Glutamine

Inhaltsstoff-Glossar

Glutamine

What is glutamine?

Glutamine is one of the amino acids the body uses to build proteins. When we speak of glutamine in human nutrition, we generally mean L-glutamine.

It is the most abundant free amino acid in human blood and muscle tissue and is a central metabolite in many organisms. Under normal conditions, the body can produce sufficient amounts, so glutamine is classified as nonessential.

Where does glutamine occur naturally?

Glutamine is found in many protein-rich foods. Sources include:

  • Soy products
  • Cheese
  • Peanuts
  • Spelt
  • Mung beans
  • Meat and fish

Within the body, glutamine is stored primarily in skeletal muscle and can be synthesized directly by muscle cells.

What is glutamine’s primary function?

Glutamine serves several functions:

  • Building block for proteins
  • Fuel for immune cells
  • Fuel for cells of the intestinal lining
  • Nitrogen transport between tissues
  • Precursor for nucleotides and other molecules
  • Contribution to acid-base regulation in the kidneys

Immune cells and intestinal cells can consume large amounts of glutamine, particularly during infection, injury or severe metabolic stress.

When does glutamine become conditionally essential?

After surgery, burns, trauma or critical illness, glutamine concentrations in muscle may decline markedly. In such situations, endogenous production may no longer meet demand.

This has led to the description of glutamine as a conditionally essential amino acid during severe illness. Whether supplementation is beneficial depends strongly on the clinical situation.

Glutamine in intensive-care medicine

Early studies suggested that glutamine supplementation might reduce infections or shorten hospital stays in selected patients. Later large clinical trials produced more cautious or even unfavorable findings in critically ill people.

High-dose glutamine given to patients with organ failure or severe critical illness was associated with increased mortality in one major study. For this reason, glutamine should not be used indiscriminately in intensive-care settings.

Glutamine and cancer

Many cancer cells use glutamine at a high rate. This has led researchers to study glutamine metabolism as a potential therapeutic target.

This does not mean that normal dietary glutamine causes cancer. However, people with active cancer should not take high-dose glutamine supplements without discussing them with their oncology team.

Glutamine and exercise

Glutamine is popular among athletes and is marketed for muscle growth, recovery and immune support. Clinical studies have examined its effects on:

  • Fatigue
  • Glycogen synthesis
  • Post-exercise recovery
  • Cortisol
  • Ammonia accumulation
  • Immune function after intense exercise

Results are inconsistent. In healthy people who already consume enough protein, glutamine generally does not produce a clear increase in muscle mass or strength.

Dosage and safety

Studies often use doses of approximately 5–15 g per day. Higher amounts have also been used in clinical settings, but the optimal dose remains uncertain.

Very high intakes may alter amino-acid metabolism or reduce the body’s own glutamine synthesis. People with liver disease, kidney disease, cancer or severe illness should use glutamine only under professional supervision.

Conclusion

Glutamine is a central amino acid for muscle, immune and intestinal metabolism. It may become conditionally essential during severe stress. Supplementation has selected clinical applications, but evidence for routine use in healthy athletes or for longevity remains inconsistent.

Sources