Collagen Types I, II and III Explained

"Collagen" sounds like a single ingredient, but it isn't. It's a family of proteins, and researchers have identified at least 28 distinct types in the human body. Each type has a slightly different structure and is concentrated in different tissues — skin, bone, cartilage, blood vessels, and more. The three most talked about in nutrition and supplements are types I, II, and III. Knowing what separates them helps explain why a "collagen for skin" product and a "collagen for joints" product are rarely the same thing.

Type I collagen — skin, bone and tendons

Type I is by far the most abundant collagen in the body, making up roughly 90% of the body's total collagen content. Its fibers are densely packed and extremely strong, which is why type I collagen forms the structural framework of skin, bones, tendons, ligaments, and teeth. It's the type most associated with skin firmness and elasticity, and it's the form most commonly used in collagen supplements marketed for skin and hair.

Type II collagen — cartilage and joints

Type II collagen has a looser, more open fiber structure than type I, which gives cartilage its ability to cushion and absorb impact. It is the main structural protein of cartilage — the smooth, flexible tissue that covers the ends of bones inside joints like the knees, hips, and shoulders. Because cartilage relies almost entirely on type II collagen for its structure, this is the type that matters most when the goal is joint support rather than skin appearance.

Type III collagen — blood vessels and internal organs

Type III collagen is often found alongside type I, reinforcing it. It's a major component of blood vessel walls, internal organs, and the deeper layers of skin, contributing to the elasticity and structural integrity of these tissues. It rarely appears alone in supplements — it's usually paired with type I, since the two occur together naturally in the body.

Why the "which type" question matters for joints

This is where the distinction becomes practical. A supplement built around type I collagen (or a general hydrolyzed collagen blend) mainly reflects the collagen found in skin and bone — it may support skin and connective tissue generally, but it isn't the collagen that makes up cartilage. If your goal is specifically joint comfort and cartilage support, ingredients built around type II collagen are the ones studied for that purpose, since they match the collagen actually present in joint cartilage.

• Type I: skin, bone, tendons, ligaments — the most abundant type overall.
• Type II: cartilage — the type most relevant to joint health.
• Type III: blood vessels, organs, and deeper skin — usually paired with type I.

Reading a collagen label

When comparing products, check which type(s) are listed on the label rather than assuming "collagen" means the same thing everywhere. Some products are pure type I/III blends (often marketed for skin), some are pure type II (often marketed for joints), and some combine forms in different ways. Matching the type to your goal is more useful than simply choosing the product with the highest total collagen content.

This article is for general educational purposes only and is not medical advice, a diagnosis, or a substitute for consultation with a qualified healthcare professional. Dietary supplements are not intended to diagnose, treat, cure, or prevent any disease. Consult your doctor or pharmacist before starting any supplement.