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Inhaltsstoff-Glossar
Glutamine
What Is Glutamine?
Glutamine is one of the 21 proteinogenic amino acids that the body uses to build proteins. It contains a chiral center, which means it exists as L-glutamine and D-glutamine. However, only L-glutamine occurs in proteins. Therefore, when we refer to glutamine, we mean L-glutamine. L-glutamine is considered a non-essential amino acid because the human body can synthesize it when needed.
Glutamine accounts for approximately 20% of all amino acids circulating in the bloodstream, making it one of the most abundant amino acids in the body. It is a central metabolite in the metabolism of all living organisms. Glutamine supplementation is particularly popular among athletes, as it is believed to promote muscle growth and support the immune system.
Glutamine accounts for approximately 20% of all amino acids circulating in the bloodstream, making it one of the most abundant amino acids in the body. It is a central metabolite in the metabolism of all living organisms. Glutamine supplementation is particularly popular among athletes, as it is believed to promote muscle growth and support the immune system.
Where Does Glutamine Naturally Occur?
Consistent with glutamine's central role in the metabolism of most living organisms, it is naturally present in relatively high amounts in many foods. Soybeans, cheese, peanuts, spelt, and mung beans each contain more than 4 g of glutamine per 100 g. Within the human body, glutamine is particularly abundant in skeletal muscle tissue and muscle cells, where it can also be synthesized directly.
What Is the Primary Function of Glutamine in the Body?
The amino acid glutamine serves as both a building block and a substrate for proteins, immune cells, cells of the gastrointestinal tract, and liver cells. In addition, glutamine is a universal donor of amino groups in metabolism. Chains consisting of several glutamine molecules are components of important transcription factors, including FOXP2.
During injuries, burns, surgical procedures, and other situations associated with severe physiological stress, glutamine concentrations in muscle cells decrease by up to 50%. Researchers have observed this effect regardless of nutritional intake. This led to the assumption that glutamine is a conditionally non-essential amino acid that becomes indispensable during periods of illness, injury, and advanced age.
One of the earliest discoveries regarding muscle cell physiology was that glutamine increases the volume of muscle cells during physical stress by promoting water retention. This is considered an anabolic signal that supports glycogen storage and protein synthesis. Glutamine is also indispensable for the immune system. Various immune cells use glutamine as a primary nutrient and, in fact, consume even more glutamine than they do glucose, the body's primary cellular fuel.
During injuries, burns, surgical procedures, and other situations associated with severe physiological stress, glutamine concentrations in muscle cells decrease by up to 50%. Researchers have observed this effect regardless of nutritional intake. This led to the assumption that glutamine is a conditionally non-essential amino acid that becomes indispensable during periods of illness, injury, and advanced age.
One of the earliest discoveries regarding muscle cell physiology was that glutamine increases the volume of muscle cells during physical stress by promoting water retention. This is considered an anabolic signal that supports glycogen storage and protein synthesis. Glutamine is also indispensable for the immune system. Various immune cells use glutamine as a primary nutrient and, in fact, consume even more glutamine than they do glucose, the body's primary cellular fuel.
What Are the Benefits of Glutamine Supplementation?
To date, the European Food Safety Authority (EFSA) has not approved any health claims for glutamine as a dietary supplement. At the time of its assessment, the available clinical evidence was considered too inconsistent. However, this evaluation was published several years ago, and additional research on glutamine supplementation has since become available.
Researchers investigated the hypothesis that glutamine supplementation may prevent the decline of intracellular glutamine concentrations during periods of increased inflammation, thereby improving health outcomes. A small number of studies reported benefits for patients receiving glutamine supplementation. In particular, patients suffering from severe inflammatory conditions experienced lower infection rates and shorter hospital stays. However, a six-month clinical trial involving approximately 1,200 critically ill patients questioned whether glutamine supplementation is beneficial in every clinical situation. In that study, glutamine supplementation was associated with a significantly increased mortality rate. Researchers therefore continue to debate whether declining glutamine concentrations represent a true deficiency or rather an adaptive physiological response.
Another argument against glutamine supplementation is that many types of cancer depend on glutamine. Cancer cells generally consume considerably more glutamine than healthy cells. Consequently, laboratory culture media used for growing tumor cells typically contain high concentrations of glutamine.
With regard to athletic performance, clinical studies have shown that glutamine supplementation may reduce fatigue, enhance glycogen synthesis and recovery, decrease post-exercise cortisol release, and reduce the accumulation of toxic metabolic by-products such as ammonia. However, particularly concerning athletic performance and muscle growth, the available scientific evidence remains inconsistent.
Several studies have demonstrated positive effects of glutamine supplementation in older adults, including improvements in leg muscle performance and other aspects of physical function. Overall, glutamine is considered an interesting longevity molecule because researchers suspect that cellular glutamine availability may become insufficient with advancing age.
Many clinical studies have used well-tolerated daily doses ranging from 5 g to 15 g of glutamine. Nevertheless, conflicting findings also indicate that the optimal dosage still requires further investigation. One scientific review concluded that high daily intakes of approximately 40 g of glutamine may impair amino acid metabolism or interfere with the body's own glutamine synthesis. In contrast, clinical guidelines in other settings recommend administering 0.3–0.5 g of glutamine per kilogram of body weight—which corresponds to approximately 40 g per day for an individual weighing 80 kg.
References
Further information and scientific studies on the active ingredient glutamine can be found here.
Assessment of the Safety of Glutamine and Other Amino Acids
www.pubmed.ncbi.nlm.nih.gov/11533313