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Ingredient review

Collagen

Description

What is it?

Collagen is used to form connective tissues, including skin, bone, cartilage, tendons, ligaments, hair, and nails, and is built from peptide chains consisting of glycine and a combination of other amino acids, most often proline and hydroxyproline. (35) The five most common types of collagen include Type I (dermis, tendon, ligaments, bone), Type II (cartilage, vitreous body, nucleus pulposus), Type III (skin, vessel wall, reticular fibers), Type IV (basal lamina, epithelial layer of basement membranes), Type V (lung, cornea, hair, fetal membranes, bones). (34) Type X collagen may have a role in bone health, (33) particularly through the mineralization of cartilage in the subchondral bone. (1) Supplements may contain collagen derived from bovine, porcine, marine, fish, and other sources, (35) such as eggshell membranes. (28)

Not be confused with: Colostrum

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Main uses

Joint pain and inflammatory disorders
Skin, bone, and tissue repair
Other cardiovascular and endocrine applications

Formulations

Form
Bioavailability
Collagen hydrolysate
Lower molecular weight increases plasma hydroxyproline concentrations more than gelatin sourced from fish skin (37)
Gelatin hydrolysate
Fish derived collagen sources seem to increase plasma amino acids to a greater extent than porcine or chicken sources. (10)(24)
This may be due to the lower relative molecular weight of derived peptides compared with other animal sources. (17)
Undenatured collagen
Lesser GI transport efficiency and digestion than hydrolyzed collagen due to lower molecular weight as shown in vitro. (9)
Used in milligram doses compared with gram doses of gelatin or collagen hydrolysate. (8)(20)(32)

Dosing & administration

Adverse effects

Collagen supplements are generally considered as safe without the common occurrence of adverse effects. (7)(19) Feelings of fullness or disagreeable taste have been reported in rare cases. (22) To avoid the possibility of allergic reactions, consideration of the source of collagen may be required. (29)

Pharmacokinetics

Absorption

  • Collagen hydrolysates are degraded in the digestive tract and are mostly absorbed as amino acids, dipeptides, and tripeptides. (40
  • Absorbed via the brush-border membrane using the H+-coupled peptide transporter, PEPT1. (5)
  • Ingestion in tripeptide form may improve absorption efficiency in humans. (40)

Distribution

  • The collagen hydrolysate peptide, PRO-HYP, is distributed to the skin, cartilage, and bone marrow in its intact form, with its highest concentration in gastric and intestinal walls. (12)

Metabolism

  • The liver metabolizes collagen peptides, though many HYP-containing peptides (some of which can be larger than tripeptides) can pass through the liver to enter systemic circulation. (25)

Excretion

  • If not reabsorbed by PEPT1 and PEPT2, (12) collagen hydrolysate peptides can be excreted in the urine after ingestion. (40)

References