The objective of this randomized double-blind placebo controlled trial is to assess the effect of probiotic yogurt and regular yogurt consumption on the components, inflammatory and oxidative markers and vascular endothelial function in patients with metabolic syndrome. Subjects will be recruited to the study, according to inclusion criteria: ages between 20 to 65 years; diagnosis of the metabolic syndrome based on definition of the Iranian National Committee of Obesity, and exclusion criteria: suffering from cardiovascular disease, renal failure, diabetes mellitus and gastrointestinal diseases; receiving supplements of probiotic during the two months before the study; pregnancy; lactation; menopause. Subjects including 44 individuals from both sexes will be randomly divided into two intervention and control groups, using a blocked randomization procedure of size of 4. Subjects in intervention and control group will receive 300 g daily of probiotic or regular yogurt respectively for 8 weeks. The assignment of groups will cover from the investigators and the subjects. Probiotic and regular yogurt containers will be identical looking and with three-digit code will be separable. Fasting blood samples, blood pressure and anthropometric measurements, appetite questionnaire, physical activity questionnaire, 3 dietary records for each person will be performed at the beginning and end of the study. The levels of markers of inflammatory and oxidative and vascular endothelial function, blood sugar, lipid profile and insulin in the fasting blood samples will be assessed.