Collagen is one of the most abundant proteins in the human body and the amino acids that make it up are essential building blocks in supporting the integrity and structure of our skin, bones, tendons, ligaments, muscles, blood vessels, and teeth as well as the entire gastrointestinal tract lining. As we age, our body gradually produces less. It is pretty different for everyone, but genetics, stress level, diet, smoking, age, and sun exposure may all influence how much we are producing.