Glutamine is the most abundant amino acid in your body. It helps with cell-volumization, digestion, and immune system support. It is free amino acid in muscle tissue, and it plays a principal role in protein metabolism, and anti-catabolism. Catabolism is the breaking down of protein in your muscles. Glutamine can also be converted to gylcogen to use for energy rather than breaking down protein in the muscle during strenuous exercise. Glutamine can be extremely useful for anyone trying to lose fat and keep as much muscle as they can. This is one of the most important supplements I use.