Glutamine

# Overview
Glutamine (abbreviated as Gln or Q; Glx or Z represents either glutamate or glutamic acid) is one of the 20 amino acids encoded by the standard genetic code. Its side chain is an amide formed by replacing the side-chain hydroxyl of glutamic acid with an amine functional group. It can therefore be considered the amide of the acidic amino acid glutamate. Its codons are CAA and CAG.

# Nutrition

## Occurrences in nature
Glutamine is the most abundant naturally occurring, non-essential amino acid in the human body. In the body it is found circulating in the blood as well as stored in the skeletal muscles. It becomes conditionally essential (requiring intake from food or supplements) in states of illness or injury.

### Dietary sources
Food sources of glutamine include:
- Animal sources: meat, fish, eggs, milk, yogurt, ricotta cheese, cottage cheese,
- Plant sources: beans, spinach, parsley, cabbage. Small amounts of free L-glutamine are found in vegetable juices and fermented foods, such as miso 

## Functions
- A substrate for DNA synthesis.
- Major role in protein synthesis.
- Primary source of fuel for enterocytes (cells lining the inside of the small intestine).
- Precursor for rapidly dividing immune cells, thus aiding in immune function.
- Regulation of acid-base balance in the kidney.
- Alternative source of fuel for the brain and helps to block cortisol-induced protein catabolism.
- As a form of fixed nitogen by heterocysts, exchanged for photosynthate from undifferentiated cyanobacterial cells.
Polar (uncharged)

## Use
In catabolic states of injury and illness, GLN becomes conditionally-essential (requiring intake from food or supplements). Glutamine has been studied extensively over the past 10-15 years and has been shown to be useful in treatment of serious illnesses, injury, trauma, burns, cancer and its treatment related side-effects as well as in wound healing for postoperative patients (citation pending). That is why it is now also classified as a "nutraceutical". Glutamine is also marketed as a  supplement used for muscle growth in weightlifting, bodybuilding, endurance and other sports.

## Aiding gastrointestinal function
There have been several recent studies into the effects of glutamine and what properties it possesses, and, there is now a significant body of evidence that links glutamine-enriched diets with intestinal effects; aiding maintenance of gut barrier function, intestinal cell proliferation and differentiation, as well as generally reducing septic morbidity and the symptoms of Irritable Bowel Syndrome. The reason for such "cleansing" properties is thought to stem from the fact that the intestinal extraction rate of glutamine is higher
than that for other amino acids, and is therefore thought to be the most viable option when attempting to alleviate conditions relating to the gastrointestinal tract. 
These conditions were discovered after comparing plasma concentration within the gut between glutamine-enriched and non glutamine-enriched diets. However, even though glutamine is thought to have "cleansing" properties and effects, it is unknown to what extent glutamine has clinical benefits, due to the varied concentrations of glutamine in varieties of food. 

## Aiding recovery after surgery
It is also known that glutamine has various effects in reducing healing time after operations.  Hospital-stay times after abdominal surgery can be reduced by providing parenteral nutrition regimes containing high amounts of glutamine to patients. Clinical trials have revealed that patients on supplementation regimes containing glutamine have improved nitrogen balances, generation of cysteinyl-leukotrienes from polymorphonuclear neutrophil granulocytes and improved lymphocyte recovery and intestinal permeability (in postoperative patients) - in comparison to those who had no glutamine within their dietary regime; all without any side-effects.