L-Glutamine

The Benefits of Glutamine

• What is Glutamine?
• Who Should Consider Taking L-Glutamine Supplements?
• Summary of Glutamine's Physiological Effects
• L-Glutamine Research
• Is Glutamine effective?
• How to take L-Glutamine
• Glutamine References

What is Glutamine?  L-Glutamine is the most abundant amino acid in the human body making up over 50% of the total amount of amino acids.  It is essential for growth and is known to play an important role in liver function, serves as an important fuel for many tissues in the body (particularly the muscles, immune cells, and the gastrointestinal tract, and plays a role in the regulation of protein synthesis (Rennie et al., 1989).  In fact glutamine is regularly used by doctors and health professionals to treat illness, injury and infection (smith, 1990).

Who Should Consider Taking L-Glutamine supplements?  Anyone who trains intensively, or for prolonged periods of time may benefit from glutamine supplements.  Strength/power athletes and endurance athletes like runners and footballers should all benefit from glutamine supplements.

Summary of Glutamine's Phyiological Effects:

• Improved immune function and reduced risk of infection
• Increased levels of growth hormone
• Helps to maintain the amino acid balance
• Enhanced protein synthesis
• Improves the rate of recovery

L-Glutamine Research  All though our bodies are able to produce glutamine from other amino acids in our diet, stores of glutamine are quickly depleted during times of stress or intense physical activity.  During periods of intense stress, such as, prolonged or intense exercise, starvation, or trauma, the level of plasma glutamine may decrease substantially (Castell, 2003).  Intense exercise or any period of prolonged stress can deplete glutamine levels. Regular exercise has been shown to deplete glutamine levels by 45% in just 7 days (Newsholme, 1994).  Following Marathon running plasma glutamine levels have been shown to decrease by around 20% (Castell and Newsholme, 1997).  Since glutamine is an important fuel for immune cells, when glutamine levels are low, there is an increased risk of infection.

The consumption of oral glutamine has been shown to have a beneficial effect on immune function, and reduces the risk of infection following prolonged endurance exercise (Castell and Newsholme, 1997; Castell, 2003) and should be of benefit to athletes engaged in heavy exercise training (Antonio and Street, 1999).

Most important to the athlete is glutamine's ability to increase the production of protein (muscle building) and decrease protein degradation (muscle breakdown). Glutamine helps to maintain the amino-acid balance in the body, thereby enabling a greater synthesis of protein and a possible decrease in symptoms of overtraining (Bompa et al., 2003).  Glutamine stimulates the synthesis of new protein within muscle cells, this in turn will lead to an increase in the size and strength of the muscles.  This increase in strength is partly due to glutamines muscle cell volumising effect, whereby there is increased retention of water within muscle cells.

Because glutamine can be used as an energy source, maintaining a high level of glutamine in muscle tissue may help to preserve the valuable stores of muscle glycogen (carbohydrate store within muscle tissue).  It will also help to increase the rate of glycogen re-synthesis in muscle cells, following strenuous or prolonged exercise.

Glutamine supplementation may efficiently lead to the release of growth hormone (Bompa et al., 2003). In fact, it is known that just a 2 gram dose of L-glutamine, taken orally, can double the level of growth hormone in just 30 minutes (Welbourne, 1995).  When glutamine levels rise in the blood, it is detected by the brain.  The brain associates this rise in glutamine levels with an increase in acidity in the blood and releases growth hormone in order to regulate the acidity levels.

In short, glutamine supplementation aids recovery from prolonged or intense exercise, primarily, by reducing the rate of muscle breakdown within muscle tissue. It also aids immune function, spares valuable stores of glycogen, and increases levels of growth hormone.

Is Glutamine effective?  Glutamine appears to be effective at preventing amino acid depletion and enhances post exercise immune function.

How to take L-Glutamine?  Health professionals generally recommend a daily dosage of 5-10 grams of glutamine, split into 2-4 servings.  Athletes would be wise to use a minimum dose of 2 grams in order to gain the benefit of increased growth hormone levels.  Ideally this should be taken 30 minutes prior to exercise and again immediately after exercise.

References

Antonio, J. and Street, C. (1999) Glutamine: a potentially useful supplement for athletes. Can J Appl Physiol. 24 (1), 1-14. 

Bompa, T. O., Pasquale, M. D. and Cornacchia, L. J. (2003) Chapter 6: Using Nutritional Supplements. In: Serious Strength Training. Human Kinetics. Leeds, United kingdom. 

Castell, L. (2003) Glutamine supplementation in vitro and in vivo, in exercise and in immunodepression. Sports Medicine. 33 (5), 323-345. 

Castell, L. M. and Newsholme, E. A. (1997) The effects of oral glutamine on athletes after prolonged, exhaustive exercise. Nutrition. 13 (7-8), 738-742. 

Newsholme, E. A. (1994) Biomechanical mechanisms to explain immunosuppression in well-trained and overtrained athletes. International Journal of Sports Medicine. 15, S142-147. 

Rennie, M. J., MacLennan, P. A., Hundall, H. S. et al., (1989) Skeletal muscle glutamine transport, intramuscular glutamine concentration, and muscle-protein turnover. Metabolism. 38 (8 Suppl 1), 47-51. 

Smith, R. J. (1990) Glutamine metabolism and its physiologic importance.  Journal of Parenatal and Eternal Nutrition. 14, 40S-44S. 

Welbourne, T. C. (1995) Increased plasma bicarbonate and growth hormone after an oral glutamine. American Journal of Clinical Nutrition. 61, 1058-1061.