What Is Collagen? A Guide to the Protein Family Behind a Popular Beauty and Wellness Ingredient

By Nick Ouzounov, PhD, Co-Founder and CTO, Geltor

If you could zoom in on your body and look past your cells, you’d find a vast, woven scaffold underneath. It holds your skin taut, lets your tendons pull on bone without snapping, cushions your joints, and gives your blood vessels the strength to withstand a lifetime of heartbeats. That scaffold is made largely of one family of proteins: collagen.

Collagen shows up on a lot of labels, from serums and creams to powders, gummies, and drinks, usually described as if everyone knows and agrees about what it is. What most of those labels leave out is that collagen isn’t a single ingredient. It’s a family name, the way “citrus” is a family name: it tells you about as much as “citrus” tells you about the difference between a lemon and a grapefruit. Knowing which collagen a product uses can indicate what you can expect from it.

How Many Types of Collagen Are There?

Your body makes at least 28 different types of collagen, numbered, not very romantically, type 1 through type 28 [1]. Each is built to its own design, for its own job. For example, Type 1 is the thick rope that gives skin and tendon their strength. Type 2 forms the netting in cartilage that holds a waterlogged gel in place, and it’s that trapped water, squeezed and released as you move, that does the actual cushioning [2]. Type 4 doesn’t rope at all; it links edge to edge into a thin sheet instead. Other types are so scarce you’d struggle to find them in a tissue sample, and they still matter, a lot.

Even 28 undersells it. A “type” isn’t a single protein; every collagen molecule is three strands wound together, each strand from its own gene, and most of those genes can be read more than one way [1,3]. Once you count the variants, the protein database UniProt lists more than 100 distinct human collagen proteins and isoforms [4]. That’s a striking number to sit beside a jar of face cream labeled simply “collagen.”

So, when a label, headline, or study says “collagen,” the honest first question is which type? And the honest answer is usually a mix, with Type 1 making up most of it. That’s not because Type 1 is the only collagen that matters. It’s because Type 1 is the most abundant collagen in the body, and abundance is what makes something easy to extract [1].

The table below is a high-level summary of the 28 identified collagen types found in animals. Each belongs to a broader family, leans structural or signaling (it’s a spectrum), its key role, and roughly how abundant it is in an animal.

Type	Category	Structural / Signaling	What It Does	How Common
I	Fibril-forming	Structural	Main structural rope of skin, tendon, and bone; the body’s most abundant collagen	Abundant
II	Fibril-forming	Structural	Builds the fibril network in cartilage that holds cushioning water in place	Abundant in cartilage; scarce elsewhere
III	Fibril-forming	Structural	Co-assembles with Type I in skin and blood vessels; dominant in early wound healing	Abundant (2nd most common in skin)
IV	Network-forming	Structural	Forms the sheet-like basement membrane beneath skin and other tissue layers	Moderate, widespread
V	Fibril-forming (minor)	Structural	Regulates the diameter of Type I fibrils; found in cornea, bone, and placenta	Minor
VI	Microfibril-forming	Structural + signaling	Forms beaded microfilaments around cells; helps anchor cells to the matrix	Minor
VII	Anchoring fibril	Structural	Anchors the epidermis to the dermis	Extremely rare (~0.001% of skin collagen)
VIII	Network-forming (short-chain)	Structural	Component of the cornea’s Descemet’s membrane and some vascular tissue	Minor
IX	FACIT	Structural + signaling	Attaches to Type II fibrils, helping organize the cartilage network	~1% of adult cartilage collagen
X	Short-chain	Structural	Forms a network during cartilage-to-bone mineralization in the growth plate	Minor, developmental
XI	Fibril-forming (minor)	Structural	Co-assembles with Type II to regulate cartilage fibril diameter	Minor
XII	FACIT	Signaling	Organizes Type I fibrils in tendon, ligament, and cornea	Minor
XIII	Transmembrane	Signaling	Membrane-anchored; involved in cell adhesion and neuromuscular junctions	Rare
XIV	FACIT	Signaling	Similar to Type XII; concentrated where tendon meets bone	Minor
XV	Multiplexin	Structural + signaling	Supports basement membrane integrity in muscle and blood vessels	Minor
XVI	FACIT	Signaling	Found in skin, cartilage, and smooth muscle; organizes microfibril networks	Minor
XVII	Transmembrane	Structural + signaling	Anchors skin’s epidermis to its basement membrane; linked to hair follicle stem cells	Minor
XVIII	Multiplexin	Signaling	Cleaved to release endostatin, a fragment that regulates blood vessel growth	Minor
XIX	FACIT	Signaling	Found near muscle basement membranes; role in muscle cell differentiation	Rare
XX	FACIT	Structural	Found in cornea and cartilage; still not well studied	Rare, limited data
XXI	FACIT	Signaling	Found in skin and blood vessels; rises with tissue remodeling (more in our next piece)	Rare
XXII	FACIT	Signaling	Found at tissue junctions: myotendinous junctions, hair follicles, cartilage-synovium boundaries	Rare
XXIII	Transmembrane	Signaling	Found in some epithelial tissue; involved in cell adhesion	Rare, limited data
XXIV	Fibril-forming (minor)	Structural	Involved in bone development and osteoblast collagen assembly	Rare
XXV	Transmembrane	Signaling	Primarily neuronal; studied for its role in amyloid plaque formation	Rare
XXVI	Other	Not well characterized	Found in testis and ovary tissue	Rare, poorly characterized
XXVII	Fibril-forming (minor)	Structural	Organizes the pericellular matrix in the cartilage growth plate	Rare
XXVIII	Other	Not well characterized	Found in peripheral nerve tissue	Rare, poorly characterized

