Saliva plays a central role in the complex physiological and biological processes that take place in the upper parts of the gastrointestinal tract in relation to ingestion and processing of the food. Human saliva has a number of physical, physicochemical and chemical agents that protect oral tissues against by various microorganisms and their metabolic products. Antimicrobial peptides with other innate defense molecules are fighting infection and control residents microbial populations throughout the oral cavity.