Collagen constitutes approximately 30 percent of total body protein and is the primary structural protein in connective tissue, skin, bone, cartilage, tendons, and blood vessel walls. After 40, collagen synthesis declines at a rate of approximately 1 to 2 percent per year. This decline contributes to joint stiffness, reduced skin elasticity, impaired tendon strength, and reduced gut barrier integrity. Dietary strategies that support collagen synthesis and provide collagen precursors can meaningfully slow this decline.
The Evidence for Collagen Peptides
Hydrolysed collagen peptides are absorbed as dipeptides and tripeptides including hydroxyproline-glycine and hydroxyproline-proline, which are detectable in blood after oral ingestion. Research has shown that these peptides accumulate in cartilage tissue and stimulate chondrocytes to produce more collagen. A systematic review and meta-analysis of 15 randomised controlled trials found that collagen peptide supplementation significantly reduced joint pain and improved joint function in adults with osteoarthritis and exercise-related joint pain.
Food Sources of Collagen Peptides and Glycine
- Bone broth: simmering bones for 8 to 24 hours extracts collagen, glycine, proline, and hydroxyproline; use as a base for soups and stews or drink as a warm broth
- Skin-on chicken and fish: the skin is rich in collagen and provides significantly more glycine per serving than skinless versions
- Gelatine: the cooked form of collagen; use in making panna cotta, jellies, and slow-cooked meat dishes
- Slow-cooked meat cuts: shoulder, shin, and oxtail release collagen during long cooking; braising and stewing are the appropriate methods
- Combine collagen food sources with vitamin C-rich foods to support the hydroxylation step in collagen synthesis