How Macro-Nutrients Digest, Absorp and Digest in our Body

Carbohydrates Digestion and Absorption

Starch is broken down by an enzyme from the salivary glands where it mixes in the mouth.  Then it enters the stomach and mixes with stomach’s acid and other juices.   The salivary enzyme is now deactivated by the stomach’s protein-digesting acid in the stomach.  Starch passes through into the small intestine where another enzyme is delivered by the pancreas at full speed.  Enzymes that are on intestinal wall cells split disaccharides to monosaccharides then monosaccharides enter capillaries and then delivered to the liver to convert galactose and fractures to glucose. 

Fats Digestion and Absorption

Once the food is chewed and swallowed in the mouth, it enters in the stomach.  Little digestion occurs in the stomach.  Fat is separated from the watery components and tend to float as a layer on top. Enzymes are in the water and can’t get at the fat.  Then fat enters the small intestine. The bile made by the liver is released into small intestine when digestion for fat is needed. Bile contains compound that works as emulsifier. Bile emulsifies and suspends fat droplets within the water fluids until the fat digesting enzymes can split fatty acids from their glycerol backbone.  After the emulsification, more fat is exposed to the enzyme and fat digestion begins to work. 98% of fats consumed are absorbed but it takes time to digest it.  Then in the large intestine, a small amount of cholesterol trapped in fiber exits with the feces. 

Protein Digestion and Absorption

Once protein is consumed in the mouth, the body must first break down the protein into amino acids. After the food gets chewed in the mouth, when it goes into the stomach, the stomach’s acid denatures and cleaves the protein strands into smaller pieces which means to help uncoil the protein’s tangled strands so that the stomach enzyme can attack the peptide bond.  In the small intestine, the final breakdown occurs until all pieces of protein are broken into a single, double or three amino acids by protein-enzyme from pancreas. Then the intestinal cells absorb and transfer amino acids to the blood stream.