Glutamine is a popular dietary supplement in bodybuilding, taken in free form primarily for further stimulation of muscle growth and increase in muscle strength, as well as for strengthening the immune system and.. weight loss.
Glutamine belongs to a broad class of controversial sports supplements, the effectiveness of which lacks unequivocal scientific evidence.
In this material, we will examine what scientists say about the benefits/ineffectiveness of glutamine, its uses in bodybuilding and medicine, in which natural products it is found, and what potential harm it may pose to health when taken in high doses.
Main thoughts:
Glutamine can reduce cravings for sweets
Taking glutamine does not affect muscle strength and endurance
What is glutamine?
Glutamine is a non-essential amino acid that is part of almost any protein. It is sometimes referred to as “conditionally essential” in the context of certain diseases.
Vegans and vegetarians who do not consume animal products (dairy, fish, meat, eggs) are also at risk of its deficiency.
Since glutamine is the amino acid with the highest relative proportion in muscle composition, it is often recommended for bodybuilding to accelerate recovery after workouts and promote muscle growth.
Glutamine, like many other amino acids, is sold as a special sports supplement. In its natural form, it is found in large quantities in animal products: lean meat and eggs. It is also very rich in whey protein and casein.
In addition, glutamine plays a very important role in the function of the immune system and intestines.
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What is glutamine used for? Scientists’ reviews on its effectiveness
As we mentioned, glutamine is a conditionally essential amino acid, and its importance increases in certain conditions 2,3 associated with muscle mass loss or muscle damage that require active immune protection: injuries, burns, muscle damage from stab wounds, diseases accompanied by muscle tissue breakdown, such as AIDS.
In these conditions, the consumption of glutamine helps to preserve and promote muscle mass growth.
Of all the amino acids, glutamine is the most widely represented amino acid in our body: it is found in the highest amounts in muscles and blood.
It performs a vast number of functions, including:
- maintaining the integrity of muscle tissue;
- supporting immune system function;
- transporting nitrogen to tissues;
- serving as a substrate for creating antioxidants;
- creating DNA;
- metabolism and synthesis of glucose 4.
Glutamine is synthesized directly in the muscles 5.
During certain diseases and possibly during increased physical exertion in sports and bodybuilding, the internal mechanism of its synthesis may not cope with the growing demand, which explains the reasonableness of its additional intake in some cases.
1 Glutamine for Muscle Mass Gain
Glutamine is very closely related to ensuring the functioning of muscles and the synthesis of muscle protein, from which new cells are built and existing ones are restored.
When it is sufficient in the body, favorable conditions are created for muscle growth and the protection of muscles from destruction. Its deficiency, accordingly, leads to muscle catabolism (destruction) 9-11.
It is obvious that in a state of catabolism, muscle mass will not grow.
This relationship was clearly demonstrated in experiments when glutamine was administered via injections into the muscles 10: the rate of muscle synthesis increased by 66%. This emphasizes the unique role of glutamine in muscle mass gain.
Another indirect mechanism of glutamine’s influence on muscles is that it promotes the accumulation of another important amino acid, leucine – one of the three BCAA amino acids, which play a colossal role in the processes of growth and recovery of muscle mass 6. See our material on the benefits of BCAA amino acids for muscle growth.
At the cellular level, glutamine increases muscle protein synthesis. This is confirmed when it is administered directly into the muscles.
However, the following is interesting.
Some studies aimed at determining how beneficial additional glutamine intake is for muscle mass gain demonstrate its uselessness for this purpose.
Let’s consider some of them.
Experiment: The Benefits of Glutamine for Muscle Mass Gain
The study involved 31 young individuals aged 18-24 years. Some of them took glutamine at a dose of 0.9 g/kg of muscle mass per day, while the other group took the same amount of carbohydrates (maltodextrin). The experiment lasted 6 weeks, during which all participants performed strength training of varying intensity 12.
Each time before and after training, strength indicators, changes in muscle mass, and the rate of muscle protein breakdown (through urine analysis) were assessed.
Result: the researchers found no significant difference between the two groups. Their conclusion:
“The intake of glutamine as a supplement during strength training does not affect muscle strength, muscle mass gain, or the rate of muscle cell breakdown.“
This is not the only similar experiment.
The uselessness of glutamine for muscle mass gain has also been shown in studies when taken alongside creatine 13, protein and carbohydrate shakes 14, amino acids and carbohydrates 14.
The lack of effect for muscle mass gain from glutamine consumption is also asserted by researchers at Examine.com, who study the effectiveness of various dietary supplements from a scientific data perspective 18.
