Associations between flavonoid intake, genetic risk of psoriasis, and psoriasis incidence: a prospective cohort study

Psoriasis is a chronic inflammatory skin disease with substantial impact on quality of life. This study aimed to investigate the relationship between flavonoid intake and the risk of developing psoriasis, and to assess whether genetic predisposition modifies this association. This prospective study included 121 299 UK Biobank participants free of psoriasis at baseline who completed at least two Oxford WebQ dietary recalls. Incident psoriasis was identified using self-reports, primary care data, and hospital records. Intake of total flavonoids and five subclasses (anthocyanins, flavanones, flavan-3-ols, flavonols, and flavones) was estimated. Multivariable Cox proportional hazards models were used to assess associations, adjusting for sociodemographic, lifestyle, dietary, and clinical factors. Polygenic risk scores (PRS) for psoriasis were used for stratified analyses and interaction testing. Over a mean follow-up of 11.4 years, 822 incident psoriasis cases were identified (0.68%). Moderate flavone intake (0.6-1.5 mg d^-1; Q2) was associated with a lower risk of psoriasis (HR 0.66; 95% CI 0.52-0.84), particularly among participants with high PRS, with evidence of a nonlinear association. Similar inverse associations were observed for flavone-rich foods. However, no significant interaction between flavone intake and PRS was detected. Given the low intake levels and the co-occurrence of flavones within nutrient-rich foods, this non-linear association should be interpreted cautiously and may reflect broader diet quality rather than flavone-specific effects.