L-Glutamine is used by the body as fuel for the brain and is used up in larger quantities during periods of ill health. It is also involved in the growth and regrowth of the tissue lining of the gut and is a popular supplement for individuals with leaky gut syndrome. Amino Acids are essential to health. Most form the small structural components of protein and are required for the synthesis of protein within the body. The primary function of most Amino Acids is to furnish the essential material for duplication of the genetic code, for cell division, and for the formation of muscles and connective tissue.