Fats are digested in a multi-step process that begins in the mouth and primarily takes place in the small intestine:
- Mouth : Digestion starts when chewing breaks food into smaller pieces, and saliva moistens it. Saliva contains enzymes like lingual lipase that begin breaking down fats
- Stomach : Gastric lipase in the stomach further breaks down triglycerides into diglycerides and fatty acids. About 30% of fats can be converted by this stage within 2-4 hours after eating
- Small Intestine : The majority of fat digestion occurs here. The liver produces bile, stored in the gallbladder, which is released into the small intestine. Bile contains bile salts and emulsifiers that break large fat globules into smaller droplets, increasing their surface area for enzyme action
- Pancreatic Enzymes : The pancreas secretes pancreatic lipase into the small intestine, which breaks down emulsified fats (triglycerides) into free fatty acids and monoglycerides
- Absorption : Fatty acids and monoglycerides form micelles with bile salts, allowing them to cross the watery mucus layer and enter intestinal epithelial cells. Inside these cells, they are reassembled into triglycerides and packaged into chylomicrons, which enter the lymphatic system and then the bloodstream for transport to body tissues
- Additional Notes : Short- and medium-chain fatty acids can be absorbed directly into the bloodstream from the intestine because they are water-soluble. Fat-soluble vitamins (A, D, E, K) rely on fat digestion and absorption
In summary, fats are chemically digested by lipase enzymes starting in the mouth and stomach, but the critical breakdown and absorption occur in the small intestine with the help of bile and pancreatic enzymes. The end products-fatty acids and monoglycerides-are absorbed and transported throughout the body for energy and cellular functions
