Collagen (kaw-lah-jen)


Collagen is found throughout the body in connective tissues and fibrous tissues including skin, bone, cartilage, tendons, ligaments, intervertebral discs, hair, cornea, blood vessels, and the reticular fibers of most organs (67). Collagen is built from peptide chains consisting of glycine and a combination of other amino acids, most commonly proline and hydroxyproline (69). Approximately 28 different kinds of collagens exist, but five of the most common types include type I (dermis, tendons, ligaments, bone), type II (cartilage, vitreous body, nucleus pulposus), type III (skin, vessel wall, reticular fibres), type IV (basal lamina, epithelial layer of basement membranes), and type V (lung, cornea, hair, fetal membranes, bones) (67). Type X collagen may have a role in bone health (65), particularly through the mineralization of cartilage in the subchondral bone (2). Supplements may contain collagen derived from bovine, porcine, marine and other sources (69), such as eggshell membranes (58).

Main Medical Uses

Evidence supports the use of collagen in treating conditions involving joint pain (11) including osteoarthritis (6, 9, 10, 11, 17, 19, 27, 41, 44, 53, 60), activity-related joint pain (15, 43, 58, 77), and rheumatoid arthritis (5, 6, 7, 8, 22, 73, 75, 78). It may be used in treating or preventing exercise-induced injury (64), osteoporosis (38, 53), type II diabetes (79, 80), and hypertension (39, 59). Evidence also supports its use to treat brittle nail syndrome (31) and a number of dermatological applications (14), including pressure ulcers (28, 40), edematous fibrosclerotic panniculopathy (cellulite) (61), and skin aging (3, 13, 32, 37 45, 50, 52, 55, 56, 66).


Dosing and Administration

For an explanation of the classes of evidence, please see the Rating Scales for Evidence-Based Decision Support.

Adverse Effects

Collagen supplements are generally considered as safe without the common occurrence of adverse effects (14, 41). Feelings of fullness or disagreeable taste have been reported in rare cases (48). To avoid the possibility of allergic reactions, consideration of the source of collagen may be required (57).


Collagen is extracted from the skins, bones, cartilage, and tendons of animal sources using hot water (e.g. above 40 degrees Celcius (26)), creating gelatin. Enzymes can hydrolyze gelatin into collagen hydrolysate which is the main form of collagen used in dietary supplements (70). Gelatin is derived from denatured and partially hydrolyzed collagen and has a molecular weight of 100kDa (68). It can be further refined by proteinases into collagen peptides with molecular weights between 0.3-8kDa. The lower molecular weight of hydrolyzed collagen ultimately provides advantages in absorption and distribution compared to native collagen (67).

Collagen is made up of several amino acids, which may affect its absorption and bioactivity (26). Hydrolysates consist primarily of glycine (GLY), proline (PRO), hydroxyproline (HYP), glutamic acid (GLU), arginine (ARG), alanine (ALA), as well as other essential and non-essential amino acids (66), such as aspartic acid (ASP), threonine (THR), serine (SER), cysteine (CYS), valine (VAL), methionine (MET), isoleucine (ILE), leucine (LEU), tyrosine (TYR), phenylalanine (PHE), lysine (LYS), and histidine (HIS) (72).

Associated Interactions & Depletions

Despite evidence for the effectiveness of collagen supplementation in rheumatoid arthritis, some trials report no effect of bovine Type II supplementation in rheumatoid arthritis when added to existing medication (i.e.. methotrexate, hydroxychloroquine, gold sodium thio-glucose or gold sodium thiomalate, sulfasalazine, azathioprine, auranofin, D-penicillamine, or prednisone) (46). Additionally, chicken-derived Type II collagen supplementation may not maintain methotrexate’s anti-inflammatory effects (29), though it may induce fewer adverse events (78).



Similarly to other proteins, collagen hydrolysates are degraded in the digestive tract and are mostly absorbed as amino acids, dipeptides, and tripeptides (76) via the brush-border membrane using the H+-coupled peptide transporter, PEPT1. Subsequently, they enter the bloodstream by crossing the basolateral membrane (66). Ingestion in tripeptide form may improve absorption efficiency in humans (76).


The collagen hydrolysate peptide, PRO-HYP, has been shown to be distributed to the skin, cartilage, and bone marrow in its intact form, with its highest concentration in gastric and intestinal walls (36).



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 (51).


If not reabsorbed by PEPT1 and PEPT2 (36), collagen hydrolysate peptides can be excreted in the urine after ingestion (76).

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