Assessment of the causal associations between dietary factors and psoriasis: A two-sample Mendelian randomization study

Objective: It has been reported that dietary factors may be closely associated with skin psoriasis. However, their causal associations with psoriasis remain elusive. This study aimed to clarify the relationships between genetic determinants for dietary habits and psoriasis through the application of Mendelian randomization (MR) approaches. Methods: Genome-wide association study (GWAS) data were leveraged to evaluate 34 common dietary habits in relation to psoriasis. The primary methodological framework utilized the multiplicative random-effects inverse variance-weighted (MRE-IVW) approach, supported by the MR-Egger and weighted median approaches, to ascertain the causal relevance. External GWAS summary statistics for psoriasis were used for replication analyses. For the dietary factors that were found to be associated with psoriasis in the discovery phase, secondary MR analyses were applied to clarify their causal roles in different subtypes of psoriasis. Results: The MRE-IVW analysis revealed that genetic predispositions for higher intakes of cereals (OR = 0.495, 95% CI : 0.266–0.919, P = 0.026) and dried fruits (OR = 0.399, 95% CI : 0.197–0.808, P = 0.011) had nominal correlations with reduced odds of psoriasis. These nominal inverse correlations were supported by the replication analyses. The secondary analyses revealed protective effects for the consumption of cereals and dried fruits on arthropathic psoriasis and psoriasis vulgaris, respectively. Conclusion: The present findings support increased intakes of cereals and dried fruits as potential protective factors against psoriasis.