Collagen is a crucial protein that helps your body support many of its structures, such as tendons, ligaments, eyes, and skin. Divided into 28 types, collagens can be some of the most beneficial elements to prevent aging signs like wrinkles.
However, understanding what each of these 28 different collagen types does can be a challenging experience. Furthermore, knowing their individual functions can help diagnose specific diseases. Here’s what you need to know.
What Is Collagen?
Collagen is a protein that is the building block for many of your body’s structures, including your skin, bones, and tendons. Accounting for about 30% of your body’s proteins, collagen is also present in your organs and blood vessels (1).
Currently, experts have identified 28 different types of collagens. These are categorized according to their composition, function, and location in your body. Although the first five are the most common, here’s a brief description of each of them (1):
Collagen Type I
Type I collagen is, by far, the most abundant collagen in your body. It accounts for 90% of your total collagen and is crucial in forming connective and load-bearing tissues. For example, it provides ligaments and tendons with their mechanical ability to support your weight (2).
Collagen I’s presence in tendons and ligaments has earned it the top place in a sub-classification called “fibril-forming collagens.” Furthermore, it’s also vital in forming basal membranes, skin, and blood vessels (3).
Collagen Type II
Type II collagen also forms part of the fibril-forming sub-group, as it’s present in structures such as tendons, skin, and ligaments. Yet, it serves a different function, as it is only found in two zones out of the four that make up those ligamentous structures (3).
Mainly, it’s prevalent in the second zone, known as “fibrocartilage.” This zone provides load-bearing mechanical properties to tendons and ligaments. However, it’s also present in the third zone, which is also called fibrocartilage — but closer to the bone (3, 4).
Collagen Type III
Collagen type III is found along with type II in the fibrocartilage zone, although in fewer amounts. However, it’s also a crucial component in your bowel, uterus, and blood vessels. Furthermore, collagen type III is vital in wound healing, as it’s involved in the blood-clotting process (3, 5).
Mutations in the gene related to collagen type III result in severe conditions such as Ehlers-Danlos syndrome. This condition makes your joints and skin exceptionally fragile and flexible, along with causing sudden ruptures in your blood vessels or intestines (5, 6).
Collagen Type IV
Collagen type IV forms part of a specific cellular structure called the “basement membrane.” Found beneath the cells of your organ’s tissues and your skin, the basement membrane provides structure and protects the cells it’s attached to. For example, it forms a barrier to prevent the spread of cancer and tumors (7).
Surprisingly, and unlike most other collagens, type IV collagen is exclusively present on basement membranes. There, it forms a polygonal mesh (often referred to as a “chicken-wire network”) that provides support to the membranes (7).
Collagen Type V
Type V collagen is another fibril-forming group member present in most of your body’s connective tissues. Like the other similarly-classified collagens, it’s found in tendons and ligaments — but in smaller quantities (3, 8).
This collagen can, like type III, cause conditions like Ehlers-Danlos syndrome when the gene is not functioning correctly. Furthermore, an excess of this gene’s activity can lead to cancer and fibrosis (8).
Collagen Type VI
Type VI collagen is another prevalent collagen in connective tissue, although it plays a different role than the previous types. Mainly, it’s involved in repair and maintenance processes within the cells, along with developing specific extra-cellular structures (3).
Also, collagen type VI has shown to be crucial to the musculoskeletal system. However, how it impacts it is still unclear. A lack of collagen VI could lead to severe conditions like muscular dystrophy, which causes a gradual loss of the muscles’ force (9, 10).
Collagen Type VII
Type VII collagen is crucial to the skin, as it attaches the epidermis to the dermis — meaning that it rivets the outer layer of skin to the middle one. Unsurprisingly, it achieves this through the basement membranes between those two layers (11).
A lack of type VII collagen is the cause of a severe condition called dystrophic epidermolysis bullosa. Like Ehlers-Danlos syndrome, this condition causes skin fragility and scar-related problems (12).
Collagen Type VIII
Collagen Type VIII is rarely found in the musculoskeletal system — instead, it forms hexagonal networks in Descemet’s membrane. This is a special basement membrane found beneath your eyes’ cornea (3, 13).
But this type of collagen can also appear in hypertrophic cartilage, which appears after bone lesions. For example, after a fracture, the body will start to heal by growing hypertrophic cartilage in a similar shape to the injured bone. Then, it will slowly replace it with actual bone (14, 15).
Collagen Type IX
Type IX collagen is associated with hyaline cartilage — the most common type of cartilage in your body. Hyaline cartilage is also known as “articular cartilage,” as it’s most often found at the end of your bones to form joints (16, 17).
Collagen type IX is the first of the sub-group known as “FACIT.” These collagens are involved in forming fibrils, making them essential to the load-bearing properties of your joints, tendons, and ligaments, among other structures (3).
Collagen Type X
Collagen Type X is related to collagen VIII, as they serve similar functions. However, the key difference is that collagen X isn’t prevalent in the body — in fact, it’s only present in hypertrophic cartilage (3).
