The most abundant "free" amino acid in the body. It is found in higher concentration than other amino acids in vital tissues including the brain, intestinal mucosa cells, immune cells and skeletal and smooth muscle. In muscle, the concentration of free glutamine appears to influence whether muscle will be broken down (catabolism-low glutamine content) or built up (anabolism-high glutamine content). Glutamine is known as a nitrogen shuttle, a substance that picks up and drops off nitrogen around the body. Nitrogen is an essential component of DNA, the genetic material of life and muscle building. Glutamine is a prominent contributor to the functional integrity of the intestines and serves as an energy source for these high activity cells. In the cells of the immune system, glutamine is pivotal in their response to "foreign" challenges, by serving both as metabolic fuel and as precursor to RNA & DNA. Glutamine is the dominant amino acid in cerebrospinal fluid and readily enters the brain where it can serve as a precursor to neurotransmitters. Glutamine is readily absorbed from the intestinal tract and has a mildly sweet taste.