L-Glutamine is a non-essential amino acid that supplies energy to the brain and is thought to have a positive effect on increased concentration. Athletes on high-protein diets will appreciate the fact that L-Glutamine transports ammonia - the metabolic by-product of protein breakdown - to the liver where it is converted into urea and excreted by the kidneys. L-Glutamine can also convert into alanine, an amino acid that the liver converts into glucose, supplying additional fuel to muscles.