Collagen is the most abundant protein in the human body, making up about 25-35% of the entire body’s protein content.  At this time, researchers have identified 28 types of collagen.  Types I and V are those found in skin.  Collagen is a structural protein found in the extracellular space.  In the skin, collagen imparts strength and elasticity.  As we age, our body’s collagen production begins to slow, causing wrinkles, sagging skin, etc.