With the digestion fat, it must initially be dissolved into the watery content of the intestine. The bile acids produced by the liver dissolve fat into tiny droplets and allow pancreatic and intestinal enzymes to break the large fat molecules into smaller ones. Some of these small molecules are fatty acids and cholesterol. The bile acids combine with the fatty acids and cholesterol and help these molecules move into the cells of the mucosa. In these cells the small molecules are formed back into large ones, most of which pass into vessels called lymphatics near the intestine. These small vessels carry the reformed fat to the veins of the chest, and the blood carries the fat to storage depots in different parts of the body.
Foods such as meat, eggs, and beans consist of giant molecules of protein that must be digested by enzymes before they can be used to build and repair body tissues. An enzyme in the juice of the stomach starts the digestion, then in the small intestine, several enzymes from the pancreatic juice and the lining of the intestine complete the breakdown of huge protein molecules into small molecules called amino acids. These small molecules can be absorbed through the small intestine into the blood and then be carried to all parts of the body to build the walls and other parts of cells.
Carbohydrates are broken into simpler molecules by enzymes in the saliva, in juice produced by the pancreas, and in the lining of the small intestine. Starch is digested in two steps. First, an enzyme in the saliva and pancreatic juice breaks the starch into molecules called maltose. Then an enzyme in the lining of the small intestine splits the maltose into glucose molecules that can be absorbed into the blood. Glucose is carried through the bloodstream to the liver, where it is stored or used to provide energy for the work of the body.
The good fats are monounsaturated fats or polyunsaturated fats that you find in healthy lean meats, plants, nuts, and olive oil. The fats considered bad for your system are the saturated fats or transfats that are found in pastries, cheeses, butter, and whole milk. Trans-fatty acids are polyunsaturated oils hardened by hydrogenation and are in such foods as fried chicken, doughnuts, which are considered unhealthy for our systems. The trans-fatty acids in these foods raise our lipoprotein; our bad cholesterol levels and increases the risk of Cardiovascular Disease and stroke (Sizer & Whitney, 2011).
National Digestive Diseases Information Clearinghouse (2011). Diabetes and Digestive and Kidney
Diseases, Retrieved Nov. 21, 2011 from: http://digestive.niddk.nih.gov/ddiseyrdases/pubs/d/
Sizer, F. & Whitney, E. (2011). Nutrition: Concepts and Controversies (12th ed.). Mason, OH: Cengage
Learning
