Glutamine: What is it and who can benefit from it?

If you've ever been in a conversation about supplements that help with athletic performance, it's very likely you've heard of glutamine. This is a dietary supplement that has gained significant attention from the scientific community, athletes, and individuals seeking to boost their immune system or recover more quickly from stressful situations.

Let's take a detailed look at what glutamine is, where we can find it naturally, its benefits, and of course, who can benefit the most from it!

What is glutamine?

Glutamine is one of the 20 amino acids that make up proteins in the body. Although it is the most abundant amino acid in blood serum, its levels decrease in situations of intense physical stress. Under such conditions of intense stress, endogenous glutamine levels decrease to a point where supplemental intake may be beneficial.

Such situations may include:

Intense Exercise
Intense Stress
Chronic gastrointestinal disorder (e.g. IBS, Ulcerative Colitis, Celiac Disease, Dyspepsia)
Taking Medication
Treatment (e.g. chemotherapy, radiation therapy)
Combating pathological conditions (e.g. infections)

Or/and the combination of two of the above, for example, an athlete suffering from irritable bowel syndrome (IBS) who is required to "put out" an intense training load during the competitive season.

Glutamine & Mechanism of Action

Glutamine plays a multifaceted role in the body, participating in a multitude of physiological functions. Some of these include:

Protein synthesis
Protecting the intestinal walls
Strengthening the immune system
Production of antioxidants

The relationship between glutamine and glutathione is based on both biochemical and functional processes — glutamine is a key building block for the production of glutathione, one of the human body's most important antioxidants.

Support for muscles

It helps in the restoration and maintenance of muscle mass, as well as faster recovery from an impending injury.

Glutamine & Benefits

Considering the above, we can say that the main benefits of glutamine are related to two pillars: its possible beneficial action in improving recovery in cases of wounds, burns, and other bodily injuries, as well as its potential benefits to gastrointestinal health. More specifically, research has shown that it contributes to maintaining nitrogen balance, limiting protein loss. Only recently, studies on glutamine began to investigate the stress and catabolism caused by intense exercise. Additionally, regarding the relationship between glutamine and intestinal health, it appears that taking glutamine helps reduce intestinal permeability, inflammation, length of hospitalization, and mortality. Numerous studies highlight glutamine and its possible contribution to reducing symptoms of irritable bowel syndrome (IBS), especially when combined with a low FODMAP diet. Although it did not appear to have a significant effect on Crohn's disease, it is worth noting that in most related studies, the sample size was small, which limits the reliability of the conclusions.

Additionally, some of the available scientific data we have at this time suggest that glutamine may have an effect on enhancing the function of the immune system and reducing the likelihood of infections in adults undergoing abdominal surgery, as it appears to help increase the production of white blood cells.

Additionally, it has been proven that glutamine is a key component for brain function, as it serves as a precursor molecule for the synthesis of the neurotransmitters glutamate and gamma-aminobutyric acid (GABA). In the brain, glutamine is converted to glutamate, which is the primary excitatory neurotransmitter associated with learning and memory. In specific neurons, glutamate is converted into GABA, the primary inhibitory neurotransmitter that helps promote relaxation and reduce anxiety. This process ensures the proper balance between stimulation and inhibition in the brain. Although supplemental glutamine does not easily cross the blood-brain barrier, it can indirectly contribute to the synthesis of these neurotransmitters by supporting metabolism, particularly during times of stress or illness when glutamine levels are reduced.

Finally, there is not yet sufficient scientific data to show clear benefits to athletic performance.

Glutamine & natural foods. What are the richest sources?

Glutamine is found mainly in foods with high protein content, both from animals and plants.

Sources of glutamine from animals include: various types of meat (such as beef, chicken, pork, lamb, and turkey), fish and seafood (such as salmon, tuna, cod, herring, anchovies, and halibut), eggs (one large egg has about 0.6 grams of glutamine), and dairy products (such as milk, yogurt - especially Greek yogurt which has a lot of protein -, cottage cheese, ricotta, and Parmesan).
Sources of glutamine from plants include: legumes (such as soybeans, chickpeas, lentils, and various types of beans), grains (such as white rice, corn, and oats), vegetables (such as red cabbage, which is considered a very good source, spinach, parsley, and beets), nuts and seeds (such as almonds, walnuts, cashews and peanuts), spirulina, and tofu.

