Plant-Based Diets and Rheumatoid Arthritis: What the Evidence Shows

Rheumatoid arthritis is characterised by chronic synovial inflammation driven by auto-reactive T cells. Diet influences RA through its effects on systemic inflammation, gut microbiome composition, gut barrier integrity, and specific immune pathways. A 2001 Norwegian RCT found that adults with RA placed on a vegan diet for 3.5 months had significant reductions in disease activity, tender and swollen joint counts, ESR, CRP, and rheumatoid factor, with effects persisting in a subset who remained on a lacto-vegetarian diet for a further year.

Dietary Mechanisms Relevant to Rheumatoid Arthritis

• Gut microbiome and RA: adults with RA have significantly reduced microbiome diversity and higher Prevotella copri populations compared to healthy controls; plant fibre diversity supports microbiome compositions associated with lower RA disease activity
• Gut permeability: increased gut permeability allows bacterial products to enter the bloodstream and activate immune responses; plant fibre from legumes and vegetables supports tight junction integrity
• Omega-3 fatty acids: EPA and DHA from oily fish and algae-derived omega-3 reduce inflammatory eicosanoid production; multiple RCTs show reduced NSAID requirements with fish oil supplementation in RA
• Arachidonic acid reduction: arachidonic acid from red meat is the substrate for pro-inflammatory prostaglandins and leukotrienes; reducing animal food intake reduces arachidonic acid substrate availability