As we already mentioned, hypertrophic cartilage is crucial to the healing process of injuries like bone fractures. When the gene related to collagen X doesn’t work correctly, it could result in conditions like Schmid metaphyseal chondrodysplasia — which causes short stature (18).
Collagen Type XI
Collagen Type XI is present in tendons and ligaments, making it part of the fibril-forming collagens. Yet, it’s found in much lower quantities than the other collagens and usually acts as a complement for types I, II, and III (3).
Types XI and V are crucial to assembling fibrils in your body’s tendons and other supportive structures. Plus, they also play a key part in organizing them during the growth and development of tissue structures (19).
Collagen Type XII
As a FACIT collagen, type XII is essential in forming fibrils that make up your tendons, ligaments, and other supporting structures. Type XII collagen is found at most stages of development, making it essential for correctly forming your body (3).
Besides helping in assembling, packing, and stabilizing tendon fibrils, type XII is also present in the cornea. Furthermore, collagen type XII is also involved in bone growth by maintaining a network among specific cells (20, 21).
Collagen Type XIII
Type XIII collagen forms part of a sub-group called “transmembrane collagens.” These collagens act as connectors between intracellular and extracellular components that are key to the correct development of the musculoskeletal system (22).
Collagen type XIII is also crucial for developing your heart and neural structures. Like most other collagens, a deficiency of type XIII can lead to several conditions. For example, experts suggest that lacking this collagen leads to neuromuscular junction disorders (22).
Collagen Type XIV
Collagen type XIV is another FACIT collagen, meaning that it helps assemble and stabilize the fibrils in your ligaments, tendons, and other connective structures. However, type XIV is mainly found in the entheses — the zone where a specific tendon connects with a bone (3).
Collagen type XIV is also present throughout the rest of the connective tissues. Mainly, it maintains the integrity and mechanical properties of the tissue. This makes it crucial for providing the load-bearing capabilities of tendons and ligaments (23).
Collagen Type XV
Type XV collagen forms part of a sub-group known as “multi-plexins” — collagens related to the basement membranes. It plays a crucial role in maintaining the matrix that connects cells while also preventing tumors (24).
Although there isn’t a specific set of conditions linked to a type XV deficiency, experts believe that it could lead to several defects. Particularly, it could cause cardiovascular defects and skeletal myopathy (24).
Collagen Type XVI
Type XVI collagen is part of a sub-group called “FACIT-like” due to certain features similar to the FACIT collagens. However, these FACIT-like collagens have different and unique structures and functions (3).
Unlike other collagens, FACIT-like ones haven’t been studied enough to know their exact functions. Yet, research suggests that they help stabilize collagen fibrils and mediate communication between cells (23).
Collagen Type XVII
Type XVII collagen is crucial to communication between components that are inside and outside the cells. As such, they form part of the “trans-membrane” collagens — which are key to the proper growth and development of your bones and muscles (3).
Collagen type XVII abnormalities are closely linked to several types of cancer, including lung, breast, and cervical cancer. Similarly, a specific gene mutation related to this collagen is the leading cause of epithelial recurrent erosion dystrophy (24, 25).
Collagen Type XVIII
Type XVIII collagen is found in most tissues, from tendons to ligaments. As part of the multi-plexins, it’s related to the basement membranes and helps connect cells. It also helps regulate renal inflammation and retinal growth (26).
Mutations in the gene related to collagen type XVIII result in a rare condition known as Knobloch syndrome. This condition leads to blindness, skull deformities, and several eye problems (26).
Collagen Type XIX
Collagen type XIX is another member of the FACIT-like subgroup, which helps support the matrix that connects cells. However, the other functions of collagen type XIX are still unknown — but research suggests that it’s more active during the embryonic stage (27).
Abnormalities relating to type XIX collagen are closely liked to amyotrophic lateral sclerosis (ALS). This rare condition leads to degeneration and eventual death of the motor neurons, often leading to paralyzation and cognitive impairment (27).
Collagen Type XX
Collagen type XX is a relatively unexplored collagen that forms part of the FACIT categorization. Experts believe that type XX collagen is primarily present in the brain, testicle, and spleen tissues (28).
The main interest of collagen type XX is its involvement in brain cancer. According to recent research, an excess of activity in the gene related to type XX is closely linked to this cancer, along with others like prostate cancer (28).
Collagen Type XXI
Type XXI collagen is another member of the FACIT-like subgroup, along with types XVI, XIX, and XXII. It’s present in the heart, placenta, kidney, lung, and pancreas, among other organs. Curiously, it’s one of the few collagens that aren’t vulnerable to genetic mutations (29).
Although more research is needed, experts suggest that type XXI collagen may be involved in blood vessel assembly. Similarly, it may also interact with type I collagen to maintain the extra-cellular matrix (29).
