Glycine is known to boost mood too, since it stimulates the production of serotonin—the hormone that makes you feel good.  Glycine is also one of the three amino acids that make creatine, which is key to build muscles and provides them with an energy boost when doing intense workouts or weight lifting.  If better sleep, good mood and beautiful muscles isn’t enough, Glycine is also the main amino acid in collagen — which is responsible for strength, structure and support of your skin, muscles, bones and connective tissues.