Classification and tissue roles synthesized from Ricard-Blum (2011) [1] and Ricard-Blum & Ruggiero (2005) [9]; splice-variant count from UniProt (2025) [4]. Type XXI is explored in depth in our next piece.

Structural vs. Signaling Collagen

Once you sort the family by function instead of by number, a pattern emerges. Every collagen does some combination of two things: holding tissue together (structural), and passing along information (signal). Individual types just lean one way or the other [1].

The structural types are the builders, ones you’ve likely heard of. Types 1 and 3 do most of the structural work in skin; these are the thick, load-bearing fibers that keep it firm and are commonly referred to as “collagen” in a beauty context. The signalers are less famous, far less abundant, but arguably the most interesting. Instead of forming fibers of their own, many attach to the surface of the big structural types, sitting exactly where the scaffolding meets living cells [1,9]. Very little mechanical strain passes through them; instead, its position enables information exchange.

The collagen category is dynamic; its signaling function carries receptors that physically grip onto other collagens, and what they feel through that grip changes how they behave, whether they stay put or move, divide, or start repairing [8]. For most of the last century, collagen was treated as scaffolding and nothing else. But that’s just the beginning.

None of this is a clean split. Type 1, the ultimate builder, is also one of the collagens your body reaches for first when you’re injured. But knowing where a collagen sits on the builder-to-signaler spectrum tells you a lot about what it’s likely to be for.

What Makes Something Collagen?

There is a lot of discussion on the definition of “real collagen.” For something to be collagen, two things must be true. The first is a pattern in the protein itself: collagen is made of amino acids, and along its rope-like stretch, every third amino acid is glycine, repeating over and over [5,6]. In the collagens that build tendon, skin, and bone, that rhythm runs unbroken for more than three hundred repeats [5]. It’s what lets three chains wind around each other into a rope, and it’s the closest thing collagen has to a signature.

The second requirement is that the sequence belongs to an animal. Collagen is an animal protein. Plants don’t have the gene for it. Plants do not have collagen.

What Is “Vegan Collagen”?

Simply put, marketing. “Vegan collagen” gets used for two genuinely different things.

The first is blends of plant amino acids. These are reasonable raw material for a supplement, but not collagen, any more than flour is bread. What makes collagen interesting comes from short peptides with a very specific order of amino acids, sequences that sit quietly inside the full protein until something cuts them free [7]. A loose mix of amino acids has no order to it; therefore, there’s nothing in it to cut free.

