697; P = .00023), and cereal intake (OR: 0.595; 95% CI: 0.355-0.998; P = .049) was found to have a protective effect against asthma. The fresh fruit (OR: 0.592; 95% CI: 0.384-0.913; P = .018), tea (OR: 0.774; 95% CI: 0.603-0.995; P = .046), cereal (OR: 0.635; 95% CI: 0.430-0.939; P = .023), and processed meat intake (OR: 0.481; 95% CI: 0.294-0.787; P = .0036) were protective factors against atopic dermatitis. No significant causal relationships were observed between other dietary factors and these 3 diseases. These findings underscore the critical role of a balanced diet in the prevention and management of allergic diseases and highlight the potential of nutritional interventions in the future control and treatment of these conditions.