L-Glutamine

Synonym(s): glutamine

Nutrient group: Amino acids

Sources and physiological effects

Dietary sources
The proteinogenic amino acid L-glutamine is the most abundant unbound amino acid in the human body and is considered conditionally essential. Under certain circumstances - such as injuries, burns, operations or serious illnesses - endogenous synthesis may be inadequate and external supply may be necessary. L-glutamine is present in both bound and free form in the diet. Foods with a high glutamine content include, cheese, meat, soybeans, peanuts and oat flakes.
Physiological effects
Energy metabolism	Energy substrate of the cells of the gastrointestinal tract maintenance of a healthy intestinal mucosa
Immune system	Energy substrate of lymphocytes Differentiation of B-cells IL-1 secretion of macrophages
Muscle building	Protein synthesis and amino acid homeostasis
Antioxidant	Precursor for the most important endogenous antioxidant glutathione
Kidney	Regulation of acid-base balance Nitrogen supplier for the production of ammonium.

Recommended intake

Requirement
Group with increased demand	Radiotherapy, cytostatics, NSAID, malnutrition, premature babies, high physical strain (sports), liver and kidney diseases, pancreatitis, burns and injuries
Special groups at risk of deficiency	Athlete, tumor patients, trauma patients

Recommended intake according to food labelling regulations (=100 % TB marking on label)
		N/A
Nutrient safety
UL	Long-term daily intake at which no negative health effects are to be expected	N/A
NOAEL	Maximum intake, with no observed adverse effect	N/A
Highest Observed Intake (HOI)	Highest dosage published in studies without negative effects (unofficial value)	14 g/d

Detailed information

L-glutamine for intestinal mucosa integrity

The conditionally essential amino acid L-glutamine plays a central role in the development and maintenance of cell systems. Cells with high division rates, such as the mucosa cells of the small intestine, depend on an adequate supply of glutamine. The mucosa cells metabolize about 70% of the glutamine absorbed, making this amino acid an indispensable nutrient for maintaining intestinal permeability (1). Furthermore, L-glutamine is the precursor for glutathione biosynthesis and thus a central component for maintaining antioxidative status.

L-glutamine - therapeutic for damaged intestinal mucosa

In a disturbed intestinal mucosa, targeted glutamine supplementation has demonstrated therapeutic effects. In animal experiments, a restoration of the intestinal mucosa (measured by increased intestinal mucosa weight and increased mucosal DNA) as well as an improvement of the microvilli height and crypt depth could be observed (2). In addition, glutathione levels in the jejunum normalized without any significant change in glutathione levels in other tissues. (3). Supplementation with L-glutamine can also maintain the defensive functions of the intestinal mucosa and support the intestine-associated immune response. In children with diarrhea, the duration of the disease was significantly reduced by the additional administration of L-glutamine, which is attributed to the improved defensive performance of the mucosa (4).

L-glutamine in Helicobacter pylori infections

New studies point to a protective effect of L-glutamine in Helicobacter pylori infections. H. pylori infection is considered the main cause of gastric ulcer and a high-risk factor for gastric carcinoma and MALT lymphoma. L-glutamine neutralizes the ammonia produced by the bacterium and thus prevents cell damage. The mucosa damage caused by H. pylori could be reduced by the targeted supplementation of L-glutamine. In addition, a more effective immune response and a lower degree of inflammation were observed (5).

Mucosa damage from medication

An increased intestinal permeability and mucosal damage in the gastrointestinal tract are often observed when taking NSAIDs such as indomethacin or diclofenac regularly. The gastrointestinal tolerance can be improved by accompanying supplementation with L-glutamine, ideally 30 minutes before taking the medication (6).

Glutamine supplementation in endurance athletes

Sport activity influences the amino acid composition in the plasma. After intensive training, glutamine levels are reduced by up to 30% (7). To restore the glutamine concentration in the blood, stored glutamine is released from the muscle. This can lead to a reduction in muscle protein and thus to a reduction in muscle mass. On the other hand, a sufficient glutamine supply at the right time, increases muscle growth even under physical strain, prevents the reduction of muscle mass and delays muscle fatigue (1). Endurance sports and intensive short-term exercise also lead to an increase in ammonia levels in the plasma, which has toxic effects on the central nervous system. A regular and high intake of L-glutamine was shown to prevent hyperammonemia in football players and improve the excretion of toxic metabolites (8).
The drop in glutamine levels in the plasma during and after exercise adversely affects the immune functions of endurance athletes. Since glutamine serves as the primary energy source for immunocompetent cells, it is assumed that the reduced glutamine status is partly responsible for the increased susceptibility of endurance athletes to infections (9).

