What Is Collagen? Collagen is the most abundant protein in the body and is a major structural component of skin, hair, nails, joints, bones, muscles, and connective tissue. As we age, natural collagen production gradually declines, which is why collagen supplements have become increasingly popular for supporting skin health, joints, recovery, and healthy aging. Collagen supplements are typically made from hydrolyzed collagen peptides, which are broken down into smaller amino