Enzymes play a key role in the human digestive process. These digestive enzymes, which are secreted at various points along the digestive tract, break down food so that vital nutrients can be absorbed into the bloodstream and nonessential food components can be eliminated as waste. Because of their differing chemical structures, each of the three main food categories -- carbohydrates, fats and proteins -- requires its own special set of digestive enzymes to perform these functions.
Amylase enzymes are responsible for breaking down carbohydrates, which include both starches and sugars, into components that the digestive tract can handle. Phyllis A. Balch, author of “Prescription for Nutritional Healing,” explains that amylase enzymes are present in saliva as well as in intestinal and pancreatic juices. The admonition to chew your food thoroughly makes sense, she points out, since the enzymes in saliva need time to do their job, which is the preparation of carbohydrates for the next stage in the digestive process.
Specific amylase enzymes work on certain types of carbohydrates, Balch says. Lactase breaks down lactose, the sugar found in milk and other dairy products, while sucrase breaks down sucrose, the type of sugar common to both cane and beet sugars. Maltase is the digestive enzyme that does the lion’s share of the work in breaking down maltose, the type of sugar found in such carbohydrates as grains, sweet potatoes, beer and processed foods that contain large amounts of corn syrup.
Produced primarily by the pancreas, lipase enzymes break down fats during the digestive process. In addition to the pancreatic lipase enzymes, the salivary glands and stomach produce other lipases that help to break down fat-rich foods before they reach the small intestine. To deal with the wide variety of fats encountered in the human diet, the body produces several types of lipase enzymes, each of which is designed to target specific forms of fat.
Protease enzymes, also known as proteolytic enzymes, handle the challenging job of breaking down protein-rich foods into components that can be utilised by other steps in the digestive process. Protease enzymes secreted in humans include pepsin, trypsin and chymotrypsin, according to EnzymeStuff. People who have difficulty digesting protein sometimes take such plant-based digestive enzymes as bromelain, derived from pineapples, and papain, which occurs naturally in papaya.
Cellulase is the digestive enzyme needed to break down cellulose, the fibrous material found in many plant foods that turn up on the dining room table. Although the human body does not produce cellulase, plants themselves contain this critical digestive enzyme, thus allowing humans to digest such plant-based foods.