Bile is a compound made in the liver and is stored in the gall bladder, which is a small pouch connected to the liver. Bile works to help the body digest fat and is secreted into the small intestines. One of the active components of bile is bile salts, which facilitate the digestion and absorption of fats and oils from meals.
The main function of bile salts is to aid in the absorption of fats and oils in the stomach, which is necessary due to the lack of miscibility of fats in water. Miscibility describes the ability of two substances to mix together; oils do not mix well with the otherwise water-based contents of the intestines. Instead, ingested fats band together to form large globules that are hard for the intestines to absorb.
Bile and Emulsification
Bile salts work to help break up large globules of fats in the intestinal tract, according to the University of Louisville Medical School. Bile salts are amphipathic molecules, which means that one side of them is chemically similar to water, and the other side is similar to fats and oils. As a result, these bile salts can help provide a bridge between ingested fats and oils and their watery surroundings. This allows for the creation of a substance called an emulsification, in which the lipids are dispersed into multiple little droplets in the intestines, allowing them to be absorbed by the intestinal walls. Bile salts also help fat-soluble vitamins--such as vitamins A, D, E and K--get absorbed by the intestines.
Bile salts are needed when the body ingests large quantities of fat. Consequently, the release of bile is triggered by the presence of fat in the digestive system, Colorado State University's Physiology Hypertext explains. Ingestion of fats and oils causes secretion of the hormones cholecystokinin and secretin. These hormones cause the release of bile from the gall bladder, which is where bile is stored. Cholecystokinin and secretin also stimulate the liver to make more bile.
Bile salts also provide the body with a way to dispose of excess cholesterol, Colorado State's Physiology Hypertext explains. Bile salts contain large quantities of cholesterol. When large quantities of cholesterol are ingested, they can be turned into bile salts. Normally, the majority of bile salts are re-absorbed, allowing them to be reused. However, when the body's cholesterol stores are high, bile salt re-absorption can be reduced, which causes the bile salts to be eliminated along with fecal matter. Because of the high amounts of cholesterol present in bile, this provides the body with a method of eliminating excess cholesterol so that it does not accumulate in the blood. In fact, according to the National Heart Lung and Blood Institute, this pathway is the target of a class of cholesterol-lowering drugs called bile acid sequestrants. These medications, which include colestipol and cholestyramine, bind to bile in the intestines and keep it from being re-absorbed, helping to deplete cholesterol stores within the body.
Because bile salts contain large quantities of cholesterol, they also have a role in preventing the formation of gallstones. Most gallstones are made up of cholesterol that has formed a hard solid in the liver or in the gall bladder. This can be the result of the cholesterol not being packaged in the form of bile salts, which serve as an important reservoir for the storage of cholesterol.