Collagen peptides are enzymatically hydrolyzed animal collagen (bovine, marine, or chicken) broken to short di- and tripeptides for absorption.
Mechanism — Provides high-glycine, proline, and hydroxyproline amino acid pool. Specific dipeptides (hydroxyprolyl-glycine, prolyl-hydroxyproline) appear to signal fibroblast collagen synthesis directly. Skin elasticity and tendon outcomes have RCT support.
Use case — Skin, hair, nails, joint and tendon support. 10-20 g/day, ideally with vitamin C cofactor. Consider 15 g 30-60 min before tendon-loading training for tendon adaptation.
Caveats — Generic 'collagen for skin' marketing is overblown; the data is real but modest. Doesn't replace whole-food protein for muscle protein synthesis.