Glutamine is the most abundant amino acid in the human body. It plays a crucial role in many physiological processes.
For athletes and active individuals, glutamine is of particular interest due to its potential effects on muscle recovery, the immune system, and performance.
Let's examine what scientific research tells us about this topic.
What is glutamine?
Glutamine is a non-essential amino acid, which means that the body can produce it on its own. This amino acid is not part of the BCAAs, which include valine, leucine, and isoleucine.
It is the most abundant free amino acid in blood plasma and muscle tissue. Glutamine plays a crucial role in many physiological processes, including cellular metabolism, immune system function, and maintaining the integrity of the intestinal wall.
Glutamine serves as the primary energy source for rapidly dividing cells, such as those in the immune system and the intestine.
It also participates in protein synthesis, nitrogen transport between organs, and regulation of acid-base balance.
In situations of intense physical stress, such as during prolonged exercise or serious illness, the demand for glutamine may exceed the body's production capacity, which may require additional external supplementation.
Effects on muscle recovery
Several studies have examined the impact of glutamine supplementation on muscle recovery after exercise. A meta-analysis published in 2019 in Clinical Nutrition analyzed47 clinical trials on the effects of glutamine in athletes.
The results showed no significant effect on aerobic performance (VO2max) orbody composition. However, certain physiological effects were observed, such as higher blood sugar levels after exercise and a reduction in blood neutrophils.
Another systematic review published in 2018 in Nutrients2examined the role of glutamine as an anti-fatigue amino acid. The authors concluded that glutamine could improve certain parameters related to fatigue, such as a reduction in ammonia production and an increase in glycogen.
However, these effects did not necessarily translate into measurable improvements in performance.
Impact on the immune system
Glutamine is often touted as beneficial for athletes' immune systems. Here's what the research says on the subject:
A randomized controlled trial published in 2015 in the International Journal of Clinical Pharmacology andTherapeutics3examined the effect of glutamine supplementation on immune function during intensive training.
The results showed a significant increase in T lymphocytes and a decrease in symptoms of upper respiratory tract infections in the group supplemented with glutamine.
However, the 2019 meta-analysis mentioned above did not prove any significant overall effect of glutamine on athletes' immune systems. These contradictory results highlight the need for further research in this area in order to understand the actual mechanisms involved.
Effects on gut health
Glutamine is also being studied for its potential effects on gut health, which could indirectly affect athletic performance.
A review published in 2017 in the International Journal of MolecularSciencesexamined the role of glutamine in intestinal health. The authors concluded that glutamine plays a central role in maintaining the integrity of the intestinal wall and may be beneficial in the treatment of certain gastrointestinal disorders.
However, no specific studies on the intestinal tract have been conducted on a population of athletes, which limits the conclusions we can draw about this type of audience.
Frequently asked questions about glutamine
Can you run out of glutamine?
Yes, glutamine deficiency can occur, particularly in patients who are seriously ill or under significant physical stress.
How can you identify a glutamine deficiency?
Deficiencies are mainly identified through blood tests that measure plasma glutamine concentrations.
A concentration below 420 μmol/L may indicate a deficiency.5. However, there is no clear consensus on threshold values, as glutamine levels vary depending on metabolic status.
Athletes who participate in intense endurance sports may also experience temporary decreases in glutamine after exercise.6. A deficiency can affect cellular function, particularly in the immune system and intestinal wall.
Does whey contain glutamine?
Glutamine is naturally present in whey proteins. It is a non-essential amino acid found in relatively large quantities in whey.
Typically, a standard 30g serving of whey generally provides around 4g of glutamic acid, from which glutamine is derived.
However, the exact content may vary depending on the type of whey (concentrate, isolate, hydrolysate) and the manufacturing process. Whey isolate tends to have a slightly higher concentration of glutamine than concentrate.
Which food is richest in glutamine?
Among common foods, cottage cheese is one of the best dietary sources of glutamine.7. Meats such as beef and chicken also have a significant concentration of this amino acid.
However, the exact content may vary depending on the preparation methods. It is important to note that glutamine is a non-essential amino acid that the body can produce, so a balanced diet is usually sufficient to maintain adequate levels in healthy individuals.
What are the side effects of glutamine?
Glutamine is generally well tolerated when consumed as part of a normal diet or as a supplement in moderate doses.
However, side effects may occur, especially at high doses or over a long period of time. Potential side effects include gastrointestinal disorders such as nausea, bloating, or stomach pain.8.
In rare cases, excessive intake can disrupt the balance of amino acids in the body. In cancer patients, glutamine supplementation should be considered with caution as it could theoretically promote tumor growth, although scientific evidence on this remains limited.9.
For individuals with pre-existing health conditions, it is recommended to consult a healthcare professional before taking any supplements.
Conclusion
Although glutamine is involved in many important physiological processes, scientific evidence of its beneficial effects on athletic performance and recovery remains mixed and inconclusive at this stage.
Some studies show promising effects, particularly on gut health and certain aspects of immune function, but others do not show any significant benefits.
It is important to note that most studies were conducted over relatively short periods and with limited samples.
Further research, particularly long-term, large-scale clinical trials, is needed to better understand the effects of glutamine supplementation in athletes.
In the meantime, we encourage athletes interested in glutamine supplementation to consult a healthcare professional or sports nutritionist for personalized advice tailored to their specific needs.
Sources
2Glutamine as an Anti-Fatigue Amino Acid in Sports Nutrition by Coqueiro, A. Y., Rogero, M. M., & Tirapegui, J.
3Glutamine supplementation and immune function during heavy load training by Song, Q. H., Xu, R. M., Zhang, Q. H., Shen, G. Q., Ma, M., Zhao, X. P., … & Wang, Y.
4The Roles of Glutamine in the Intestine and Its Implication in Intestinal Diseases by Kim, M. H., & Kim, H.
