SummaryBackgroundTo examine the effect of probiotics as adjunctive therapy for the treatment of rheumatoid arthritis (RA). A sample size of 30 subjects was calculated to determine a moderate effect.Material/MethodsA three month double-blind, placebo-controlled study was performed using probiotic Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 capsules administered orally. Inclusion criteria required at least 4 swollen and 4 tender joints and stable medications with no steroids for at least 1 month prior to and during the study. Twenty-nine patients with RA were randomized to treatment. ACR20 responses, serum cytokine levels and safety parameters were assessed.ResultsFifteen patients were randomized to the probiotic group, and 14 to placebo. Three subjects in the probiotic (20%) and one in the placebo group (7%) achieved an ACR20 response (p= 0.33). There was no statistically significant difference between individual components of the ACR20 criteria. Changes in cytokines favored placebo over probiotic. There was a significant improvement in the Health Assessment Questionnaire (HAQ) score in the probiotic group from visit 1 to visit 3 (p=0.02) but no between-group differences.ConclusionsDue to inclusion criteria, patients selected for the study had stable RA with chronic synovitis, and thus it may have been difficult for an adjunctive therapy to demonstrate improvement within 3 months. Although probiotics did not clinically improve RA as measured by the ACR20, it is interesting that there was functional improvement seen within the probiotic group compared to placebo.