Digestion is the process of breaking down foods and beverages into tiny particles your body can use for energy and to build and nourish cells. This process mainly happens in the group of hollow organs known as the digestive tract, which includes the mouth, esophagus, stomach and intestines. The complete digestive system, however, includes two solid organs -- the pancreas and the liver. The liver produces bile that helps digest dietary fats.
What is Bile?
Liver cells, called hepatocytes, convert cholesterol into bile acids. These bile acids then mix with more cholesterol, other lipids, electrolytes, water and the waste product produced from the breakdown of old red blood cells known as bilirubin. The liver secretes the bile through the bile ducts to the gallbladder. The gallbladder functions as a holding chamber, keeping the bile until partially digested food enters the small intestine.
Bile acids are unique because they have one face that is hydrophobic, meaning it can mix with fats, and one face that is hydrophilic, meaning it can mix with water. As the bile enters the small intestine it mixes with the fat particles in the partially digested food. The bile breaks apart the fat globules into minute fat droplets that float in the watery intestine contents. The way bile acts on dietary fat is similar to how a detergent breaks apart grease. Enzymes produced by the pancreas and the small intestine can then digest the tiny fat droplets into fatty acids your body can absorb and use.
In addition to aiding in dietary fat digestion, the liver helps break down and eliminate cholesterol. Cholesterol is a fat-like substance found in foods that come from animals, like meat and milk, and produced by cells in your body. Although cholesterol fulfills important functions, like promoting the production of some hormones and providing structure to cell membranes, too much cholesterol can become harmful. Bile production in the liver is a major route for cholesterol elimination, according to Colorado State University.
The role of the liver in breaking down fat and cholesterol is important to maintaining your health. Fat serves as an important source of energy. Each gram of fat provides your body with nine calories. The absorption of certain nutrients also depends upon the digestion and absorption of fat molecules. The cells lining the small intestine can only absorb vitamins A, D, K and E in the presence of fat. By using cholesterol to produce bile, your liver helps regulate your blood cholesterol level to prevent high cholesterol that can lead to heart disease.
- Lucile Packard Children’s Hospital: How the Liver Works
- National Digestive Diseases Information Clearinghouse: Your Digestive System and How It Works
- Texas A&M University: Digestive System
- Colorado State University: Secretion of Bile and the Role of Bile Acids in Digestion
- USDA Dietary Guidelines for Americans 2010: Chapter 2 – Balancing Calorie Needs
- American Heart Association: Why Cholesterol Matters
- Genetics Home Reference Glossary: Fat-soluble Vitamins
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