CAT and rheumatoid arthritis: No significant difference was observed within or between probiotic and placebo group in serum malondialdehyde, total antioxidant capacity, and catalase activity. Erythrocyte superoxide dismutase activity decreased significantly in probiotic group and glutathione peroxidase activity decreased in both groups. Difference between two groups was insignificant for both groups at the end of the studyKey note: Probiotic supplementation does not have significant effect on oxidative status of RA patients