Digestive enzymes break food down into small particles that are easily absorbed and used by the body. We are biologically designed to eat raw food which is loaded with enzymes. Food is meant to primarily self-digest. Studies in animals show that when they are fed raw food, their saliva contains no enzymes. This doesn't mean that enzymes aren't made by the body for other reasons.
Enzymes do far more than digest food.
He says that lack of enzymes is one of the paramount causes of premature aging, degenerative diseases and early death. He says that arthritis and other degenerative disease first appeared in the fossil record when cooked food appeared. It has been hypothesized, for example, that proteases patrol the body and look for cancer cells to destroy. When diverted into digesting excess meat they are no longer available for this vital function. Animal studies have shown this.