Exploring the Use of Diet and Support Needs of People Living with Psoriasis

Background Psoriasis is a chronic immune-mediated skin condition affecting approximately 60 million people globally. It is associated with substantial comorbidities, and while lifestyle factors may help manage psoriasis, research on the use and effectiveness of diet remains limited, particularly in the UK. With approximately 2% of adults living with psoriasis in the UK, this represents an important knowledge gap. This thesis aims to explore the role of diet in psoriasis management, to enhance our understanding of how to support people living with psoriasis (PLwP) in the UK. Methods A mixed-methods sequential design was used, and 4 studies were undertaken. Firstly, a scoping review was conducted to provide a comprehensive overview of the current evidence. To explore the dietary experiences of PLwP in the UK both qualitative and quantitative methods were utilised. Given the limited research thematic analysis of qualitative interviews was conducted to gain initial insights into the dietary modifications and experiences of PLwP in the UK. Based on these findings, a cross-sectional questionnaire was developed to quantitively explore the dietary modifications, skin responses, patient experiences, and information acquisition, among a larger population. The data from the first 3 studies informed the development of a dietary support guide for PLwP utilising a user-centered design (UCD) approach, incorporating think aloud methodology; its usability was evaluated using the System Usability Scale. Results The scoping review revealed that randomized control trials (RCTs) support low-calorie diets for those living with overweight or obesity and gluten-free diets for those with coeliac disease, to improve psoriasis. Further evidence is limited, and patient information rarely provides dietary support. Research on dietary use and experiences of PLwP has not been explored in the UK. Interviews with PLwP in the UK (n=9) revealed that most believed diet affected their psoriasis and tried restrictive diets, with limited success. Participants commonly sought dietary information online due to perceived lack of support from healthcare professionals (HCPs). The subsequent cross-sectional questionnaire (n=271) revealed that 47.2% of PLwP reported making a dietary modification to help their psoriasis. Common restrictions included high-sugar foods (64.1%) and dairy (63.3%). Participants with severe psoriasis (OR 2.268; p=0.027), aged 18-44 (OR 2.050; p=0.007), psoriatic arthritis (OR 2.754; p=0.003), or gluten sensitivity (OR 3.579; p=0.004) were more likely to have tried a dietary modification compared to those without these characteristics. Most (61.3%) changed their diet to also improve overall health, and (53.6%) wanted more dietary support. The dietary support guide was developed with an expert panel (n=7), and intended users (n=7). The final guide was evaluated as having good usability and was perceived to be useful and valuable by intended users (n=27). Conclusion Dietary modification is common among PLwP in the UK, primarily motivated by a desire to improve psoriasis and overall health. However, the majority of dietary modifications undertaken are unsubstantiated and restrictive. There is a need and desire for dietary support for PLwP. This thesis makes a notable contribution to patient-centred psoriasis care by directly addressing the identified dietary support gap, through the development of an evidence-based dietary support guide for PLwP. The involvement of PLwP and stakeholders in the development ensured it was usable and valuable to PLwP. Future research should assess the use and impact of the dietary support guide, and its value to HCPs. Additionally, larger, long-term studies to explore the impact of diet on psoriasis, and exploration of how nutritional support can be integrated into psoriasis care is needed.