Collagen is the most abundant protein in the human body and is the substance that holds the whole body together. It is found in the bones, muscles, skin and tendons, where it forms a scaffold to provide strength and structure.1,2
Endogenously produced collagen (i.e. collagen synthesised by the body) plays numerous important roles in health, with the breakdown and depletion of the body's natural collagen associated with a number of health problems. As such, exogenous (supplemental) collagen is increasingly used for medical and cosmetic purposes, including to help with healing and repair of the body's tissues.
You will also see introductions at the end of some sections to any recent developments that have been covered by MNT's news stories. Also look out for links to information about related conditions.
Fast facts on collagen
Here are some key points about collagen. More detail and supporting information is in the main article.25-27
- Protein makes up around 20% of the body's mass, and collagen makes up around 30% of the protein in the human body.
- There are at least 16 types of collagen, but 80-90% of the collagen in the body consists of types I, II, and III.
- Type I collagen fibrils are stronger than steel (gram for gram).
- Collagen is most commonly found within the body in the skin, bones and connective tissues.
- The word "collagen" is derived from the Greek "kolla," meaning glue.
- Collagen gives the skin its strength and structure, and also plays a role in the replacement of dead skin cells.
- Collagen production declines with age (as part of intrinsic aging), and is reduced by exposure to ultraviolet light and other environmental factors (extrinsic aging).
- Collagen in medical products can be derived from human, bovine, porcine and ovine sources.
- Collagen dressings attract new skin cells to wound sites.
- Cosmetic products such as revitalizing lotions that claim to increase collagen levels are unlikely to do so, as collagen molecules are too large to be absorbed through the skin.
- Collagen production can be stimulated through the use of laser therapy and the use of all-trans retinoic acid (a form of vitamin A).
- Controllable factors that damage the production of collagen include sunlight, smoking and high sugar consumption.
What is collagen?
Collagen is a hard, insoluble and fibrous protein that makes up one-third of the protein in the human body. 3 In the majority of collagens, the molecules are packed together to form very similar long thin fibrils.4
Collagen is the most common protein found in mammals.
According to MediLexicon, collagen comprises a family of genetically distinct molecules, all of which have a unique triple helix configuration of three polypeptide subunits known as alpha-chains.5
Each chain contains around 1,000 amino acids, and usually features an amino acid sequence consisting of glycine, proline and hydroxyproline.11
There are numerous different types of collagen, at least 16 types5, but 80-90% of collagens in the body belong to types I, II and III. The collagens in the human body are strong and flexible. Type I collagen fibrils are particularly tensile, and are stronger than steel, gram for gram.
Collagen and the body1-3,6-9
Collagen is most commonly found in the skin, bones and connective tissue within the body, providing structural support, strength and a degree of elasticity (in combination with elastin). In particular, collagens can be found in the extracellular matrix - an intricate network of macromolecules that determine the physical properties of body tissues.
In the middle layer of the skin - the dermis - collagen helps form a fibrous network, upon which new cells can grow. Collagen is also required in the replacement and restoration of dead skin cells. Some collagens also function as protective coverings for delicate organs in the body such as the kidneys.
Collagen production naturally declines with age, reducing the structural integrity of the skin and leading to sagging skin, the formation of lines and wrinkles and the weakening of cartilage in joints.
Collagen is secreted by a variety of different cells, but primarily by connective tissue cells. While young, the body consistently produces collagen, but collagen synthesis begins to decline around the age of 40, with a dramatic reduction in synthesis in women after menopause. By the age of 60 there is typically a considerable decline in collagen production.
Medical uses of collagen
Collagen is resorbable (can be broken down and assimilated by the body), is functionally diverse and is naturally occurring. This means that collagen has several different medical applications and can be used with a variety of medical devices. In addition, it can be formed into compacted solids or lattice-like gels when being prepared for use, making it clinically versatile.10
Collagen that is used medically can originate from human, bovine, porcine and ovine sources.
Collagen injections can be used in cosmetic procedures to improve the contours of aging skin.
Injections of collagen can improve the contours of the skin and fill out depressions. Collagen can be used cosmetically to remove various lines and wrinkles from the face, as well as scarring (including acne), so long as the scars do not have a sharp edge.
Collagen fillers can originate from human and bovine sources.12 Use of injected collagen can be restricted in people with severe allergies, and skin tests are typically required before bovine collagen is used.
Collagen is used to fill relatively superficial defects. More extensive defects are usually filled with substances such as fat, silicone or implants.