Collagen Type XXII
Collagen type XXII that’s mostly present in your heart and skeletal muscles. Part of the FACIT-like collagens, type XXII is essential in supporting the network between cells. This collagen may also be found in cartilage and skin — but more research is needed to confirm these claims fully (30).
Type XXII collagen may also act as a stabilizer while also contributing to the maintenance of muscle attachments in tendons and ligaments. An elevated level of collagen type XXII may be a sign of different types of cancer (30).
Collagen Type XXIII
Type XXIII collagen is a trans-membrane collagen that’s found in the lungs, cornea, skin, and tendons. Unfortunately, like some other unexplored collagens, its function is still unknown — although research suggests that it’s involved in cell-to-cell communication (31).
Experts point out that this collagen may be a valuable diagnostic tool for a specific kind of cancer. This is because high levels of collagen type XXIII have been found in urine samples in lung cancer patients (31).
Collagen Type XXIV
Type XXIV collagen is prevalent in bone formation — especially during the newborn stage. Yet, this collagen is also found in the brain, muscles, kidneys, spleen, liver, lungs, testicles, and ovaries (32).
Besides its involvement in bone formation, the other roles of type XXIV are currently unknown. However, experts still group it under the fibril-forming collagens subclassification. It’s also not linked to any specific mutation or condition (3, 32).
Collagen Type XXV
Collagen type XXV is a member of the multi-plexin collagens due to its involvement in the network that connects cells. It’s mostly found in the brain neurons — although it’s also present in the heart, testicles, and eyes (3, 33).
Due to its involvement with the brain, an excess of collagen type XXV is closely linked to the development of Alzheimer’s disease. Furthermore, this collagen may be related to antisocial personality disorder and congenital cranial dysinnervation disorder (33).
Collagen Type XXVI
Type XXVI collagen is one of the two collagens that can’t be categorized in the previously mentioned sub-groups. Mostly, it’s found on the testicles and ovaries, where it plays a crucial part in tissue modeling and generation (34).
Type XXVI is one of the least researched collagens, with no mutations associated with its related gene. However, experts suggest it’s most active during the early development of the genitals (34).
Collagen Type XXVII
Collagen type XXVII is the last member of the fibril-forming collagens. However, it differs from the rest of the collagens in structure and function. Collagen XXVII is primarily present in cartilage (35).
Type XXVII collagen is also present during the early stages of bone development. As such, a mutation in its related gene causes a condition called Steele syndrome. This condition leads to short stature. scoliosis, and dislocated hips, among other things (35).
Collagen Type XXVIII
The final collagen, type XXVIII, is also hard to categorize in the traditional collagen sub-groups. Mostly, it’s present in the skin, musculoskeletal system, and lungs. Plus, it’s found in the heart, liver, adrenal gland, gallbladder, pancreas, and esophagus (36).
No mutations or conditions are currently linked to collagen type XXVIII. However, initial research suggests that it may be linked to Charcot–Marie–Tooth disease — a genetic disorder that causes nerve damage (36, 37).
How Can I Tell if I’m Missing Collagen?
Unfortunately, collagen levels can’t be measured in a direct way, like a blood test. However, keeping an eye out for the following signs can help you detect when you’re lacking collagen (1):
- Wrinkled or saggy skin
- Blood flow problems
- Weakened muscles
- Hallow eyes and face
- Loss of flexibility in tendons and other connective tissues
As you may have noticed, these signs are the same symptoms that usually appear during aging. This is because the older you get, the less collagen your body produces. At the same time, it breaks down currently-existing collagen at a faster rate (1).
Smoking is also a risk for collagen damage, as it reduces its production. Similarly, it harms your blood vessels’ ability to deliver nutrients and oxygen to your skin. Long-term smoking may cause wrinkles and an impaired wound-healing process (1).
Another risk factor for collagen production is exposure to direct sunlight. Ultraviolet light can reduce collagen production and break-down rates, causing collagen-related problems such as wrinkles.
Related: Can you take too much collagen?
Can I Increase my Collagen Levels Through my Diet?
Although collagen can’t be absorbed directly through foods, there are some ways you can support your collagen production through your diet. Essentially, a healthy diet should ensure a good amount of the raw ingredients needed for creating collagen. These are some of the necessary elements for producing collagen:
- Vitamin C
Ensuring that your diet is rich in these elements will help your body maintain a healthy collagen balance. For example, oranges and strawberries are rich in vitamin C, while nuts and leafy greens are great copper sources.
However, evidence suggests that you can promote collagen production by ingesting collagen peptides — more commonly known as “collagen supplements.”
Key Takeaways: Types of Collagen
Collagen is a protein essential for forming connective tissues that also plays a vital role in wound healing. Each type of collagen has a specific function and is found in different locations in the body.
There are 28 types of collagen, which are categorized according to their composition, function, and location in your body. The most common types are collagen I, II, III, V, and VI. Type I collagen is the most abundant collagen in your body and is crucial for forming connective and load-bearing tissues.