Collagen often gets hyped in the beauty and supplement aisles, but it’s much more than just a “skin protein.” It’s the most abundant protein in the human body, making up about a third of all protein mass. Collagen acts like scaffolding—holding together skin, cartilage, bones, blood vessels, and even parts of the digestive system. Without it, tissues lose their shape, strength, and ability to repair themselves.
So far, scientists have identified at least 28 distinct types of collagen, but most of the structural support in your body comes from just a handful: Types I, II, III, IV, V, and X. Each has unique roles, and understanding the differences can help you choose better supplements—or at least appreciate the complexity of the tissues that keep you moving, healing, and aging (hopefully gracefully).
Type I Collagen: The Skin and Bone Builder
Where it’s found: Skin, bones, tendons, ligaments, and teeth.
Why it matters: Type I makes up about 90% of your body’s collagen. It’s what gives your skin strength and your bones resilience.
Research has consistently shown that Type I collagen peptides can improve skin elasticity and hydration, particularly in middle-aged women. A review found that daily collagen supplementation significantly improved skin hydration and elasticity compared to placebo. Type I is also heavily studied in bone health: a clinical trial reported that postmenopausal women taking collagen peptides had improved bone mineral density after 12 months.
Takeaway: If your priority is skin and bone health, Type I is the backbone (literally) of collagen supplementation.
Type II Collagen: Joint Protector
Where it’s found: Cartilage.
Why it matters: Cartilage cushions your joints. Without strong collagen support, it wears down, leading to stiffness, inflammation, and arthritis.
A randomized controlled trial found that adults with knee osteoarthritis who took Type II collagen had significantly less pain and better joint function than placebo groups. Unlike Type I, which focuses on skin and bone, Type II is the go-to for joint support—especially in athletes or people with arthritis.
Takeaway: For knees, hips, and mobility, Type II is the type to look for.
Type III Collagen: Vessel and Organ Support
Where it’s found: Skin, blood vessels, intestines, and internal organs.
Why it matters: Type III works hand-in-hand with Type I, but it’s especially important for blood vessels and internal tissue integrity.
Declines in Type III with age contribute to wrinkling, but also to weaker blood vessels and reduced elasticity in arteries. In fact, genetic defects in Type III collagen cause vascular Ehlers–Danlos syndrome, a condition marked by fragile blood vessels.
Takeaway: If you’re thinking beyond skin and joints to circulatory and gut health, Type III matters.
Type IV Collagen: The Barrier Builder
Where it’s found: Basement membranes (thin layers that separate and protect tissues, like skin from deeper layers, or kidneys from blood vessels).
Why it matters: Type IV acts as a filter and protective shield. In kidneys, it helps filter blood to form urine. In skin, it anchors the outer layer (epidermis) to underlying tissue.
Defects in Type IV collagen are linked to Alport syndrome, a genetic condition that causes kidney disease and hearing loss.
Takeaway: While you won’t find Type IV in supplements, it’s a reminder that collagen’s role goes far beyond skin creams—it’s essential to your body’s filtration systems.
Type V Collagen: The Fibril Organizer
Where it’s found: Cornea of the eye, hair, placenta, and alongside Type I fibers.
Why it matters: Type V helps regulate the size and assembly of collagen fibers, especially in skin and connective tissue. It’s also essential for eye health—without it, the cornea loses transparency.
A study showed that defects in Type V collagen lead to abnormal corneal structure. It also plays a role in pregnancy: proper development of the placenta relies heavily on this type.
Takeaway: Type V may not headline supplement labels, but it’s crucial for eye integrity, reproductive health, and collagen organization overall.
Type X Collagen: The Bone Growth Specialist
Where it’s found: Growth plates in bones (where new bone forms during growth).
Why it matters: Type X is essential for bone formation and repair. It regulates mineralization in cartilage that turns into bone—a process especially critical during adolescence.
Mutations in Type X collagen genes cause Schmid metaphyseal chondrodysplasia, a rare skeletal disorder. More broadly, researchers study it in relation to fracture healing. A study highlighted how Type X expression spikes during bone repair, suggesting therapeutic potential.
Hydrolyzed Collagen: Making It Usable
When people buy collagen powders or gummies, they’re usually getting hydrolyzed collagen (also called collagen peptides). This means the protein has been broken into smaller chains that the digestive system can absorb more easily.
Meta-analyses show that hydrolyzed collagen supplementation can improve skin elasticity, hydration, and dermal collagen density. Other studies suggest it can also improve joint pain and even gut barrier integrity—though research on gut health is still emerging.
Choosing the Right Collagen for You
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For skin & bones: Look for Type I (or blends that include it).
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For joints & mobility: Type II is best studied.
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For gut & vascular health: Type III (often found in blends).
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For specialized health (like eyes or growth): Types IV, V, and X remind us that collagen is more than a cosmetic buzzword—it’s fundamental biology.
Final Thoughts
Collagen isn’t just one thing—it’s a family of proteins with at least 28 identified members. Most supplements focus on Types I, II, and III, but research into other types is deepening our understanding of how collagen supports tissues we rarely think about—like kidneys, eyes, and even growth plates in bones.
The science is evolving quickly. If you’re thinking of adding collagen to your daily routine, it’s worth considering not just the marketing claims but the actual type and purpose. Whether you’re interested in supporting skin, joints, or overall healthy aging, collagen’s diversity gives you options—and a deeper appreciation for the biology holding you together.
