The Digestion of Cheese in Humans

Cheese comes in assorted flavor varieties with differing amounts of protein and fat, and it has low levels of carbohydrate. The digestion of cheese involves breaking down these macronutrients to molecules small enough for your intestines to absorb. The process occurs between your mouth and your small intestine, with help from your liver, gallbladder and pancreas.

A couple looking in the window of a cheese shop. (Image: Tay Jnr/Digital Vision/Getty Images)

Protein

The protein in cheese consists of long chains of amino acids joined together and folded into a three-dimensional structure. Digestion of cheese protein begins in the acidic environment of your stomach, where gastric juice denatures, or unfolds, the protein into a long strand. The digestive enzyme pepsin, released from the cells lining your stomach, then clips the strand into smaller protein pieces. As these move from your stomach to your small intestine, your pancreas secretes additional enzymes to digest the protein pieces into individual amino acids. The cells of your small intestine absorb the amino acids released by cheese digestion for transport to your liver and muscle tissue.

Fat

Cheese provides your diet with variable amounts of milk fat, primarily in the form of triglycerides. Triglycerides consist of three fatty acid chains attached to a glycerol backbone, and the fatty acids in cheese are predominantly saturated. In other words, the fatty acids in cheese contain high levels of hydrogen atoms bound to the carbons making up the fatty acid chain, resulting in a type of fat that is solid at room temperature. The fat in cheese you consume undergoes the bulk of its digestion once it passes through your stomach into your small intestine. Here, a substance called bile - synthesized by your liver and stored in and secreted by your gallbladder - mixes with the fat, rendering it water-soluble. Once this happens, the digestive enzyme lipase, secreted by your pancreas, clips the cheese triglycerides into glycerol and single fatty acids. These components are now small enough for absorption by your small intestine.

Carbohydrate

The small amount of carbohydrate in cheese exists primarily as sugars such as lactose, sucrose and maltose. These sugars are disaccharides, or units of two monosaccharides joined together. Digestion of cheese disaccharides occurs in your small intestine, where cells secrete specific enzymes to cleave each disaccharide into its component monosaccharides prior to absorption.

Considerations

In addition to its macronutrients, cheese contains vitamins and minerals. These nutrients, however, need no digestion as they are already small enough for your intestinal cells to absorb. A dietary component notably lacking in cheese is fiber, which, although it does not undergo digestion, contributes to your digestive health. Consuming excessive cheese without additional dietary fiber can lead to constipation.