Study aim: he aim of this study is to determine the effects of probiotic supplementation on disease severity and metabolic profiles in patients with multiple sclerosis. Design: Parallel double-blind (both patients and researchers) randomized controlled clinical trial. Random assignment will be done by the use of computer-generated random numbers. Settings and conduct: 60 patients with multiple sclerosis of eligible and referred to Beheshti Clinic affiliated to Kashan University of Medical Sciences, Kashan, Iran in the study will be selected. Participants/Inclusion and exclusion criteria: Peoples will be entered in the study if they will be at ages between 18 and 55 with clinically definite RRMS will be diagnosed according to McDonald criteria and an expanded disability status scale (EDSS) score ≤4.5. The participants will be excluded from the study under following conditions: women who were pregnant or lactating during the past six months, patients bearing nephrolithiasis for the past 5 years, menopaused women with irregular menstruation and unwillingness to utilize appropriate contraceptive tools. Intervention groups: Patients will be assigned to receive either probiotic supplements (intervention group: n=30) and placebo (control group: n=30). Main outcome variables: Fasting blood samples will be taken at baseline and after 12-wk intervention. Disease severity and metabolic profiles will be meseaured at study baseline and end-of-trial.