Glutamine is a building block of protein, which has many important functions: helping repair body tissues, keeping the digestive system working, and supporting the immune system.
Glutamine is what is known as a ‘conditionally essential’ amino acid. This means your body produces most of what it needs, but also gets some from foods. These include beef, pork, poultry, fish and shellfish; milk, yoghurt, cheese and eggs (especially egg whites); tofu, nuts, and legumes (like beans and lentils); vegetables such as spinach, cabbage (especially red cabbage), corn, and potatoes; and grains such as wheat, rice, and oats.
Given its many sources, glutamine deficiency is rare, but it does occur. You are at risk if you experience severe physiological stress such as traumatic injury, serious illness, surgery or major burns; a wasting disease such as HIV/AIDS or advanced cancer; or extreme endurance exercise. “High-intensity, prolonged athletic straining can temporarily deplete blood and muscle glutamine levels,” says Marie MacGregor, a registered dietitian based at the Sports Science Institute of South Africa.
A lack of glutamine availability can lead to slower muscle recovery, weakened immune function, and leaky gut in animal studies, but still needs further research, she says.
Who might benefit from glutamine supplementation?
Most people have enough glutamine, but if you are ill for a long period or have a severe injury, you may benefit from more. Ask your healthcare professional if a supplement could help; do not self-medicate. They can guide you on safety, and if appropriate, the right dosage for your specific needs.
While glutamine supplementation is considered safe in normal amounts, side effects may include bloating, stomach cramps, back pain, changes in bowel movements, constipation, headache, nausea, even liver toxicity1. The effects of taking glutamine long term are not yet fully known, but it may raise the risk of health problems.
“It’s not clear if healthy people with a reasonably balanced diet get any benefits from glutamine supplements,” says MacGregor.
The only use of glutamine approved by the US Food and Drug Administration is to reduce serious complications of sickle cell disease, an inherited blood disorder.
“Glutamine supplementation is used in hospitals for various conditions such as mucositis, wounds, mouth ulcers and graft vs host disease (a common side effect in people who receive cells from a donor), so it is used therapeutically in South Africa,” says MacGregor.
Possible training benefits of taking glutamine
• Accelerated muscle repair: Research suggests that by promoting protein synthesis, glutamine may speed up the repair of microtears in muscle fibre after intense exercise. According to a literature review2 in the journal Quality in Sport, “The evidence indicates that glutamine can support recovery processes by mitigating muscle inflammation, improving redox balance (cellular balance), and promoting anabolic signalling (the body’s cellular communication process for building, repairing, and growing tissues). However, the degree of effectiveness varies”.
• Reduced muscle soreness: Some studies3 suggest glutamine supplementation may lower circulating muscle damage markers in the bloodstream, helping diminish the severity of delayed onset muscle soreness.
• Immune system support: Strenuous physical activity temporarily suppresses immune function. Glutamine serves as a primary energy source for immune cells, which may help lower the risk of getting sick and prevent the onset of overtraining syndrome. However, 2026 review in the journal Medicina4 concluded that “Despite the widespread use of glutamine among athletes, scientific evidence supporting its efficacy is still limited”.
“Further research is needed before any recommendations can be made regarding glutamine use by athletes,” says MacGregor. “If athletes are meeting their protein requirements, there should be no additional need for glutamine. Avoid unnecessary supplements that are expensive but won’t provide a substantial benefit.”
References
1. https://pmc.ncbi.nlm.nih.gov/articles/PMC7069532/
2. https://www.researchgate.net/publication/390780968
_The_Role_of_Glutamine_in_Muscle_Regeneration_and
_Recovery_A_Literature_Review
3. https://pmc.ncbi.nlm.nih.gov/articles/PMC8234492/
4. https://pmc.ncbi.nlm.nih.gov/articles/PMC12942590/