Type 1 and type 3 collagen are the two most abundant structural proteins in your body, and they often work together. Type 1 provides rigid strength to bones, tendons, and skin, while type 3 adds flexibility to organs and blood vessels that need to stretch. They share many of the same tissues, but their mechanical properties are distinct, and your body adjusts the ratio between them depending on what a tissue needs to do.
Type 1 Collagen: The Body’s Structural Backbone
Type 1 collagen is the most abundant protein in the human body. It forms thick, densely packed fibers that resist pulling forces, making it the primary source of mechanical strength in tissues that bear load or tension. Its fibrils are stiff structures that give tendons their durability, bones their framework, and skin its firmness.
You’ll find type 1 collagen concentrated in bone (both compact and spongy), skin, tendons, ligaments, the outer rings of spinal discs, the tough white coating of the eye (sclera), teeth (dentin), fascia, and the outer layers of internal organs. In bone specifically, type 1 collagen forms the organic scaffold that mineral crystals deposit onto. Without that collagen framework, bones would be brittle rather than resilient. This is why collagen isn’t just about skin: it’s the reason your skeleton can absorb impact without snapping.
Collagen peptide supplements appear to support this process by providing amino acid building blocks that encourage bone-forming cells to proliferate and lay down new matrix, while simultaneously discouraging the activity of cells that break bone down. The result targets both the protein scaffold and the mineral content of bone, potentially producing denser, stronger tissue.
Type 3 Collagen: Flexibility for Hollow Organs
Type 3 collagen forms thinner fibrils than type 1 and shows up in tissues that need to expand and contract. It’s a major structural component in large blood vessels, the uterus, and the bowel, all organs that must withstand repeated stretching without tearing. Gene expression studies show high levels of type 3 collagen in the gallbladder, placenta, bladder, endometrium, various parts of the gastrointestinal tract, fat tissue, heart, prostate, skin, spleen, and testes.
Beyond providing physical structure, type 3 collagen plays a role in blood clotting by interacting with platelets, and it acts as a signaling molecule during wound healing. It also influences how cells attach, move, multiply, and specialize by communicating through receptors on cell surfaces. So it’s not just scaffolding. It’s an active participant in tissue maintenance and repair.
One of its more subtle jobs is controlling fiber thickness. When type 1 and type 3 collagen appear in the same fibril, type 3 regulates the diameter, keeping fibers from growing too large. This produces a finer, more flexible network compared to fibrils made entirely of type 1.
How They Work Together in Wound Healing
The interplay between types 1 and 3 is most visible during wound repair. When you injure your skin, your body ramps up type 3 collagen production first. These thinner, more pliable fibers form a temporary matrix that fills the wound quickly and gives cells a surface to migrate across. Type 3 is sometimes called “juvenile collagen” because of this early-stage role.
As the wound matures over weeks and months, the balance shifts. Type 3 collagen is gradually replaced by type 1, which provides the mechanical stability of a healed wound. The final result is scar tissue, which is denser and stiffer than the original skin because it contains a higher proportion of type 1 collagen with less of the flexible type 3 that normal skin has.
Their Ratio Changes With Age
The proportion of type 3 collagen in your skin is highest before you’re born. Embryonic skin contains roughly 50% type 3 collagen, but that drops to about 15% during postnatal growth as type 1 takes over. This shift continues gradually throughout life, which is one reason aging skin becomes less supple. The decline in type 3 collagen means less of the fine, elastic fiber network and more of the rigid type 1 structure.
What Happens When Type 3 Collagen Is Defective
The clearest evidence for how critical type 3 collagen is comes from vascular Ehlers-Danlos syndrome (vEDS), a genetic condition caused by mutations in the gene that codes for type 3 collagen. People with vEDS have thin, translucent skin that bruises easily, and they face a serious risk of spontaneous rupture of arteries, intestines, and the uterus. Arterial rupture, 60% of which involves the aorta, is the leading cause of death in young males with the condition.
When researchers studied the tissue of affected individuals, they found reduced total collagen content and an abnormal ratio of type 3 to type 1, which produced severely malformed collagen fibrils in both skin and arterial walls. This confirms that type 3 collagen isn’t optional for vascular integrity. It’s essential for forming properly shaped, mixed-type fibrils that keep blood vessels and hollow organs from tearing under normal pressure.
Type 3 Collagen and Liver Fibrosis
Type 3 collagen also plays a role in disease. In chronic liver disease, damaged tissue triggers fibroblasts to overproduce collagen, and type 3 is one of the primary collagens deposited in fibrotic liver tissue. Over time, this excess collagen becomes heavily cross-linked, creating a stiff matrix that perpetuates the cycle of fibrosis. Researchers now use fragments of type 3 collagen in the blood as biomarkers to track how liver fibrosis is progressing or resolving, since its production and breakdown reflect the activity of the fibrotic process in real time.
Supplements Labeled Type 1 and 3
Collagen supplements marketed as “type 1 and 3” are typically hydrolyzed collagen peptides derived from bovine hide or fish skin, both of which are naturally rich in these two types. Once collagen is hydrolyzed (broken into small peptide fragments), the original triple-helix structure is lost. Your body absorbs these fragments as short amino acid chains, which then serve as raw material for collagen synthesis throughout the body. The peptides may also function as signaling molecules that stimulate your cells to produce more collagen and build new tissue matrix.
What the science does not clearly show is that taking a supplement labeled “type 1 and 3” selectively increases those specific collagen types in targeted tissues. Your body directs amino acids where they’re needed based on its own priorities, not the label on the bottle. That said, providing collagen-specific amino acids (particularly glycine, proline, and hydroxyproline) does give your body more of the building blocks it needs for collagen production generally, which supports skin, bone, tendon, and vascular health.