Plants for health Investigating the broader impacts of the Plants for Joints lifestyle intervention

This thesis builds upon the Plants for Joints (PFJ) randomized controlled trials (RCTs), which demonstrated significant improvements in disease activity in rheumatoid arthritis (RA), as well as pain, stiffness, and physical function in osteoarthritis (OA). It extends these findings by investigating secondary effects, underlying mechanisms, perceived usefulness, cost-effectiveness, and long-term outcomes of the PFJ lifestyle intervention.
A systematic review showed that high-fiber, plant-based diets are consistently more effective at improving clinical and microbiome outcomes in chronic inflammatory diseases, compared to other dietary patterns. Secondary analyses of the PFJ RCTs showed significant reductions in body fat and liver fat content, improvements in gut barrier integrity, favorable shifts in microbiome composition and metabolites, and positive effects on stress-related parameters in RA. Further research indicated no evidence of mucosal anti-modified protein antibody production in the gut.
A process evaluation highlighted high participant satisfaction, empowerment, and the importance of self-monitoring, social support, and guidance. Economic analyses demonstrated that the PFJ intervention was on average less costly and more effective compared to only usual care. Long-term follow-up over two years showed sustained improvements in disease activity, pain, stiffness, physical function, several metabolic risk factors, and reduced medication use, with continued adherence to intervention recommendations.
Together, these findings show PFJ is a feasible, acceptable, and sustainable lifestyle intervention with broad health benefits. Beyond symptom relief, PFJ positively influences body composition, metabolic health, the gut microbiome, stress regulation, and quality of life, underscoring its potential as an adjunct treatment for RA, OA, and possibly other chronic diseases.