Collagen peptides are made from animal connective tissues, primarily the hides, bones, and cartilage of cows, the skin and scales of fish, and the cartilage of poultry like chicken and turkey. These raw tissues undergo a multi-step process that breaks the large collagen protein down into small, easily absorbed fragments. The source animal and specific tissue determine which type of collagen you end up with, which matters depending on your goals.
The Raw Materials Behind Each Source
Bovine collagen, the most common type on the market, comes from cowhides and bones. It contains both type I collagen (the kind most abundant in human skin, tendons, and bones) and type III collagen, which provides strength and flexibility to soft tissues like blood vessels and organs. This broader mix makes bovine collagen a popular choice for people looking for general support across skin, joints, and gut health.
Marine collagen comes from the skin, scales, and bones of fish. It’s rich in type I collagen specifically, making it a frequent pick for skin, hair, and nail goals. Marine collagen may also be absorbed more efficiently than bovine, likely because the peptides from fish tend to be slightly smaller.
Chicken collagen is distinct from both. The cartilage from chicken sternums (breastbones) is a rich source of type II collagen, the dominant collagen in cartilage tissue. Type II collagen is the one linked to joint health, helping to reduce stiffness and improve mobility. Turkey by-products, including heads and cartilage, are also processed into collagen peptides, turning low-value poultry waste into a functional ingredient.
How Collagen Becomes Peptides
Native collagen, straight from the animal, is an enormous molecule with a molecular weight around 300,000 Daltons. At that size, your body can’t absorb it. The manufacturing process breaks it down in stages to make it usable.
First, the raw tissues are cleaned, and the collagen is extracted. For most products, this involves boiling bones, cartilage, and skin for several hours. If you stop the process here and let the liquid cool and set, you get gelatin, the wobbly substance used in cooking. Gelatin is partially broken-down collagen, but it’s still too large for efficient absorption as a supplement.
To create collagen peptides, manufacturers take the process further using enzymatic hydrolysis. Specific enzymes are added to chop the collagen chains into much smaller pieces. Different enzymes can be used alone or in combination, and the choice affects how small the final peptides are. Research on turkey collagen, for example, found that using a cocktail of three enzymes together produced the greatest amount of low-molecular-weight peptides. The final product typically contains molecules between 2,000 and 6,000 Daltons, though the range can span from about 1,000 to 8,000 Daltons depending on the manufacturer’s process.
This is why supplement labels say “hydrolyzed collagen” or “collagen peptides.” Both terms describe the same thing: collagen that has been enzymatically broken into fragments small enough to dissolve in water and pass through your gut lining.
What’s Actually in the Peptides
Collagen has a distinctive amino acid profile that sets it apart from other proteins. In 100 grams of hydrolyzed collagen peptides, roughly 22 grams are glycine, about 13 grams are proline, and nearly 12 grams are hydroxyproline. That trio dominates the composition and is largely responsible for collagen’s structural role in the body. Hydroxyproline in particular is almost exclusive to collagen, which is why blood levels of hydroxyproline are sometimes used to track whether collagen supplements are actually being absorbed.
What collagen lacks is also notable. It’s low in several essential amino acids, which means it’s not a complete protein and shouldn’t be treated as a replacement for other protein sources in your diet.
How Your Body Absorbs Them
Your body can’t absorb collagen in its whole form, even from food. Collagen proteins must first be broken into smaller peptides or individual amino acids. Collagen supplements skip most of that digestive work because they’ve already been hydrolyzed into fragments just two or three amino acids long. These tiny peptides are absorbed through the gastrointestinal tract and enter the bloodstream, where they can travel to skin, joints, and other tissues.
This is the key advantage of collagen peptides over eating collagen-rich foods like bone broth. The pre-broken peptides offer higher bioavailability, meaning a greater percentage of what you swallow actually reaches your bloodstream in a usable form.
What About Vegan Collagen?
True collagen is an animal protein, so there’s no plant that naturally contains it. Products marketed as “vegan collagen” are typically collagen biomimetics: blends of plant extracts and fermented amino acids designed to stimulate your body’s own collagen production rather than supply collagen directly. These formulas often include compounds from plants like centella asiatica and ginseng that support the body’s natural type I collagen synthesis. One double-blind, placebo-controlled study found that an oral vegan collagen biomimetic did produce measurable benefits for skin, but the mechanism is fundamentally different from taking animal-derived collagen peptides.
If you see a supplement labeled “vegan collagen,” read the ingredients carefully. You’re getting collagen-boosting plant compounds, not hydrolyzed collagen peptides.
Purity and Quality Vary
Collagen supplements are not regulated with the same rigor as pharmaceuticals, which means ingredient quality and contaminant levels can vary between brands. Because collagen is extracted from animal tissues, there’s potential for heavy metals like lead, cadmium, mercury, and arsenic to be present. Reputable manufacturers test for these contaminants: a typical lab report might show lead under 0.01 parts per million and mercury below 0.02 ppm, well within safe thresholds. But not every brand conducts or publishes this testing.
Third-party certifications from organizations like NSF International or USP can help you identify products that have been independently tested. If a brand doesn’t provide a certificate of analysis or third-party verification, that’s worth noting when you’re comparing options.