Question

Why can't lipids be absorbed like carbohydrates and protein?

Answer 1

fats leave your stomach more slowly than either carbohydrates or proteins, very little fat digestion occurs in the stomach. Bile from the liver prepares fat for the breakdown by emulsifying it, making it soluble in water. Emulsification makes it easier for enzymes to break the fat into smaller pieces for digestion. In the small intestine, the pancreatic enzyme lipase splits fats into fatty acid and glycerol, which your body then absorbs.

The bulk of dietary lipid is neutral fat or triglyceride, composed of a glycerol backbone with each carbon linked to a fatty acid. Foodstuffs typically also contain phospholipids, sterols like cholesterol and many minor lipids, including fat-soluble vitamins. Finally, small intestinal contents contain lipids from sloughed epithelial cells and considerable cholesterol delivered in bile.

ABSORPTION OF LIPID

In order for the triglyceride to be absorbed, two processes must occur:

• Large aggregates of dietary triglyceride, which are virtually insoluble in an aqueous environment, must be broken down physically and held in suspension - a process called emulsification.
• Triglyceride molecules must be enzymatically digested to yield monoglyceride and fatty acids, both of which can efficiently diffuse or be transported into the enterocyte

The key players in these two transformations are bile acids and pancreatic lipase, both of which are mixed with chyme and act in the lumen of the small intestine. Bile acids are also necessary to solubilize other lipids, including cholesterol.