What Is Collagen?

Collagen is a fibrous protein found in almost every tissue, including skin, blood vessels, tendons and teeth. It makes up about 30% of all the protein in the body.

It exists as strong, tough fibers between cells and is a main component of the extracellular matrix.

Collagen is especially abundant in skin, tendon and bone.

In skin, type I accounts for 80–90% of collagen and type III for 8–12%.

There are 28 types of collagen, and the main type differs by location.

Type III makes up 30–60% of skin collagen in the fetus and 10–20% in adults.

Collagen has a triple-helix structure made of three chains, with a repeating pattern of the amino acids glycine, proline and hydroxyproline.

The amount of collagen in the body is said to decrease with age. A skin study reported that an index of collagen fiber structure in the cheek dermis declines with age.

In a study of skin cells, type I procollagen produced was 82 ng/ml in people aged 18–29 and 56 ng/ml in those aged 80 and over.

Gelatin is denatured collagen. Breaking gelatin down further with enzymes produces “collagen peptides,” which are used as food ingredients. Collagen has long been used as a raw material for gelatin and glue.

Collagen that is eaten is digested into peptides and amino acids rather than absorbed as is. After oral intake, small peptides such as prolyl-hydroxyproline (Pro-Hyp) increase in the blood.

Japanese women are estimated to take in about 2 g of collagen a day from their regular diet.

In cattle and pigs, collagen is found in bones, cartilage, ligaments, tendons and skin; in fish, in the skin, tendons and swim bladder. Gelatin is also made from collagen.

Collagen used in food and ingredients comes from the bones, cartilage, ligaments, tendons and skin of cattle and pigs, and from the skin, tendons and swim bladder of fish. Its properties differ depending on the animal and body part.

Raw materials

Gelatin is made from pig skin (41%), cattle bone (29.5%), cattle hide (28.5%) and fish (1.5%).

Amino acids

Collagen is rich in proline and hydroxyproline. Their amounts tend to be higher in pig and cattle collagen and lower in fish, especially cold-water fish.

Denaturation temperature

When heated, collagen’s triple helix unwinds (denaturation). The temperature at which this happens differs by source.

Values depend on the measuring method; each table compares values measured the same way within one study.

Structure of fish collagen

Many fish have an extra “α3 chain” in type I collagen that other vertebrates lack. It has fewer heat-stabilizing Gly-Pro-Pro sequences, which is thought to be one reason fish collagen denatures at lower temperatures.

Allergy and raw-material controls

In a study using sera from fish-allergic patients, some reacted to tuna collagen; no cross-reactivity was seen between fish collagen and collagen from other animals. Imports of cattle hide and bone for gelatin and collagen are regulated in relation to BSE.