Where Does Lipid Digestion Begin?

Lipid digestion begins in the mouth, where an enzyme called lingual lipase starts to emulsify, or separate, the fats. Lingual lipase is a component of saliva and is released by the salivary glands. Because lipids aren't water-soluble, they must be broken down before they can be digested and absorbed by the body.

After food is swallowed, gastric lipase enzymes in the stomach work with the motion of the digestive tract to further emulsify the fat. Bile salts from the liver prevent these emulsified drops from regrouping and returning to their previous, less digestible state.

After bile salts and pancreatic enzymes complete the digestive process in the small intestine, the component fatty acids are coated with water-soluble proteins and absorbed by the intestinal lining. Cholesterol, a hormone produced by the liver, transports these fatty acids from the intestines to the body's other cells. From there, they enter the bloodstream and are integrated into the body's tissues.

Lipid-digesting enzymes are also found outside the digestive system. In the human body, cells contain lipase-producing organelles called lysosomes, which digest the body's own lipids as part of the cellular life cycle. Animal-sourced lipases are used industrially to create vegetable oil-based fuels and to ferment cheese and yogurt. Lipases are also present in the venom of cobras and bees.