Effects of vegetarian and vegan diets on disease activity, pain, fatigue, and physical function in patients with rheumatoid arthritis: a systematic review and meta-analysis

BACKGROUND: This systematic review and meta-analysis aim to assess the effects of vegan and vegetarian diets on disease activity, pain, fatigue, and physical function in people with rheumatoid arthritis.

METHODS: We conducted searches on the MEDLINE, EMBASE, CINAHL, and Central electronic databases up to December 2024. Randomized controlled trials that investigated vegan or vegetarian dietary interventions (including lacto-ovo-vegetarian, vegan, or whole-food plant-based diets) in people with rheumatoid arthritis were included, and independent of outcomes measured.

RESULTS: Of 1408 screened hits, seven trials published between 1979 and 2023 were included. Pooled analyses revealed that compared to controls, participants following vegetarian or vegan diet achieved no significant improvement in disease activity, a small significant improvement in pain, and no significant improvement in physical function. Fatigue was only assessed in one of the included studies and thus not eligible for meta-analysis. The sensitivity and subgroup analyses did not change the outcome of the meta-analysis. The overall certainty of evidence (Grading of Recommendations, Assessment, Development, and Evaluations) for the effect of vegan and vegetarian diets in patients with rheumatoid arthritis was rated as low across all outcomes.

CONCLUSION: The meta-analysis suggests potential beneficial effects on pain. However, due to the methodological limitations and the small number of studies included, definitive conclusions cannot yet be drawn. Future research is needed to further explore the effects of vegetarian and vegan diets.

TRIAL REGISTRATION: The protocol was registered in PROSPERO CRD42023495226.