Collagen holds your body together, but swallowing it won't smooth your skin
Collagen is the most plentiful protein in mammals, a quarter to a third of all the protein you carry. Supplement makers promise that eating or rubbing it in will firm up skin. Your gut simply breaks it into amino acids, and creams cannot get it through the skin at all.
The name comes from the Greek word for glue, and English adopted it in 1843. Collagen is the main structural protein of connective tissue, built as three chains wound into a tight triple helix. Mineralise it heavily and you get rigid bone; leave it unmineralised and you get supple tendon; grade it between the two and you have cartilage. It also shapes corneas, blood vessels, spinal discs and dentin, and fibroblasts are the cells that make most of it.
At least 28 human types have been described, coded by about 45 genes that carry the COL prefix, though types I and III account for more than 90 percent. Type I dominates skin, tendon and the organic part of bone; type II is the collagen of cartilage. Its chemistry is unusual, dense in glycine, proline and a modified form called hydroxyproline. Adding those hydroxyl groups requires enzymes that depend on vitamin C, consuming one ascorbate molecule per reaction. Go without the vitamin for long and the helix loosens, which is what happens in scurvy.
Medicine puts collagen to real use. Scaffolds of it, as sponges, sheets, gels or fibres, give bone and tendon cells a framework to colonise. Collagen from cows, horses, pigs or people goes into artificial skin for severe burns, and as a dressing it resists bacteria and lets new tissue grow across a wound. Dentists pack absorbable collagen sponges into sockets after extractions to encourage clotting.
Commercially, food leads: in 2024 about 55 percent of the American collagen market went into foods such as sausage casings, thickeners and ice cream, much of it as gelatin. The beauty claims are weaker. As of 2025, no clinical evidence showed that oral supplements or collagen creams improve wrinkles or ageing skin.
Source: Collagen
