Digestive enzymes are chemicals -- specifically, they are proteins -- that help digestive processes take place more quickly. While digestion relies largely upon stomach acid, acidic digestion by itself would be a very slow process. As such, enzymes specifically designed to assist in digesting protein, carbohydrate and fat help to speed digestion and increase its efficiency. Several different types of digestive enzymes exist, released by different glands and organs of the digestive tract.
Mouth Enzymes
While very little digestion takes place in the mouth -- in fact, most of what happens in the mouth is simply mechanical breaking of food into smaller pieces -- starch digestion begins here. An enzyme secreted in saliva called salivary amylase begins the process of digestive amylose, which is the chemical name for starch, while you are still chewing your food. As such, explain Drs. Mary Campbell and Shawn Farrell in their book "Biochemistry," starch digestion is particularly quick and efficient relative to digestion of other nutrients--proteins and fats take much longer to digest, and digestion begins later.
Stomach Enzymes
Digestion continues in the stomach, where a few enzymes assist stomach acid in breaking down foods. The two most important stomach enzymes are called gastric amylase and pepsin, notes Dr. Lauralee Sherwood in her book "Human Physiology." Like salivary amylase, gastric amylase goes to work on starch, breaking it down into its smaller chemical components, which are called glucose. Pepsin is a protease, or protein-digesting enzyme. It starts to break down proteins into their chemical constituents, which are called amino acids. Digestion of fat doesn't take place to any significant extent in the stomach.
Pancreatic Enzymes
The pancreas secretes a wealth of digestive enzymes into the small intestine, and digestion of all three nutrient types -- carbohydrates, proteins and fats -- is completed here. Pancreatic amylase completes the digestion of starch, while intestinal and pancreatic enzymes of various types digest the smaller sugar units released from carbohydrate. Pancreatic proteases completed the digestion of protein, and the intestine absorbs the amino acids. Finally, fat digestion commences with the help of pancreatic lipase, a fat-digesting enzyme, explains Dr. Sherwood. Once fats have been digested into their components, called fatty acids and monoacylglycerides, the components can be absorbed into the bloodstream.
References
- "Biochemistry"; Mary Campbell, Ph.D. and Shawn Farrell, Ph.D.; 2005
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