The second is genuinely collagen, made through biotech. Take the human collagen sequence, sourced computationally, and brew it in a fermentation tank, the same basic approach used to make insulin since the 1980s, and what comes out is collagen. It checks both boxes: (1) glycine repeated sequence and (2) animal sequence. That is where the term biomimetic comes from: it replicates the animal sequence exactly, with no animal involved in producing it. Nothing is farmed, slaughtered, or extracted. The sequence is taken from a database and given to a microbe, which does the work, allowing it also to be truly vegan.

So the useful question about a “vegan collagen” claim isn’t whether such a thing can exist. It’s which of the two you’re holding, a blend of amino acids that isn’t collagen, or a biomimetic collagen made with biotech.

There’s one more difference worth knowing, and it has nothing to do with vegan or not. Animal-derived collagen is never just one type. Extraction pulls out whatever’s abundant and easy to get from a given tissue; in skin, that’s mostly Type 1 with some Type 3 mixed in, plus trace amounts of whatever else came along for the ride. It’s less a single ingredient than a soup, and the ratio isn’t something a manufacturer controls so much as inherits from the source material.

Biotech collagen doesn’t have that problem, because it isn’t extracted from anything. It’s produced from a single defined sequence, which means it can be made as one pure type, at a defined purity, every time. That’s not a minor technical detail; it’s the difference between a product built on a known, consistent ingredient and one built on whatever a particular animal’s tissue happened to contain. Its purity, consistency, and potency derived from a single type of collagen can also impact its efficacy, enabling biotech-derived collagen to be used at a fraction of the usage level of animal-derived collagen.

The biotech platforms producing collagen with biodesign and precision fermentation are able to transcend the collagen category from a byproduct to an intentionally crafted active ingredient that delivers on naturality, innovation, and most importantly, efficacy. These platforms unlock the full potential of collagen and other proteins, like elastin, that are otherwise far too rare to extract or purely inaccessible, including some of the more interesting signaling types buried in that list of 28, like type 21.

References
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1. Ricard-Blum S. The Collagen Family. Cold Spring Harbor Perspectives in Biology 2011; 3(1):a004978. https://doi.org/10.1101/cshperspect.a004978
2. Sophia Fox AJ, Bedi A, Rodeo SA. The Basic Science of Articular Cartilage: Structure, Composition, and Function. Sports Health 2009; 1(6):461–468. https://doi.org/10.1177/1941738109350438
3. Myllyharju J, Kivirikko KI. Collagens, modifying enzymes and their mutations in humans, flies and worms. Trends in Genetics 2004; 20(1):33–43. https://doi.org/10.1016/j.tig.2003.11.004
4. The UniProt Consortium. UniProt: the Universal Protein Knowledgebase in 2025. Nucleic Acids Research 2025; 53(D1):D609–D617. https://doi.org/10.1093/nar/gkae1010
5. Hulmes DJS. Collagen Diversity, Synthesis and Assembly. In: Collagen: Structure and Mechanics. Springer, 2008:15–47. https://doi.org/10.1007/978-0-387-73906-9_2
6. Shoulders MD, Raines RT. Collagen Structure and Stability. Annual Review of Biochemistry 2009; 78:929–958. https://doi.org/10.1146/annurev.biochem.77.032207.120833
7. Venkatesan J, Anil S, Kim S-K, Shim MS. Marine Fish Proteins and Peptides for Cosmeceuticals: A Review. Marine Drugs 2017; 15(5):143. https://doi.org/10.3390/md15050143
8. Leitinger B, Hohenester E. Mammalian collagen receptors. Matrix Biology 2007; 26(3):146–155. https://doi.org/10.1016/j.matbio.2006.10.007
9. Ricard-Blum S, Ruggiero F. The collagen superfamily: from the extracellular matrix to the cell membrane. Pathologie Biologie 2005; 53(8):430–442. https://doi.org/10.1016/j.patbio.2004.12.024