Collagen is a complex structural protein that is present in our muscles and connective tissues including tendons and ligaments, as well as our hair, skin and nails. Collagen makes up 30% of the body’s protein and contains 19 different amino acids, which are vital building blocks for tissues. There are at least 28 different types of collagen. The most common are types 1 to 5, with type 1 the most plentiful, accounting for 90% of total collagen in our bodies.