Collagen is the most abundant protein in the body and is the main component of all connective tissues. It is the tough, fibrous protein in hair, nails, tendons, ligaments, and skin. Collagen provides the infrastructure of the musculoskeletal system, which is essential for mobility. As we age, our body begins producing less collagen, which is one reason why skin starts to sag and joints become achy. Numerous studies show that collagen strengthens bones, joints, and ligaments, in addition to helping reduce joint pain and stiffness.