Tehran University of Medical Sciences Journal of Food Safety and Hygiene 2476-3241 6 4 2021 10 05 168 182 Azita Faraki University of Tehran Fatemeh Rahmani Department of Food Science and Technology, Gorgan University of Agricultural and Natural Resources, Gorgan,Iran 2021 04 27 2021 07 07 Probiotics and Lactic Acid Bacteria play important roles such as the production of antimicrobial compounds and other metabolites. So they have positive effects on human health. When reactive oxygen species generated in excess or cellular defenses are deficient, biomolecules can be damaged by the oxidative stress process. Various studies have shown that the best way to deal with the damages of oxidative reactions to protect the human body is to prevent them, which is possible by using compounds called antioxidants. Due to the damages of synthetic antioxidants, the usage of them has been discussed. Nowadays natural antioxidants from bio-resources have received a great deal of attention. Among probiotics beneficial effects, the protection against oxidative stress has been reported by many researchers. Based on the hypothesis of some scientists, probiotic bacteria exert their protective effects against oxidative stress by restoring gut microbiota. This type of microorganisms indicated their antioxidant activity by producing and increasing antioxidant enzymes, production of secondary metabolites, small hydrolyzed peptides in food, resistance to the presence of hydrogen peroxide, and production of intracellular and extracellular compounds such as Exopolysaccharides. Also, they have shown their positive effect on in vivo models. In conclusion, the results of studies indicated that lactic acid bacteria and probiotics are a major source of natural antioxidants, therefore, they have important research value and market development potential. Also, it should be noted that the mechanism of antioxidant activity of this group of microorganisms has not been fully investigated, this requires further research. https://jfsh.tums.ac.ir/index.php/jfsh/article/view/302 https://jfsh.tums.ac.ir/index.php/jfsh/article/download/302/153