It is important to know that the exact amount of glutamine in food can change depending on how we process and cook it. However, a diet with a variety of these foods usually meets the body's needs for glutamine when we are healthy.

In what forms do we encounter it?

There are many glutamine dietary supplements that vary in both content and form. Primarily, these products are available in:

Powder
Capsule
Tablets
Drinking solution

The most common form is L-glutamine, 500mg per capsule or tablet.

Glutamine & usual dosage. How much and when to take glutamine?

No specific daily recommended amount (RDA) of glutamine has been established because our body produces it on its own.However, in some cases, levels can drop, and taking a supplement can help. The amount of supplement someone needs depends on their health and the reason they are taking it. Therefore, the dosage can vary greatly depending on the case. Typically, it is recommended that we gradually increase the amount we take so that the body can more easily get used to the supplement, while taking large doses should only be done under the supervision of a doctor.

Typically, it is recommended to start with a daily dose of glutamine between 500 mg and 2 g.Then, you can take 2 to 5 g twice a day.

Another way to calculate the appropriate dose for a healthy person is to take 50 mg of L-glutamine per kilogram of body weight.

It is important to remember that glutamine may also be contained in other dietary supplements you may be taking, such as protein powders. In this case, you should also take this quantity into account.

Amino acids like glutamine are recommended to be taken on an empty stomach, usually between meals at any time of the day. Finally, it is worth mentioning that it is not recommended to take it with hot beverages.

Finally, it appears that L-glutamine may work synergistically with certain dietary supplements, particularly those related to muscle recovery, as well as gut health and development.

Dietary Supplement	Potential Synergistic Effect with L-Glutamine	Who May Benefit	Notes
Protein powders (Whey, Casein, Soy)	Enhanced muscle recovery and growth, possibly better glycogen replenishment.	Athletes, individuals in recovery periods.	Many protein powders already contain glutamine.
BCAAs (Branched-Chain Amino Acids)	Reduced muscle catabolism, improved post-exercise recovery.	Athletes engaged in endurance sports or high-intensity training. Individuals under high physical or psychological stress. People recovering from injury or surgery.	Often combined in sports supplements.
Creatine	Possible enhancement in muscle growth and strength; may aid digestive comfort for some creatine users.	Athletes involved in high-intensity training.	More research is needed.
Probiotics	Support for gut health, improved nutrient absorption, and immune function.	Individuals with digestive issues or inflammatory bowel conditions.	Glutamine serves as a fuel source for intestinal cells.
Zinc & Vitamin A	Possible improvement in gut barrier function and support for growth (especially in malnourished individuals).	Individuals with digestive issues or inflammatory bowel conditions. Vegetarian and vegan individuals who may not get adequate amounts through diet.	Observed in specific population groups.

However, it is important to assess your individual needs and the potential effects of combining supplements. To ensure safety and effectiveness, it is advisable to consult a doctor or a qualified dietitian before using supplements in combination.

Does glutamine have side effects?

Glutamine typically does not cause adverse effects. Even doses as high as 50–60 grams per day taken for several weeks appear to be well tolerated by humans without causing side effects.
Of course, supplemental intake is contraindicated in certain individuals—unless otherwise instructed by their treating physician—with the most notable cases being:

Individuals with kidney or liver failure
People with psychiatric disorders
Those with a history of seizures
Cancer patients
Pregnant and breastfeeding women
Children under 18 years of age

Conclusion – Who might benefit from glutamine consumption?

Glutamine is an important amino acid with a wide range of beneficial effects on the body, contributing to overall health. A healthy lifestyle combined with appropriate glutamine intake can lead to noticeable improvements in both physical and mental well-being.

Scientific References

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Amirhossein Ramezani Ahmadi, Elham Rayyani, Mehdi Bahreini, Anahita Mansoori, The effect of glutamine supplementation on athletic performance, body composition, and immune function: A systematic review and a meta-analysis of clinical trials, Clinical Nutrition, Volume 38, Issue 3, 2019, Pages 1076-1091, ISSN 0261-5614.

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Perna S, Alalwan TA, Alaali Z, Alnashaba T, Gasparri C, Infantino V, Hammad L, Riva A, Petrangolini G, Allegrini P, Rondanelli M. The Role of Glutamine in the Complex Interaction between Gut Microbiota and Health: A Narrative Review. Int J Mol Sci. 2019 Oct 22;20(20):5232. doi: 10.3390/ijms20205232. PMID: 31652531; PMCID: PMC6834172.

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