Collagen Peptides

Collagen is the most abundant protein in the body, forming the structural framework of skin, tendon, ligament, cartilage and bone. It is characterised by an unusual amino acid profile dominated by glycine, proline and hydroxyproline, arranged in a triple helix.

Intact collagen is too large to absorb, so supplements use hydrolysed collagen, enzymatically cleaved into peptides of roughly 2,000 to 5,000 daltons. Sources include bovine hide, porcine skin, marine fish skin and scales, and eggshell membrane. Marine collagen is predominantly type I and is often preferred for skin applications; bovine supplies types I and III; type II, relevant to cartilage, is usually sourced from chicken sternum.

An important distinction exists between hydrolysed collagen peptides and undenatured type II collagen. The latter is used at very small doses, around 40 mg, and works through an entirely different immune-mediated mechanism. The two are not interchangeable despite both being called collagen.

The long-standing objection to collagen supplementation is that it is digested into amino acids like any protein, so eating collagen should not preferentially build collagen. That objection is partly right and partly outdated.

Certain collagen-derived dipeptides and tripeptides, notably prolyl-hydroxyproline, survive digestion intact and appear in the bloodstream. These peptides seem to act as signalling molecules, stimulating fibroblast activity and collagen synthesis rather than serving purely as building blocks. That signalling role, rather than raw amino acid supply, is the more credible mechanism.

Collagen synthesis is also vitamin C dependent, since the enzymes that hydroxylate proline and lysine require it as a cofactor. This is why vitamin C co-ingestion is a genuine formulation consideration rather than a marketing addition, and why some tendon protocols specify it explicitly.

Skin outcomes have the strongest support. Multiple randomised controlled trials and meta-analyses report improvements in skin elasticity and hydration over 8 to 12 weeks. Effect sizes are modest and the literature carries significant industry funding, but the direction of findings is reasonably consistent.

Joint discomfort research, particularly in athletes and in people with activity-related knee pain, has generally reported symptomatic improvement. Work on tendon and ligament properties is a smaller but interesting area, with some evidence that peptides taken with vitamin C around an hour before loading exercise support collagen synthesis in connective tissue.

Where the evidence does not support the marketing is muscle protein synthesis. Collagen is a poor-quality protein by amino acid scoring, low in leucine and lacking tryptophan, and should not be counted toward a daily protein target for muscle building purposes. It is a targeted connective tissue supplement, not a protein supplement.

Collagen peptides have an excellent safety record. Adverse effects are uncommon and mild, most often a feeling of fullness, mild digestive upset or an unpleasant aftertaste, particularly with marine collagen.

The material considerations are allergen and sourcing related rather than pharmacological. Marine collagen is a fish product and must carry allergen declaration under food information requirements. Bovine and porcine sources raise dietary suitability questions for some customers, and none of these products are suitable for vegetarians or vegans regardless of how they are marketed.

Sourcing traceability matters for bovine collagen. Confirm supplier documentation covering origin and processing.