What is collagen? Role, types, diet and supplements

Reading time: 8 minutes

Collagen is everywhere in our body, and in more and more food supplements. But what does it do, what happens to it when you swallow it, and how do you choose a supplement? We've gathered the essentials here, based on the scientific and regulatory sources listed at the end of the article.

Collagen, the body's structural protein

Collagen is one of the most abundant proteins in the human body. It forms very strong fibres that give structure and strength to skin, tendons, ligaments, cartilage and bones. It works a bit like a framework: it doesn't “do”, it “holds”.

What is it made of?

Like all proteins, collagen is a chain of amino acids. Its chain follows a pattern repeated hundreds of times: glycine – X – Y, where X is often proline and Y hydroxyproline. Glycine alone makes up about a third of collagen's amino acids; proline and hydroxyproline make up roughly another fifth (Shoulders and Raines, 2009).

Three of these chains wind around each other to form a very tight triple helix. This structure is what makes it so strong.

Hydroxyproline is almost unique to collagen: very little of it is found in other proteins. To make it, the body needs vitamin C, which contributes to normal collagen formation for the normal function of skin, bones and cartilage.

On the other hand, collagen contains no tryptophan, one of the 9 essential amino acids. So it is not a complete protein, and it doesn't replace the other proteins in your diet (see our article Mixing whey and collagen: a good idea?).

The main types of collagen

Researchers have identified 28 types of collagen (Ricard-Blum, 2011). Not all of them form fibres: some form networks, others link fibres together. Five are particularly well known (Gelse et al., 2003):

Supplements mainly provide type I, often with type III. Our Liquid Marine Collagen contains types I and III.

What affects collagen

Our collagen production gradually declines with age. Some factors also speed up its breakdown:

• Smoking.
• UV rays: prolonged sun exposure damages the collagen fibres in the skin (see The sun destroys your collagen).
• Too much sugar: sugars attach to proteins (this is glycation) and stiffen the fibres.

Collagen and diet

Collagen is found in animal foods rich in connective tissue: bone broths, fish and poultry skin, gelatine.

Vitamin C plays a key role, recognised by European regulations: it contributes to normal collagen formation for skin, cartilage, bones and blood vessels (EU Regulation No 432/2012). It is found in citrus fruit, kiwi, peppers, broccoli and papaya.

What happens to collagen when you swallow it?

One objection comes up often: “collagen is destroyed by digestion”. That's partly true: like any protein, it is broken down into amino acids. But not only that. One study found small intact collagen fragments in the blood, including a dipeptide called Pro-Hyp, one to two hours after taking hydrolysed collagen (Iwai et al., 2005). Another confirmed the presence of Pro-Hyp and a second fragment, Hyp-Gly (Shigemura et al., 2011). So part of the collagen is absorbed as peptides.

Hydrolysed, peptides, daltons: what does it all mean?

• Native collagen: the large triple-helix molecule, as it exists in the body. Too big to be absorbed as is.
• Gelatine: heated collagen whose helix has come apart. It forms a gel as it cools.
• Hydrolysed collagen (or collagen peptides): collagen cut by enzymes into small pieces, the peptides. It dissolves in cold water and doesn't form a gel (León-López et al., 2019).
• The dalton (Da) is the unit used to measure the size of these pieces: the lower the number, the smaller the peptide. The peptides in our Liquid Marine Collagen are under 2,000 daltons, a size that is essential for good absorption through the gut wall.

Collagen supplements

Most supplements contain hydrolysed collagen: it has been cut into peptides, which are easier to digest and dissolve. They come in liquid, powder or capsule form (we compare these three formats in Liquid, powder or capsule collagen: what are the differences?). To compare them, look at:

• the amount of collagen per daily serving, not per bottle or tub;
• its origin (marine, for example);
• whether it contains vitamin C;
• the full composition, including sugars and flavourings;
• quality and analysis certificates.

For a detailed comparison of marine collagens, read our guide: Which marine collagen should you choose?

How we chose our collagens

Vitamoon sells collagen supplements: we'd rather say so clearly. Here are the choices we made, and why:

• A hydrolysed collagen, so it dissolves and digests easily.
• A stated daily dose (10,000 mg for Liquid Marine Collagen), so you can compare at a glance.
• PEPTAN® collagen peptides for our two drinks, the Choco Latte and the Matcha Latte.
• Vitamin C in Liquid Marine Collagen and Collagen Choco Latte, for its recognised role in collagen formation.
• Made in Europe, with a certificate of analysis (COA) checked for every batch.

Frequently asked questions

Is there a vegan collagen?

No. Collagen is always of animal origin. So-called “vegan” products provide nutrients, such as vitamin C, that contribute to the body's collagen formation, but no collagen.

What is marine collagen?

It is collagen extracted from fish skin or scales, mainly type I. It is not suitable for people allergic to fish. To compare it with bovine collagen, read Marine or bovine collagen: which should you choose?

How long should you take it?

There is no official duration. If you do a course, take it every day over several weeks: consistency is what counts.

Can it be taken with other supplements?

Generally yes, for example with whey. If you are pregnant, breastfeeding or on medical treatment, ask your doctor or pharmacist for advice.

Our collagens

• Liquid Marine Collagen: 10,000 mg of hydrolysed marine collagen (types I and III), with hyaluronic acid, biotin and vitamin C. One 25 ml shot a day.
• Collagen Choco Latte: 8,500 mg of PEPTAN® collagen peptides, cocoa, organic coconut milk and vitamin C.
• Collagen Matcha Latte: 8,500 mg of PEPTAN® collagen peptides and organic matcha green tea.

In summary

• Collagen gives structure to skin, tendons, cartilage and bones.
• Its production declines with age; smoking, UV rays and too much sugar damage it.
• Part of hydrolysed collagen is absorbed as peptides.
• Vitamin C contributes to normal collagen formation.
• In a supplement, look at the daily dose, the origin and whether it contains vitamin C.

Sources

• Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods (vitamin C and collagen formation).
• Ricard-Blum S., “The Collagen Family”, Cold Spring Harbor Perspectives in Biology, 2011.
• Iwai K. et al., “Identification of food-derived collagen peptides in human blood after oral ingestion of gelatin hydrolysates”, Journal of Agricultural and Food Chemistry, 2005.
• Shoulders M.D., Raines R.T., “Collagen structure and stability”, Annual Review of Biochemistry, 78, 929-958, 2009.
• Gelse K., Pöschl E., Aigner T., “Collagens: structure, function, and biosynthesis”, Advanced Drug Delivery Reviews, 55(12), 1531-1546, 2003.
• Shigemura Y. et al., “Identification of a novel food-derived collagen peptide, hydroxyprolyl-glycine, in human peripheral blood by pre-column derivatisation with phenyl isothiocyanate”, Food Chemistry, 129(3), 1019-1024, 2011.
• León-López A. et al., “Hydrolyzed collagen: sources and applications”, Molecules, 24(22), 4031, 2019.

About the author

Nicolas is the owner of Vitamoon, a brand of liquid and powder food supplements made in Europe, which he took over in 2025 and runs with his wife. He writes the blog articles based on the scientific and regulatory sources listed above.