L-glutamine in disease, injury and recreation

L-glutamine is one of the conditionally essential amino acids that can attain essentiality under certain conditions and disease states. A low glutamine level is observed in serious illnesses and injuries. Under catabolic conditions typical of severe trauma, burns or surgery, the body's own glutamine synthesis is not sufficient to meet the increased requirements(10). If no glutamine is supplemented, a negative glutamine balance occurs, which weakens the immune system, since L-glutamine serves the immune cells (lymphocytes, macrophages and neutrophilic granulocytes) as an energy source. A targeted increased intake, on the other hand, can improve the prognosis and the healing success via immunological processes (11). L-glutamine levels are also lowered for 2 – 7 days post injuries and surgical procedures. This increases the permeability of the intestinal mucosa and reduces the effectiveness of the bacterial defense functions. This is considered to be one of the causes of an increased risk of bacterial infection after surgery (12)

Deficiency symptoms

Impact on	Symptoms
General well-being	Diminished physical performance, extended convalescence
Immune system	Extended convalescence, general susceptibility
Muscles	Decrease in muscle mass, muscle weakness
Gastrointestinal system	Impairment of the intestinal mucosa, Leaky Gut Syndrome, villous atrophy

Indications

Effect	Indication	Dosage
Physiological effects at a low intake	Complementary therapy for inflammatory diseases of the gastrointestinal tract, especially of the intestinal mucosa and for Helicobacter pylori infections	2 - 10 g/d
	To improve the tolerability of antirheumatic drugs and antiphlogistics (NSAIDs)	5 - 10 g/d
	To maintain and increase muscle mass in performance athletes	10 - 20 g/d
	For improvement of immune function, to reduce the frequency of infection in endurance athletes and people under physical strain	10 - 20 g/d
	Complementary therapy for injuries and surgical procedures to maintain immune function and improve prognosis	15 - 40 g/d

Administration

General mode of administration
When	L-glutamine should be taken between meals.
	Notes: If NSAID is to be taken, take L-Glutamin 30 minutes before. For competitive athletes take both before and after training or competition.
Side effects
No side effects are known to date.
Contraindications
No contraindications are known to date.

Interactions

Drug interactions
NSAIDs (e.g. diclofenac, ASS, ibuprofen)	Gastrointestinal side effects (e.g. mucosal damage) can be reduced by taking glutamine in parallel.
Tumor therapy in general	Glutamine supports the immune system and has protective effects on intestinal function.
Nutrient interactions
None	No relevant interactions are known to date

Description and related substances

Description

Proteinogenic, non-essential amino acids

Related substances

L-glutamine

References

1) Gröber, U. 2002. Orthomolekulare Medizin. Ein Leitfaden für Apotheker und Ärzte.
2) Sukhotnik, I. et al. 2007. Dietary glutamine supplementation prevents mucosal injury and modulates intestinal epithelial restitution following ischemia-reperfusion injury in the rat. Dig Dis Sci. 52(6):1497-504.
3) Belmonte, L. et al. 2007. Effects of glutamine supplementation on gut barrier, glutathione content and acute phase response in malnourished rats during inflammatory shock. World J Gastroenterol. 13(20):2833-40.
4) Yalcin, S. S. et al. 2004. Effect of glutamine supplementation on diarrhoea, interleukin-8 and secretory immunoglobulin A in children with acute diarrhoea. J Pediatr Gastrenterol Nutr. 38(5):494-501.
5) Hagen, S. J. et al. 2009. Inflammation and foveolar hyperplasia are reduced by supplemental dietary glutamine during Helicobacter pylori infection in mice. J Nutr. 139(5):912-8.
6) Gröber, U. 2007. Arzneimittel und Mikronährstoffe. Medikationsorientierte Supplementierung.
7) Blomstrand, E., Essén-Gustavsson, B. 2008. Changes in amino acid concentration in plasma and type I and type II fibres during resistance exercise and recovery in human subjects. Amino Acids.
8) Bassini-Cameron, A. et al. 2008. Glutamine protects against increases in blood ammonia in football players in an exercise intensity-dependent way. Br J Sports Med. 42(4):260-6.
9) Hahn, A. et al. 2005. Ernährung. Physiologische Grundlagen, Prävention, Therapie.
10) Cander, B. et al. 2005. Effects of glutamine in critical illness. Saudi Med J. 26(6):969-73.
11) Newsholme, P. 2001. Why is L-glutamine metabolism important to cells of the immune system in health, postinjury, surgery or infection? J Nutr. 131(9 Suppl):2515S-22S.
12) Zhang, W. B, Jiang, H. P. 2009. Intestinal mucosal barrier dysfunction after abdominal operation and its clinical significance. Nan Fang Yi Ke Da Xue Xue Bao. 29(2):246-9.

References Interactions
Stargrove, M. B. et al. Herb, Nutrient and Drug Interactions: Clinical Implications and Therapeutic Strategies, 1. Auflage. St. Louis, Missouri: Elsevier Health Sciences, 2008.
Gröber, U. Mikronährstoffe: Metabolic Tuning –Prävention –Therapie, 3. Auflage. Stuttgart: WVG Wissenschaftliche Verlagsgesellschaft Stuttgart, 2011.
Gröber, U. Arzneimittel und Mikronährstoffe: Medikationsorientierte Supplementierung, 3. aktualisierte und erweiterte Auflage. Stuttgart: WVG Wissenschaftliche Verlagsgesellschaft Stuttgart, 2014.