How Fast Tendons Turn Over and the Forms of Dietary Collagen

Keith opens with his funding disclosures and the aims of the session, then challenges the idea that connective tissue is inert. Data from Luc van Loon's lab, taken during total knee replacement, show the ACL turning over almost 70% faster than muscle and the patellar tendon 40 to 50% faster, while the rarely loaded PCL turns over slowly and cartilage matches muscle. Tendons and ligaments may grow like trees, adding outer rings while the core changes little. An MRI study of women soccer players found a 15% increase in ACL size over an 8-month season, which implies a similar loss during the off-season. Work on engineered human ligaments showed that vitamin C, proline and glycine made them much stronger, which led to dietary collagen. Keith explains that collagen comes only from animals, that gelatin is heat-denatured collagen and hydrolyzed collagen is gelatin broken into smaller pieces, and that vitamin C is a cofactor for prolyl hydroxylase, without which collagen cannot leave the cell.