Bile is a complex biological product that is produced in the liver and stored in the gallbladder for eventual release into the small intestine. Bile is rich in lipids, and also contains water, electrolytes, bile acids, phospholipids, cholesterol and pigments. Once the bile is secreted into the small intestine and performs its function, the bile acids are reabsorbed in the terminal ileum, are returned to the liver and resecreted into bile. Bile serves to perform various functions.
Antimicrobial
Bile salts tend to have powerful antimicrobial properties aimed against invading microbes that enter with food. The next time you forget to wash your hands before eating, thank bile for making sure you don't get sick!
Absorption
Bile aids greatly with the process of intestinal absorption. It serves to emulsify fats into smaller molecules, thus increasing the surface area for enzymes to work on. This in turn also helps with the absorption of fat soluble vitamins such as A, D, E and K. It also serves to neutralize any leftover stomach acid that still remains in the small intestine.
Cholesterol Elimination
Bile acids are byproducts of the breakdown of cholesterol and are the major route for cholesterol elimination via their excretion in the feces. Also, they promote the excretion of cholesterol into bile by the liver; when this enters the intestine, the cholesterol can be eliminated this way as well.
Stone Prevention
Bile acids have the tendency to bind calcium ions, and thus have protective effects against the production of calcium type of gallstones and oxalate type of kidney stones.
Hemoglobin Excretion
When erythrocytes (red blood cells) die, they leave behind a product called bilirubin. This is conjugated in the liver and then enters the bile, which serves as the route of excretion into either the feces or the urine. In fact, bile byproducts give urine (urobilin) and fecal matter (stercobilin) their characteristic colors.
References
- "Sleisinger & Fordtran's Gastrointestinal and Liver Disease, 8th Edition;" Feldman; 2006
- New York Presbyterian Hospital: Biliary Overview
