Ultra-Processed Food Consumption and the Risk of Psoriasis: A Large Prospective Cohort Study

Background: The sales of ultra-processed food (UPF) are rapidly increasing worldwide, and there have been reports linking UPF consumption to several chronic diseases. However, there is limited prospective evidence exploring the impact of UPF on inflammatory skin diseases. Objectives: This study investigates the association between UPF intake and the incidence of psoriasis using data from the UK Biobank. Methods: UPFs were assessed based on the NOVA classification in this large prospective study. Cox proportional hazards regression was employed to estimate the association between UPF intake and the incident risk of psoriasis. Inflammation score (INFLA-score) and body mass index (BMI) were chosen as mediators to examine the mediation effect. Substitution analysis was performed to estimate the psoriasis risk when replacing the absolute amount of UPF with an equivalent weight of unprocessed or minimally processed food. Results: This study enrolled 121,019 participants aged 40-69 years from the UK Biobank. Over a 12-year (median) follow-up period, 1043 participants developed psoriasis. In the fully adjusted model, hazard ratios (95% confidence interval) for psoriasis across increasing quartiles of UPF consumption were 1.00 (reference), 1.07 (0.89, 1.28), 1.19 (1.00, 1.42), and 1.23 (1.03, 1.47), respectively (p for trend = 0.016). Factors such as age, sex, BMI, smoking status, drinking status, physical activity level, and Townsend Deprivation Index (TDI) did not significantly modify this association (p interaction > 0.05). The INFLA-score and BMI explained 6.5% (p = 0.012) and 30.5% (p < 0.001) of the association between UPF consumption and psoriasis risk, respectively. Replacing 20% of UPF weight in total diet with an equivalent proportion of unprocessed or minimally processed foods was associated with an 18% reduction in psoriasis risk (HR: 0.82; 95% CI: 0.72-0.94; p = 0.004). Conclusions: Our findings indicate that increased UPF consumption is associated with a higher risk of psoriasis. This provides valuable dietary guidance for preventing psoriasis and its related comorbidities.