Digestive enzymes are specialized forms of protein that help your body break down, or digest, food for absorption into your bloodstream. Carbohydrates are substances in your diet that provide much of the energy needed to power your basic functions. Specific enzymes in your mouth and small intestine break carbohydrates down into simple forms that your body can readily absorb.
Carbohydrate Basics
Carbohydrates come in two main digestible forms called complex carbohydrates and sugars. Complex carbohydrates are also sometimes referred to as starches. Foods that contain starches include peas, corn, bread, potatoes, grains, dry beans and cereals. Types of sugar include lactose, dextrose, fructose and sucrose. Foods that contain sugars include fruits, dairy products and certain vegetables. Another form of carbohydrate, called fiber, is not digestible--it passes through the gastrointestinal tract and exits your body in your feces.
Starch Digestion
Undigested complex carbohydrates, or starches, are formed on long molecule chains called polysaccharides. When you eat, glands in your mouth produce the liquid called saliva, which contains an enzyme called amylase. In turn, amylase produces a chemical reaction that breaks the bonds in polysaccharide starch chains and creates a shorter-chain sugar called maltose. Maltose passes unaltered through your esophagus and stomach, then enters the upper portion of your small intestine. There, amylase from your pancreas gland breaks down any polysaccharide bonds left intact after contact with your saliva.
Sugar Digestion
The lining of your small intestine secretes juices that contain another enzyme called maltase. Maltase breaks down molecules of maltose and leaves behind molecules of the very simple sugar called glucose. Sugars in your diet are smaller than starches and don't get digested until they come into contact with other secretions from your small intestine. For example, the sugar sucrose gets broken down by an enzyme called sucrase, which leaves behind glucose and another sugar called fructose. The sugar lactose, also called milk sugar, gets broken down by an enzyme called lactase, which leaves behind glucose and a sugar called galactose.
Absorption and Fiber Passage
After carbohydrate digestion, the remaining simple sugars in your small intestine are absorbed through specialized openings in the intestinal wall and passed into your bloodstream. Once inside your bloodstream, glucose in particular gets used as a main energy source for cells throughout your body. A form of indigestible carbohydrate called insoluble fiber passes through your gastrointestinal system without getting broken down by enzymes and leaves your body virtually unaltered. Another form of indigestible carbohydrate called soluble fiber is also unaffected by enzymes. However, it dissolves in the presence of water and takes on a gel-like consistency as it passes through your system.
References
- Elmhurst College - Virtual Chembook: Roles of Enzymes in Biochemical Reactions; Charles E. Ophardt; 2003
- National Digestive Diseases Information Clearinghouse: Your Digestive System and How It Works; April 2008
- Biology Online: Digestive Enzymes
- Centers for Disease Control and Prevention: Nutrition for Everyone; Carbohydrates