Scientists’ reviews on the benefits of glutamine for muscle mass gain: “Taking glutamine as a supplement during strength training does not affect muscle mass gain, increase muscle strength, nor does it prevent the breakdown of muscle cells.”
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2 Glutamine and immunity
The main source of energy for most cells in our body is glucose. Immune cells – leukocytes – require a faster source, which is glutamine for them. Regular and sufficient intake of glutamine is important for maintaining immunity.
In a healthy body, there is enough glutamine to support immune function.
Additional intake of it as a supplement is only necessary in cases of critical illnesses or serious surgeries, when immune function is activated 8.
In this case, the intake of certain substances that strengthen immunity, above the recommended norm, can be beneficial. Among such substances, in addition to glutamine, are: arginine, omega-3, beta-carotene, BCAA amino acids.
Glutamine plays a key role in maintaining immunity. In a healthy body, it is present in sufficient quantities, and there is no need for additional intake. In the case of illnesses, the need for it sharply increases.
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3 The benefits of glutamine for weight loss
Research indicates that taking glutamine helps to “smooth out” spikes in blood glucose levels when consuming carbohydrates 7.
A sharp increase in blood glucose levels in a healthy body is accompanied by an equally sharp drop due to the increase of insulin in the blood, which functions to control glucose concentration.
Low blood glucose concentration (=energy) manifests as a strong feeling of hunger, which is well known to all sweet tooths: after consuming something sweet, one quickly feels hungry again.
Since sweets are generally loaded with calories and do not satisfy hunger, their consumption leads to excessive and unnoticed intake of surplus calories.
Accordingly, controlling blood glucose levels is one of the weight loss strategies.
This explains the benefits of low-carbohydrate diets for weight loss.
In the experiment mentioned, the properties of glutamine in controlling glucose levels are not the prerogative of this amino acid alone. This characteristic is typical for protein in general, which determines the recommendations to increase its intake during weight loss.
Glutamine may be beneficial for weight loss as it helps control blood glucose levels. This property is characteristic of protein foods in general and is not solely the merit of this amino acid.
4 Creatine and Glutamine
To understand how effective the combination of glutamine and creatine is for gaining muscle mass, let’s consider the following experiment.
Experiment: The effect of taking creatine and glutamine together
The experiment involved 29 athletes, young men and women. All participants were divided into three groups:
- one group took 0.3 g of creatine per kilogram of muscle mass per day for 1 week, followed by 0.03 g/kg of creatine for 7 weeks;
- the second group took the same dose of creatine along with glutamine at a dose of 4 grams per day;
- the third group received a placebo (“dummy”).
All participants followed the same strength training program.
Result: both groups (creatine and creatine+glutamine) showed a significant increase in muscle mass (an average of 2 kg over 8 weeks), while the placebo group showed no changes.
The addition of glutamine to creatine did not show a significant effect in muscle mass gain, reduction of body fat percentage, or improvement in strength indicators, as expected by scientists 13.
The group taking only creatine gained ~1.7 kg of muscle mass, while the creatine and glutamine group gained ~2.3 kg, which is significantly less than what scientists expected.
Scientific research indicates that the combined intake of creatine and glutamine provides a slight advantage in muscle mass gain.
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5 Muscle Strength
The intake of glutamine does not affect strength indicators 12,15, both in high doses (0.9 g/kg of body mass) and in low doses (0.3 g/kg of body mass).
Experiment: The effect of glutamine on muscle strength
In one study, 6 strength athletes (average age 21 years, weight 76 kg) took glutamine or glycine or a placebo (each athlete was randomly assigned one of the drinks) and after 1 hour performed 4 sets of exercises to muscle failure (2 sets of squats with 200% of body weight, 2 sets of bench press with 100% of body weight) 15.
Result: no significant difference in the number of repetitions was noted in any of the three groups.
Experiment: The effect of glutamine on muscle strength
In another similar experiment involving 31 young athletes (ages 18-24), researchers also demonstrated the uselessness of glutamine intake for increasing strength indicators, body fat percentage, and preventing muscle catabolism (breakdown).
All participants were randomly divided into two groups: one took glutamine at a dose of 0.9 g/kg of body mass; the other took a placebo (maltodextrin) at the same dose. The experiment lasted for 6 weeks, during which all participants trained according to the same strength training program.
Conclusion of the researchers:
“The intake of glutamine during strength training in bodybuilding has no effect on increasing muscle strength, body composition, and preventing the breakdown of muscle cells.”
Scientists’ review on the effectiveness of glutamine: “The intake of glutamine during strength training in bodybuilding has no effect on increasing muscle strength“
6 Endurance
Separate studies indicate that the consumption of glutamine by athletes has no effect on increasing endurance during intense exercise 16.
