Glutamine is an amino acid naturally produced by the body. Its synthesis takes place mainly in the muscles starting from three other amino acids called, respectively, arginine, ornithine and proline. In the industrial field, glutamine is obtained from protein sources of plant or animal origin Whey and gluten (protein complex contained in wheat and other cereals) are excellent sources of glutamine.
Although belonging to the category of non-essential amino acids, glutamine plays a leading biological role. Thanks to these important properties it has recently been classified as a conditionally essential amino acid. All those amino acids that play a fundamental role in maintaining body homeostasis belong to this category. In certain physiological situations, including intense physical activity, glutamine and other conditionally essential amino acids, may not be synthesized quickly enough to cope. to the real needs of the organism.
In the thriving market of food supplements, this precious amino acid is known above all for its anti-catabolic and stimulating effect on protein synthesis.
The use of glutamine supplements as an ergogenic support derives from the widespread belief that this amino acid can promote recovery and increase protein synthesis thanks to its stimulatory effect on the secretion of GH (growth hormone). These hypotheses are supported by some studies but currently, there is no definite evidence on the real ergogenic potential of this supplement.
Recent research [1] has instead shown that glutamine increases the availability of muscle glycogen during recovery. This characteristic would be the basis of what is reported by all those endurance athletes who appreciate the ergogenic virtues of glutamine-based supplements.
60% of glutamine present in the human body is contained in muscle tissue and its plasma concentrations decrease after intense and prolonged exercise.
Glutamine and immune response
One of the most important and discussed functions of glutamine is its role in maintaining normal immune function. In fact, this amino acid represents the fundamental energetic substrate for the cells responsible for the defense of the organism, in particular for the lymphocytes and macrophages.
Intense physical activity puts a strain on the athlete's immune defenses by increasing susceptibility to infections. Let's think, for example, of the cyclists engaged in a long stage race. The high physical effort, combined with the reduced percentage of fat and competition stress, makes their physique more easily attacked by infections (especially localized in the upper airways). The hypothesis that glutamine can increase the immune defenses of sporting is scientifically founded. Its effectiveness in contrasting immunosuppression is however limited to cases in which physical activity is particularly intense and protracted for long periods of time. It is difficult to think, especially in the light of what has been reported by numerous researches, that amateur or amateur sporting activity can be accompanied by immunosuppression. If anything, the opposite is true and moderate physical exercise must be seen as the ideal means to increase the effectiveness of immune system.
Whatever the sport and the level of intensity with which it is practiced, it is still important to take care of diet and food supplementation. Think for example of a malnourished man who works in the mine ten hours a day. The pickaxe blows are a good physical activity but, in this specific case, they do nothing but weaken even more an organism already tried by a diet poor in nutrients.
Additional functions of glutamine
Glutamine favors the entry into muscle cells of water, amino acids and other substances, volumizing them.
In addition to stimulating protein synthesis and hindering catabolism, this characteristic could be at the basis of the increased availability of muscle glycogen during recovery (remember in this regard that water is essential in glycogenosynthesis, in fact, for every gram of glycogen produced. , about 2.7 g of water binds to it).
As mentioned at the beginning of the article, according to some studies promptly denied by others, glutamine would naturally increase the secretion of growth hormone. To be effective in this respect, glutamine-based supplements should be taken fasting, in low conditions. blood sugar levels.
Glutamine is involved in the formation of glutathione, a powerful exogenous antioxidant consisting of glycine, cysteine and glutamic acid. Going back to what has been said about the immune response, we remember that "physical activity increases the production of free radicals. On the other hand, if supported by the right recovery times and adequate nutrition, it improves the endogenous antioxidant systems, including that mediated by glutathione. peroxidase (GPX).
Glutamine is also involved in overtraining syndrome; there is in fact a relationship between the permanent drop in plasma levels of gultamine and the appearance of symptoms typical of overtraining (chronic fatigue, weight loss, loss of appetite, the appearance of minor infections, nausea, depression, apathy, increased heart rate at rest and decreased training heart rate). According to some researchers, the administration of gultamine and branched-chain amino acids would therefore be useful in periods of intense training to strengthen the immune system and reduce the risk of overtraining.
Intake of glutamine
According to the desired effects, the intake of glutamine:
- it must take place one "hour before" the start of the effort together with carbohydrates as, in addition to being better absorbed in conditions of high blood sugar, glutamine promotes optimal sports performance
- must take place immediately after training, within thirty minutes from the end of the exercise. In this case, supplementation is recommended together with abundant fluids and branched amino acids. This intake protocol is the best way to promote recovery and cellular anabolic processes.
- it must take place on an empty stomach, possibly before going to bed, to stimulate the secretion of GH
The recommended intake dose is around 1-1.5 grams of glutamine per day. However, it should be emphasized that in many studies that attest to its ergogenic properties, much higher dosages have been used (5 grams or 0.1 g per kg of body weight). The intake of glutamine should however vary in relation to physical effort and diet. The need for glutamine increases dramatically in the case of a diet low in protein foods and when workouts are particularly intense and long-lasting.
Like all protein or amino acid supplements, glutamine is contraindicated for people with kidney disorders. Its use is not recommended even during pregnancy and under the age of 12. These directives have been established by the Ministry of Health and must be compulsorily reported on the label.
[1] (Vamier, M., et al: Stimulatory effect of glutamine on glycogen accumulation in human skeletal muscle. Amer. J. Physiol., 269: E309, 1995).
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