L-carnitine is an amino acid that helps your body metabolize fat. Without adequate amounts of L-carnitine, your body would not be able to utilize fat as energy. Glutamine is the most abundant amino acid in your body. Glutamine is especially important for building proteins. Glutamine also helps your body remove excess amounts of ammonia, a waste product produced by the breakdown of protein. Glutamine also allows your immune system to function correctly and plays an important role in the digestion process and proper brain function.