This was demonstrated in an experiment where professional athletes took glutamine at a dose of 0.03 per kg of body weight and performed 5 sets of intense exercises at maximum oxygen consumption (100% VO2).
As a result, it was shown that the intake of glutamine does not affect either the rate of “muscle acidification” or the time until fatigue occurs.
Scientists’ reviews on the effectiveness of glutamine: “The intake of glutamine does not affect either the rate of ‘muscle acidification’ or the time to fatigue during intense exercise“
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7 Protection against muscle catabolism
Additional intake of glutamine in conditions of insufficient dietary intake or protein deficiency in the body may prevent muscle catabolism: adequate levels of glutamine in the blood prevent the conversion of other essential amino acids (particularly BCAAs) important for maintaining and repairing muscle tissue into glutamine 17.
Note: this refers to cases when the diet is low in protein. This is important, as athletes typically consume protein in sufficient amounts.
The intake of glutamine in conditions of insufficient protein intake from food may prevent muscle catabolism. For athletes, whose diets generally contain elevated levels of protein, this is not relevant.
We recommend: How to take protein for muscle growth?
Which foods contain glutamine?
Glutamine is found in large quantities in animal-derived protein-rich foods: meat, eggs, and dairy products, as well as in sports nutrition derived from them (whey protein, casein, egg protein) 1:
- in beef protein – 4.7%;
- in whole milk protein – 8.1%;
- in white rice protein – 11.1%;
- in corn protein – 16.2%;
- in tofu (soy) protein – 9.1%;
- in egg protein – 4.3%.
In terms of a 100 g serving, the glutamine content in the products is as follows:
| Product | Beef | Milk | White Rice | Corn | Tofu (Soy) | Egg |
|---|---|---|---|---|---|---|
| Protein content in 100 g | 25.9 | 3.4 | 2.7 | 2.5 | 6.6 | 12.6 |
| Total amino acids mass | 25.9 | 3.4 | 2.7 | 2.5 | 6.6 | 12.6 |
| Glutamine | 1.231 | 0.275 | 0.301 | 0.406 | 0.603 | 0.559 |
Note that plant proteins contain significantly more glutamine relative to the total mass of protein.
The problem, however, is that the relevant natural plant products contain a relatively high proportion of carbohydrates (= calories) with a low relative mass of the protein itself, which in the overwhelming majority of cases is also inferior in quality to animal proteins.
The differences between plant and animal proteins are discussed in more detail in our material on natural protein-rich products.
On average, a healthy person needs about 7 g of glutamine each day.
Glutamine is found in large quantities in protein-rich animal products: meat, eggs, and dairy products
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How to take glutamine and is it worth it?
As with all amino acids, let’s start with some “moral lessons”.
Absolutely all amino acids are incredibly important in the body. This is an indisputable fact.
Many of them are directly involved in the process of building muscle mass. This is how nature intended it.
But. Understanding this does not justify arbitrary manipulations in increasing the doses of certain amino acids to enhance the expected effect in an attempt to outsmart nature.
Our recommendation: start your search for the answer to the question “how to take glutamine” (or any other amino acid) by studying our material on What is better: protein or amino acids?, where we have gathered reviews from doctors and experts on the advisability of taking amino acids in free form.
In general, scientists do not recommend taking amino acids in the form of supplements, with the exception of medical cases.
In medicine, glutamine is taken orally and in the form of injections. The usual dose is 5 g and above.
A dose of 5 g is sufficient to maintain gut health, as well as to combat the deficiency of this amino acid, which is characteristic of diets with insufficient protein (veganism, vegetarianism), as well as states of acute need for this amino acid in diseases and injuries (for example, burns).
As for athletes and bodybuilders, in particular, due to the lack of evidence of its effectiveness for gaining muscle mass and increasing endurance, discussing exact dosages is pointless.
If the arguments presented above seem unconvincing, then when calculating the dose of glutamine, it is necessary to at least consider the amount that comes from food.
In a diet with a high protein content, the use of glutamine as a supplement seems unjustified.
Doctors recommend taking glutamine as a supplement only in certain medical conditions (injuries, some diseases), for those at risk of deficiency (vegans). Athletes on a high-protein diet do not need additional glutamine intake.
We recommend: How to take BCAA amino acids and is it worth it? Maybe protein is better?
Harm of Glutamine
Overall, glutamine is considered a harmless supplement (and as you have already understood, not very useful). However, as is known, even the most beneficial and harmless product can turn into poison when consumed in excessively large doses.
The opinion of scientists on the harm of glutamine can be found in the material Harm of Glutamine and Possible Side Effects.
