Truths and myths about one of the most popular amino acids
Glutamine is the most common amino acid in the body and, as such, is rarely sufficient. The vast number of processes in which it is involved often confuses the body to compromise on where to take glutamine for one or another metabolic pathway.
What is glutamine?
L-glutamine, or glutamine, is a non-essential amino acid because it is synthesized from various organs of the body - the volitional muscles, the liver, etc. It is the amino acid that occurs most in the plasma of the blood - 30-35% and contains about 20% of hydrogen in its structure, making it the main hydrogen carrier for muscle cells.
Glutamine is mainly concentrated in the muscles of the human body, thanks to the activity of the enzyme glutamine synthetase.
How is it produced?
Typically, glutamine is produced biotechnologically by fermentation of a suitable culture medium by bacteria.
What is the main physiological effect of glutamine?
Glutamine is a conditionally essential amino acid, because its body needs increase in certain conditions such as sickness or cachexia.
The main role of glutamine is:
To serve as a hydrogen transport between tissues and alanine;
To be a precursor to the antioxidant glutathione;
To be a precursor to nucleotides;
To regulate acid and base metabolism;
To participate in glycogenogenesis;
To stimulate the production of citrulline and glycine.
Why and how do we accept it?
Research shows that after heavy workout, the glutamine level in the body drops to 50%. Therefore, it is best to take it after a workout. It also helps to restore muscle glycogen (easily converting to glucose without raising blood sugar and insulin levels), strengthens protein synthesis and increases the levels of some important hormones that cause muscle growth. For fitness sports, the best option is to take about 30 minutes after a workout.
What are the additional physiological effects of glutamine?
In the brain, it is the source of building glutamate by "robbing" excess ammonia. Glutamine is also an ingredient of glutathione - the most powerful antioxidant in our body.
Thirteen percent of circulating glutamine is stored in some internal organs, such as the liver and intestinal enterocytes, where they serve as a source of energy.
Proven and potential human benefits
It has a mixed effect on the levels of ammonia in the body. Taking recommended doses leads to a reduction in ammonia, while glutamine overdoses leads to a significant increase, which is more pronounced in the elderly;
It significantly increases blood sugar and consequently insulin levels due to the direct conversion of glutamine into glucose. This may not be recommended for people with high blood sugar, but has the potential to fuel in sports;
Increases aerobic capacity at exercise, but only in individuals with angina. In individuals with cardiac abnormalities, no effect is noted;
Potential benefits for treating bowel disease, inflammation and digestion. For now, there is limited evidence that oral intake of glutamine may help with Crohn's disease or other inflammatory processes in the digestive tract. Glutamine also strengthens protein synthesis in the intestines themselves;
Oral intake of glutamine significantly improves cardiac abnormalities in subjects undergoing cardiac surgery. In other cases, there is no significant effect;
Despite the long-standing claims that glutamine helps increase muscle mass, the amino acid does not have a similar effect when taken by mouth because a small portion reaches the blood. This is not the case with an injection. The direct introduction of glutamine into serum significantly increases the protein synthesis in the muscles;
Potential benefits to increase endurance. This effect is based on two mechanisms. The first is the conversion of glutamine into glucose, which is used as fuel by the body. The second mechanism is related to the reduction of ammonia levels, which improves cardiovascular activity;
Injecting glutamine significantly helps to reduce muscle catabolism.
Proven and potential benefits in animals and in vitrо
Significantly improves the conditions of damage to heart cells in ischemia and other heart diseases;
Increases muscle protein synthesis in in vitro tests or by intake directly into the blood.
What are the optimal doses?
The optimal glutamine dose is considered to be 0.2 g per kilogram of weight (eg for an 80 kg person - 16 g). Doses of up to 0.3 g per kg of weight were tested to be harmless. Even for short-term intake, 0.5 g per kg of weight is given without any side effects. A dose of 2 g taken half an hour after workout causes a marked increase in growth hormone and slightly less - insulin and testosterone (observed 2 hours after dosing). A dose of 4 g causes an even greater increase. Some studies suggest that growth hormone may increase up to 4 times at this dose.
What are the possible harmful / side effects when taking it?
Glutamine has no side effects, but if too high doses are used, it is possible to have a stomach upset. If this happens, wait until it goes away and then take smaller doses.
Studies have found that the upper limit is 0.75 g per kg of body weight, which for one 80 kg male means 60 g of glutamine daily dose. It is unclear what the long-term effect of such high doses will be. It is possible that glutamine will lead to an increase in ammonia, as well as urea and creatinine, especially in the elderly.
How is glutamine digested by the body?
After ingestion through the digestive system, glutamine is rapidly metabolised to citrulline, arginine, glutamate and proline.
Glutamine is not known for its high absorption, and a small portion of it reaches the serum. One study found that free form glutamine had the same bioactivity as protein-bound glutamine in food sources. However, food is preferred as the source of the amino acid.
The only case in which glutamine is found to be a food supplement increases serum glutamine levels in people suffering from permanent angina.
What are the foods that contain the highest amount of glutamine? It is contained in protein-rich foods such as legumes, meat, fish and dairy products.
The richest source of glutamine is veal containing between 4.4 and 4.8%, pasteurized milk with 8.7% -9.2%, white rice with 11.1%, maize with 16.2% and eggs with 4.3%.
Which are the main source of glutamine?
Glutamine is contained in many preparations, in the form of tablets, in powder or liquid form. It also participates in preparations that contain a combination of amino acids in all protein concentrates, and can also be found as a separate preparation, most commonly available in the form of unsweetened powder.
Glutamine is also present in some complex products, but is in a lower amount. Besides glutamine, they also contain other amino acids, L-carnitine and creatine. Products with added glutamine are some of the most well-known amino acid formulas such as Scivation Xtend and BCAA Blast.
Glutamine-containing preparations are for oral use and are available in powder, liquid or tablet form.
What can we combine glutamine?
There is no scientific basis on which to make recommendations for combining glutamine with other products.
The practice has found that for sports purposes glutamine can be added to products like creatine, protein and BCAA.
For treatment of digestive tract health, glutamine can be combined with probiotics and fiber.