17.6:
Carbohydrate Digestion
The digestion of carbohydrates begins in the mouth during mastication as numerous salivary glands release enzymes like amylase, which break down starches into smaller sugars, di and trisaccharides.
When sugars reach the stomach nothing happens because amylase is inactivated in such an acidic environment. As they enter the duodenum, the remaining complex carbohydrates are digested by the enzyme pancreatic alpha-amylase. Here in the intestine, the di and trisaccharides are further broken down into monosaccharides by brush border enzymes of the intestinal microvilli. For example, the enzyme sucrase breaks down the disaccharide sucrose into glucose and fructose.
These monosaccharides are then absorbed by the intestinal epithelium for energy usage.
17.6:
Carbohydrate Digestion
Carbohydrate digestion and metabolism break down simple and complex carbohydrates from food into saccharides (i.e., sugars) for the body to use as energy. Carbohydrate digestion starts in the mouth during mastication, or chewing. The masticated carbohydrates remain intact in the stomach. Digestion resumes in the duodenum of the small intestine, where pancreatic alpha-amylase and brush border enzymes of the microvilli convert complex carbohydrates to monosaccharides. Finally, the monosaccharides are absorbed by the intestinal epithelium for energy usage.
Types of Carbohydrates
Three basic types of carbohydrates are found in the human diet: simple carbohydrates, complex carbohydrates, and fiber. Simple carbohydrates are monosaccharide molecules such as glucose, fructose, and galactose. Complex carbohydrates, on the other hand, are polysaccharides composed of long chains of glucose. Finally, fiber is a carbohydrate that is found in the cellulose of plant-based foods. It cannot be broken down by the body for energy, but it does play a vital role in healthy digestion by helping ingested food to move along the digestive system.
Suggested Reading
Hall, Mary Beth, and David R. Mertens. “A 100-Year Review: Carbohydrates—Characterization, Digestion, and Utilization.” Journal of Dairy Science 100, no. 12 (December 1, 2017): 10078–93. [Source]
Dhingra, Devinder, Mona Michael, Hradesh Rajput, and R. T. Patil. “Dietary Fibre in Foods: A Review.” Journal of Food Science and Technology 49, no. 3 (June 2012): 255–66. [Source]