Does Protein Need To Be Digested Before It's Absorbed?

Protein is one of the three essential macronutrients in your diet, which means you need to consume foods that contain protein for your body to function properly. But for your body to use and absorb the protein from the foods you eat, it first must be digested into its smallest form, the amino acid.

Amino Acids

All proteins are made up of amino acids. However, each protein contains different amino acids in varying amounts. While your body provides some of the amino acids necessary to build the protein found in your cells, organs and muscles, some of the amino acids must come from the food you eat. These amino acids are referred to as essential amino acids. Animal products contain all of the essential amino acids, and are called complete sources of protein. Plant foods contain some of the essential amino acids, and are called incomplete sources of protein.

Mouth

Although digestion of protein does not occur in the mouth, the process of chewing starts the digestive process. Your teeth grind and crush the protein food into smaller pieces. At the same time, your salivary glands release saliva, which moistens the food. Your saliva also contains a protein that helps the food stick together, creating a bolus that eases swallowing. Once your protein food bolus is ready for swallowing, it moves into the esophagus and down into your stomach.

Stomach

Once your protein food hits your stomach, protein digestion begins. Proteins are first broken down into smaller pieces called proteases, peptones and large polypeptides. The hydrochloric acid in your stomach helps to convert pepsinogen into the enzyme pepsin. Pepsin actually digests the collagen protein in the food you eat, getting it ready for absorption. Collagen is the connective tissue that helps keep meat together. The rest of the proteins are then sent to the small intestines for continued digestion and absorption.

Small Intestines

Most of the protein in your food is digested in the duodenum of your small intestines. The duodenum is the first part of your small intestines just below your stomach. In the duodenum, trypsin, chymotrypsin and carboxypolypeptidase enzymes help break down the polypeptides that entered from the stomach into smaller proteins and amino acids. Proteolytic peptidases are additional enzymes that help break the smaller proteins into amino acids, dipeptides and tripeptides. The dipeptides and tripeptides are then hydolyzed into amino acids. These amino acids are then absorbed through the layers of your intestines and transported to your liver, where they are then distributed throughout your body to perform their necessary duties.