In order to understand how a "non-essential amino acid" can attract so much attention it is necessary to understand where the term "non-essential" comes from. An amino acid is only considered essential if it is not possible for the body to make the particular amino acid when there is adequate supply of other "essential" amino acids. Since it is possible to make glutamine from many different amino acids, including glutamic acid, valine and isoleucine, it is not considered essential however the fact that the body has a number of ways to produce glutamine may serve to illustrate its importance.

Glutamine is also a precursor for many other amino acids; an important fuel for the immune system, the brain and gut mucosal cells, and it is at the heart of a mechanism controlling acid:base balance. It may also be a direct regulator of protein synthesis and regulation, thus glutamine is at the heart of a metabolic cross roads and its adequate supply is thus crucial for optimal functioning of the body.

Glutamine has been used routinely in hospitals for the treatment of burn and other trauma patients where it has been shown to help improve immune function. Recently research has focused on the parallels between the trauma of "hospitalisation" and the trauma of exercise stress. Under these conditions the body's requirement for glutamine may exceed its capacity to produce it, and in these conditions glutamine may become "conditionally essential".

Glutamine is the largest store of amino acid in the body, with large amounts being stored in the muscle. Glutamine accounts for over 60% of the total intra-muscular amino acid pool. However, release rates are so high that even in resting muscle it is likely that all these stores would be used up within 7 hours if de-novo synthesis did not take place. During exercise release rates from muscle increase dramatically, leaving both muscle and plasma levels depleted for between hours and days depending on the duration and intensity of the exercise. Glutamine levels have been shown to be low in athletes with over training syndrome, and much recent research has focused on its role in the prevention of this syndrome.

Resistance to infection
Athletes in hard training are often prone to infections, particularly infections of the throat and the upper respiratory tract. There is mounting evidence that hard training can reduce immune function. Researchers have noted the parallels between the stress of hard training and the stress suffered by hospitalised trauma patients, particularly those suffering from burns. These patients are routinely given glutamine supplementation to protect glutamine status and this has been shown to improve immune function, similar benefits in athletic populations have been reported.

Optimal Muscle Growth
Glutamine is important for optimal muscle growth and adaptation. Animal studies suggest that glutamine stimulates protein synthesis and inhibits protein breakdown in muscles. In healthy subjects, infusing sufficient glutamine to double plasma glutamine concentrations has no effect on whole body proteolysis (protein breakdown), but slightly increases whole body synthesis. This may be due to the effect of glutamine on cell volume. Glutamine is taken up by the muscle cell thereby increasing the volume of the cell by drawing fluid into the cell due to the increase in intracellular osmolality. This may then promote muscle hypertrophy through the stimulation of Nitric-oxide Synthase in a similar way that a mechanical stretch influences gene expression. (Tidball et al 1999) Ensuring adequate muscle glycogen stores post exercise is another crucial factor in recovery and adaptation to exercise and glutamine has been shown to stimulate muscle glycogen synthesis from glucose.
Therefore ensuring adequate glutamine levels is essential in order to ensure optimal muscle function, muscle growth and resistance to infection.

How is it possible to maintain glutamine status?
Taking a protein supplement rich in glutamine in addition to carbohydrate, post exercise, may be sufficient to maintain glutamine status. (Van Hall et al 2000). Good products include Rego from Science in Sport who produce a version with a high concentration of glutamine peptide in addition to the standard soy protein isolate.
However, most post exercise protein carbohydrate products have a significant amount of calories, ideal in periods of hard training when it is crucial to maintain muscle glycogen stores, but there are times when it is useful to take glutamine in a less calorific form. This may include times after shorter intense workouts, during taper for competition and stressful situations not necessarily caused by training - e.g. injury and infection.
Glutamine is readily soluble in water and has a pleasant taste, so the easiest way to consume it is to dissolve a few grams of pure L-glutamine into water or your favourite cordial.
Many athletes have found it beneficial to use a 2-5g dose immediately after workouts and 2 hours post workout, with additional doses on an empty stomach either last thing at night or first thing in the morning in periods of heavy stress.

Who uses it?
Glutamine supplementation has found popularity with many top class swimmers, athletes and cyclists, in addition to body builders who have been fond of it for some time due to its positive effect on muscle volume.

Is it Vegetarian?

It is possible to obtain vegetarian L-glutamine. Glutamine usually manufactured by the controlled fermentation of glucose by a process involving the purification and crystalisation.

Glutamine as a marker of over training
Since maintaining adequate plasma glutamine levels is so important to optimal function, there has been much focus on using plasma glutamine levels as a marker of exercise stress and over training. Persons who are suspect or diagnosed with over training syndrome may benefit from monitoring plasma glutamine levels, particularly when training is being reintroduced.

Glutamine Testing as a marker of Over Training Syndrome

Some specialist Sport Clinics may undertake glutamine testing/ screening try;

Dr Richard Higgins
Health South
Don Valley Stadium
Sheffield. Tel. 0114 261 9990

History of Glutamine
1866 Glutamic Acid discovered by Ritthausen.
1883 Glutamine described by Schultze and Bosshard.
1914 Glutamine presence and possible functions described in Human Body Thierfelder and Sherwen
1934 Krebs demonstrates in vitro glutamine synthesis
1974 First reliable data available on intra cellular amino acid pools
1980s Glutamine shown to be an important fuel for gastro-intestinal tract and rapidly proliferating cells of the immune system
1990s Glutamine linked with over training syndrome, regulation of protein synthesis. Supplementation of hospitalised trauma patients becomes common practice. Athletes and body builders experiment with glutamine supplementation with good results. Glutamine shows promise as a marker of training status.

The future: Glutamine use in athletes set to increase and novel glutamine compounds developed. Mechanism which glutamine increases protein synthesis uncovered.


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