Collagen is the most abundant protein in the body. Initially, the body naturally produces its own supply of collagen which it relies on to maintain healthy skin, hair, nails, joints, muscles, bones, and digestive lining.
Long ago the human diet consisted of collagen-rich staples such as organ meats, boiled down bones, cartilage, tendons and all the "grisly" pieces of the animal.
While extremely rich in collagen, eating a daily diet like this isn't very convenient or appetizing in the busy modern world.
As a result, today's modern diet is missing the rich source of dietary collagen that helps replenish the body's natural collagen levels.