Within wound healing, collagen attracts new skin cells to the wound site, promotes healing and provides a platform for the growth of new tissue. Collagen dressings are therefore used in order to aid the healing of certain types of wound, including:
- Chronic non-healing wounds
- Exuding wounds
- Granulating or necrotic wounds
- Partial and full-thickness wounds
- Second-degree burns
- Sites of skin donation and skin grafts
It is advised that collagen dressings are not used for third-degree burns, wounds covered in dry eschar or with patients who may be sensitive to bovine products.
Guided tissue regeneration10
Collagen-based membranes have been used in periodontal and implant therapy to promote the growth of specific types of cell. In oral surgery, barriers can be used to prevent fast-growing cells of the gingival epithelium migrating to a wound in a tooth, preserving space there for tooth cells to potentially regenerate.
The benefit of using collagen-based membranes for this purpose, in addition to collagen's healing qualities, is that they can be made to be resorbable (the body breaks down the collagen and assimilates the protein over time). This means that patients do not require a second surgical procedure to have the barrier removed.
Collagen tissue grafts from donors have been used in peripheral nerve regeneration and vascular prostheses, used in arterial reconstruction. Certain prostheses have been found to be thrombogenic - causing coagulation of the blood - but at the same time, compatible with the body of the host.
Treatment of osteoarthritis15
Collagen supplements or formulations may be beneficial in the treatment of osteoarthritis. In a number of trials, they have been found to provide some degree of pain reduction. However, in other trials, use of collagen supplements and formulations has not been found to result in any additional benefit.
A 2006 review found that collagen hydrolysate helped to significantly decrease painful symptoms of osteoarthritis while improving joint function. The supplement was well absorbed, led to collagen accumulation in cartilage, and helped to stimulate specialized cells in the joints called chondrocytes to create extracellular matrix.
Many products containing collagen, including creams and powders, claim to revitalize the skin. However, despite the marketing of these products as ways to increase the levels of collagen within the body, collagen molecules themselves are too big to be absorbed through the skin.
The benefits of these products, where they exist, are most likely attributable to their moisturising effects, but they do not strengthen the skin or directly increase collagen concentration in the skin. Such over-the-counter treatments are also not classified as drugs, meaning that there is no requirement for scientific validation of the claims made regarding their efficacy.
Increasing collagen production
The growth of collagen, elastin, and melanin can all be stimulated through laser therapy, involving intense wavelengths of light.18 This method can be used in the treatment of stretch marks.
Collagen, like all proteins, is made up of amino acids. Of these amino acids, nine are considered essential, i.e. they cannot be synthesized by the body and must be acquired through the diet.19
Other nutrients that may support collagen formation include:19
- Proline: found in egg whites, meat, cheese, soy and cabbage20
- Anthocyanidins: found in blackberries, blueberries, cherries and raspberries
- Vitamin C: found in oranges, strawberries, peppers and broccoli
- Copper: can be found in shellfish, nuts, red meat and some drinking water
- Vitamin A: found in animal-derived foods and in plant foods as beta-carotene.
What damages collagen?
There are a number of factors that can deplete the levels of collagen found within the body. Avoiding the following could keep the skin healthy for longer:
Tobacco contains chemicals that damage collagen.
- High sugar consumption: a diet high in sugar increases the rate of glycation, a process whereby sugar in the blood attaches to proteins to form new molecules called advanced glycation end products (AGEs). AGEs damage adjacent proteins and can make collagen dry, brittle, and weak.
- Smoking: many of the chemicals present in tobacco smoke damage both collagen and elastin in the skin. Nicotine also narrows the blood vessels in the outer layers of the skin, which reduces the delivery of nutrients and oxygen to the skin, compromising skin health.23
- Sunlight: Ultraviolet rays in sunlight cause collagen to break down at an increased rate, damaging collagen fibers and inducing the accumulation of abnormal elastin. Abnormal elastin leads to the production of an enzyme that can also break down collagen. This process can lead to the formation of solar scars.24
- Autoimmune disorders: Some autoimmune disorders cause antibodies to target collagen. Mutations to the genes responsible for the coding of collagen alpha-chains can affect the extracellular matrix, leading to a decrease in the amount of collagen secreted, or to the secretion of dysfunctional mutant collagen.1
Collagen levels deplete naturally over time and there is no way to prevent this intrinsic aging. However, by taking precautionary measures, it is possible to reduce extrinsic aging and protect collagen, keeping the skin, bones, muscles and joints healthy for longer.
Recent developments on collagen from MNT news
Achieving a greater understanding of the human brain is something researchers have long been striving for but have found difficult, given the organ's complexity and the challenges in studying its physiology in a living body. Now, researchers from Tufts University in Medford, MA, have created a 3D tissue model using silk protein and collagen-based gel that can mimic brain functions.
Research led by the University of Iowa has tested a "bio patch" that regenerates missing or damaged bone by inserting DNA into nano-sized particles to deliver bone-making genetic instructions directly into cells.