Fermented milk contains special therapeutic or prophylactic properties against cancer and lactose intolerance. Fermentation also improves food safety through the inhibition of pathogens and the removal of toxic compounds in foods. These significant changes cause desirable biochemical effects that lead to the development of new aromas, flavors, organoleptic characteristics and textures, thus increasing the sensorial quality, palatability and acceptability of the product. Researchers over the last decade have shown that biologically active peptides are released from caseins, and whey proteins contain 3 to 20 amino acids per molecule during fermentation. These bioactive compounds contain very important biological functionalities, such as antimicrobial, antihypertensive, antioxidant, anticytotoxic, immunomodulatory, opioid, and mineral transporting activities. Most milk bioactivities are latent, being absent or incomplete in the original native proteins, but complete activities manifest during proteolytic digestion to release and activate bioactive compounds encrypted by the original protein. Bioactive compounds are specific protein fragments found in milk that regulate gastrointestinal development, infant development, immunological function, and microbial activity