What Is Collagen?

Collagen is the most abundant protein in the human body, making up around 30% of total protein and forming the main structural component of connective tissue. You can think of it as the body's scaffolding: it gives skin its firmness, bones their framework, tendons and ligaments their strength, and cartilage its cushioning. The word comes from the Greek for glue, which reflects its job of holding tissues together. Collagen is produced continuously by specialised cells, most notably fibroblasts in the skin, using amino acids from the diet together with vitamin C. The authorised position here is precise: vitamin C contributes to normal collagen formation for the normal function of skin, bones, cartilage, gums, teeth and blood vessels.

Collagen has a distinctive triple-helix structure - three protein chains wound tightly around one another like a molecular rope. This shape is what gives collagen its tensile strength. It is built from a repeating amino acid pattern dominated by glycine, proline and hydroxyproline. Glycine, the smallest amino acid, appears at roughly every third position, allowing the three chains to pack closely together. Hydroxyproline is comparatively rare in other proteins, which makes it a useful marker of collagen specifically. These helices assemble into fibrils and then into larger fibres, creating the durable networks found throughout connective tissue.

Although at least 28 collagen types have been identified, three account for the majority in the body. Type I is the most common, found in skin, bone, tendon, ligament and the cornea, and is the primary type targeted by skin-focused products. Type II is the main collagen of articular cartilage, making it the most relevant where joint structure is concerned. Type III is widely distributed alongside Type I in skin, blood vessels and internal organs, and is especially important in tissues that need elasticity. Supplement sources reflect these differences: marine collagen is mostly Type I, bovine supplies Types I and III, and chicken-derived collagen is a notable source of Type II.

In the skin, collagen forms the dermal matrix that keeps the surface firm and supple, working alongside elastin and hyaluronic acid. In bone, it provides the flexible protein framework on which minerals are deposited, balancing rigidity with resistance to fracture. In tendons and ligaments, densely packed collagen fibres transmit force between muscle and bone. In cartilage, it absorbs and distributes load across joints. Collagen also lines blood vessels and supports the gut wall. Because it is so widespread, collagen is fundamental to how the body holds its shape and withstands everyday mechanical stress.

The body's natural collagen production gradually slows from around the mid-twenties, and existing fibres become more fragmented with age. This is a normal biological process influenced by genetics, diet, sun exposure, smoking and overall health rather than something a supplement claims to reverse. As production declines, connective tissue can lose some of its firmness and resilience over the years. This natural change is one reason interest in dietary collagen and supplements tends to grow from the thirties onwards, typically as part of a broader routine that supports general wellbeing alongside a balanced diet.

The body synthesises collagen from amino acids supplied by protein in the diet, with vitamin C as an essential cofactor. Glycine and proline, two of collagen's building blocks, are found in a range of protein foods, while foods such as bone broth, skin-on fish and slow-cooked meats contain collagen directly. Supplements provide hydrolysed collagen - collagen broken into smaller, easily absorbed peptides - as a convenient standardised source. Collagen from supplements is animal-derived, so it is not suitable for vegans. Food supplements are not medicines; if you have a health concern, speak to a GP or pharmacist.