Psoriasis is an inflammatory skin disease, presenting as elevated and red cutaneous lesions, adversely impacting people’s quality of life. Given the link between diet and inflammation and the unclear role of diet quality in the onset of psoriasis (1), this study used the large-scale UK Biobank to explore the association between dietary patterns and psoriasis incidence.

The study included 121,584 UK Biobank participants who were initially free of psoriasis and followed for an average of 14 years. Participants in this analysis were free from chronic inflammatory infectious disease (HIV and chronic viral hepatitis) and had completed at least two 24-hour dietary recalls. Nine diet quality indices were computed, including the Low Carbohydrate Diet Score (LCDS), Alternative Mediterranean Diet (aMed) Score, Eatwell Score, Alternative Binary Eatwell Score, Alternative Graded Eatwell Score, Healthy Diet Index (HDI), Alternative Healthy Eating Index (aHEI), Dietary Approaches to Stop Hypertension Score (DASH), Dietary Inflammatory Index (DII), and Plant-Based Diet Index (PDI) with the addition of alcohol-excluded scores (aMed-nonalc, aHEI-nonalc) to account for the known link between alcohol and psoriasis risk (2). The primary outcome of this study was the incidence of psoriasis, determined through self-reported diagnosis, primary care (GP), and hospital admission data.

Of the 121,584 participants, 1,087 developed psoriasis, yielding an incidence rate of 0.89%. Participants who developed psoriasis reported significantly lower DASH (24.85 ± 4.53 vs. 25.19 ± 4.55, P = 0.017) and PDI (54.28 ± 5.51 vs. 54.82 ± 5.52, P = 0.001) scores, as well as less negative (pro-inflammatory) DII scores (-0.47 ± 1.78 vs. -0.58 ± 1.76, P = 0.039), compared to participants who did not develop psoriasis. Each increment in aMed (HR: 0.95, 95% CI: 0.92–0.99), aMed-nonalc (HR: 0.95, 95% CI: 0.92–0.98), DASH (HR: 0.98, 95% CI: 0.97–1.00), and PDI (HR: 0.98, 95% CI: 0.97–0.99) score was associated with lower psoriasis risk, while a higher DII (HR: 1.04, 95% CI: 1.00–1.07) was linked to an increased risk of psoriasis onset. After adjusting for age, sex, Townsend deprivation index, socioeconomic status, physical activity, smoking status, alcohol consumption, and comorbidities, each 1-point increment in the PDI score was associated with a modest 2% reduction in psoriasis risk. This association persisted after further adjustment for BMI. However, no significant associations were found for other dietary scores, both before and after BMI adjustment.

In this large cohort, greater adherence to the PDI was associated with a modestly lower risk of psoriasis, suggesting the potential benefits of plant-based diets in reducing psoriasis risk. Future research should prioritize randomized controlled trials to confirm this relationship.