The Role of Bile in Digestion: A Review
The importance of bile in digestion has been known for centuries. Bile, a yellowish-green fluid produced by the liver, is essential for proper digestion and absorption of fats and fat-soluble vitamins in the small intestine. Bile functions in both the small and large intestine to emulsify, or break down, fats, allowing them to be absorbed into the bloodstream. In this review, the composition, production, and role of bile in digestion are discussed.
Composition
Bile is composed of bile salts, bile acids, cholesterol, phospholipids, and bilirubin. Bile salts, which are derived from cholesterol, are responsible for most of the emulsifying activity of bile. Bile acids are important in the digestion of fats and fat-soluble vitamins. Cholesterol and phospholipids are also important components of bile, and serve as precursors to bile salts and bile acids, respectively. Bilirubin is a breakdown product of red blood cells, and is a major component of bile.
Production
Bile is produced by the liver and stored in the gallbladder until it is needed for digestion. When fat enters the small intestine, hormones are released that stimulate the gallbladder to contract, releasing bile into the small intestine. Bile is then reabsorbed in the ileum and enters the bloodstream. It is transported back to the liver where it is stored until it is needed again.
Role
Bile is essential for the digestion and absorption of fats and fat-soluble vitamins in the small intestine. Bile salts interact with dietary lipids, such as cholesterol and triglycerides, to form micelles. These micelles are then transported to the intestinal cells, where they are broken down for absorption. Bile acids also interact with bile-soluble vitamins, such as vitamins A, D, E, and K, to enhance their absorption.
Conclusion
Bile is an essential component of digestion, playing an important role in the digestion and absorption of fats and fat-soluble vitamins in the small intestine. Bile is composed of bile salts, bile acids, cholesterol, phospholipids, and bilirubin, and is produced by the liver and stored in the gallbladder until it is needed for digestion. Bile is essential for the formation of micelles, which enable the absorption of lipids and fat-soluble vitamins into the bloodstream.
References
Chen, Y. S., & Thong, Y. H. (2016). Role of Bile in Digestion. In Bile Acids in Liver Diseases (pp. 21-32). Springer, Singapore.
Bianchini, F., Corleto, V. D., & Portincasa, P. (2020). Bile acids and their role in hepatic and extrahepatic diseases. World journal of hepatology, 12(9), 687–701. https://doi.org/10.4254/wjh.v12.i9.687
Koot, J., & Brouwer, K. (2019). Bile acids in health and disease: Function, metabolism and clinical implications. Biochimica et Biophysica Acta (BBA) – Molecular and Cell Biology of Lipids, 1864(7), 1066–1083. https://doi.org/10.1016/j.bbalip.2019.03.001