Hydrochloric acid stimulates the production of hormones and destroys some of the harmful bacteria and other microorganisms in food particles. It aids in chemical digestion, and helps to break down certain nutrients. Too much hydrochloric acid, however, can rupture the lining of the stomach and cause ulcers.
HCl creates an acidic environment in the stomach for the digestion of protein.
Break down of food and killing of harmful microorganisms in food
HCl is involved in catabolism of food's into anabolism of nutrients which is the basis of metabolism.