Collagen is a connective tissue and is the cement that holds everything together-the primary mortar between the bricks of all of our smooth muscle tissues such as blood vessels, digestive tract, heart, gallbladder, kidneys and bladder to mention just a few. Collagen, along with Elastin, is a key structural component of bones, cartilage, tendons, the skin, lung tissue and blood vessels. Collagen provides structure and firmness to body tissues, Elastin provides flexibility to those same tissues. If you don't consume enough calories and proper amounts of Amino Acids from the protein in your diet, you can go into negative nitrogen balance. This means your body can become cannibalistic and actually break down the protein in your own muscle tissues if you restrict calories too much , especially when you limit your intake of protein too drastically.
Protein is the body's main source of nitrogen.
It is critical to maintain positive nitrogen balance, especially during weight loss and body building. Lean body mass is where most of our energy is consumed and that energy is measured in units called calories. Calories are not used up in fat tissue. So, the less lean body tissue you have, the less calories you can consume. We get weaker as this happens and our ability to burn calories decreases.