Scientifically speaking, glutamine is one of the 20 amino acids formed by the human body. Glutamine is considered a non-essential amino acid because it can be derived from glutamic acid, another member of the amino acid family. Both glutamine and glutamic acid can be found in protein-rich foods such as beans, red meat, nuts and fish. The body uses glutamine to improve mental function, control blood sugar levels and maintain muscle mass, among other applications.

As a supplement, glutamine is seen as both a 'brain food' and a muscle mass enhancer for body builders. Physicians have been known to use glutamine for the treatment of alcoholism, mild depression and muscle-wasting conditions such as Huntington's disease. Glutamine is actually the most common free-form amino acid found floating in muscle tissues. During times of stress, the body may draw glutamine away from the muscles in order to bolster the immune system or prevent blood sugar reactions. This is why many bodybuilders and other proponents of supplements often add daily doses of glutamine to maintain good muscle health.

The average diet provides anywhere from 5 to 8 grams of glutamine a day. It would not be unusual for bodybuilders in training to boost this level to 10 grams or more with glutamine supplements. Others who need to control blood sugar levels may also benefit from additional glutamine. Some non-scientific studies suggest that glutamine may also help improve mental function, because the body naturally uses glutamine to transport nitrogen to the brain and nervous system.

The human body does require a daily intake of glutamine, so the use of supplements is not generally seen as harmful or unnecessary. Higher doses of glutamine may cause unpleasant side effects such as diarrhea, but most healthy bodies can safely assimilate the excess amino acid. Supplemental glutamine simply remains suspended in muscle tissue unless drawn away for other uses by the body. Some people also discover that elevated glutamine levels reduce their desire for sweets or between-meal snacks.