Stomach maintains a high acidic medium due to the secretion of HCl to
allow absorption of vitamin B12 which occurs in acidic conditions
allow absorption of some amount of water and alcohol
protect the GI tract from getting invaded by the microorganisms
allow breakdown of fats as lipolytic enzymes work in acidic conditions
Stomach protects the GI tract from getting invaded by the microorganisms due to the secretion of HCl which maintains acidic medium