Glutamine King of Amino acids? Health Benefits, Uses, Side Effects Most Popular

Glutamine health benefits Truths and myths about one of the most popular amino acids

Glutamine is the most abundant amino acid in the body and as such is rarely sufficient. The huge number of processes in which it is involved, often confronts the body where to get glutamine for one or another metabolic pathway.

What is glutamine?

L-glutamine, or glutamine for short, is a non-essential amino acid, as it is synthesized by various organs of the body – the volitional muscles, liver and others. It is the amino acid that is found in the largest amount in blood plasma – 30-35% and contains about 20% hydrogen in its structure, which makes it the main carrier of hydrogen for muscle cells. Glutamine is concentrated mainly in the muscles of the human body, thanks to the activity of the enzyme glutamine synthetase.

How is it produced?

Glutamine is usually produced biotechnologically by fermentation of a suitable nutrient medium from bacteria.

What is the main physiological effect of glutamine?

Glutamine is a conditionally essential amino acid because the body’s needs for it increase in certain conditions such as disease or cachexia. The main role of glutamine is:

  • To serve as a hydrogen transporter between tissues together with alanine;
  • To be a precursor of the antioxidant glutathione;
  • To be a precursor of nucleotides;
  • To regulate acid and basal metabolism;
  • To participate in glycogenogenesis;
  • To stimulate the production of citrulline and glycine.

Why and how to accept it?

Studies show that after a hard workout, the level of glutamine in the body drops to 50%. Therefore, it is best taken after a workout. It also helps restore muscle glycogen (easily converted to glucose without raising blood sugar and insulin levels), boosts protein synthesis and increases levels of some important hormones that cause muscle growth. For fitness athletes, the best option is to take it about 30 minutes after a workout.

What are the additional physiological effects of glutamine?

In the brain, it is a source for the construction of glutamate by “robbing” excess ammonia. Glutamine is also a component 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 benefits in humans – Glutamine health benefits

  • It affects the levels of ammonia in the body in different ways. Taking the recommended doses leads to a decrease in ammonia, while an overdose of glutamine leads to a significant increase, which is more pronounced in the elderly;
  • Significantly increases blood sugar and subsequently insulin levels due to the direct conversion of glutamine to glucose. This may not be recommended for people with high blood sugar, but it has fuel potential in athletes;
  • Increases aerobic capacity during exercise, but only in people with angina. In individuals with cardiac abnormalities, no effect was noted;
  • Potential benefits for the treatment of intestinal diseases, inflammation and improved digestion. There is currently limited evidence that oral glutamine can help with Crohn’s disease or other inflammatory processes in the digestive tract. Glutamine also enhances protein synthesis in the gut itself;

  • Oral glutamine significantly improves heart abnormalities in people who have undergone heart surgery. In other cases, no significant effect is observed;

  • Despite long-standing claims that glutamine helps increase muscle mass, the amino acid has no similar effect when taken orally because a small portion reaches the bloodstream. This is not the case with injection. Direct injection of glutamine into the serum significantly increases proein synthesis in the muscles;
  • Potential benefits for increasing endurance. This effect is based on two mechanisms. The first is the conversion of glutamine to 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 vitro

  • Significantly improves the state of damage to heart cells in ischemia and other heart diseases;
  • Increases muscle protein synthesis in in vitro tests or by injection directly into the blood.

What are the optimal doses?

It is estimated that the optimal dose of glutamine is 0.2 g per kilogram of body weight (eg for an 80-kilogram person – 16 g). Doses up to 0.3 g per kg body weight have been shown to be harmless. Even for short-term use, 0.5 g per kg of body weight was given, without taking into account side effects. A dose of 2 g taken half an hour after a workout causes a significant increase in growth hormone and a slightly lower increase in insulin and testosterone (observed 2 hours after ingestion). A dose of 4 g causes an even greater increase. According to some studies, growth hormone can be increased up to 4 times at this dose.

What are the possible harmful / side effects when taking it?

Glutamine has no side effects, but if excessive doses are used, an upset stomach is possible. If this happens, wait until it passes and then take smaller doses. Studies have found that the upper limit is 0.75 g per kg of body weight, which for an 80 kg man means 60 g of glutamine daily dose. It is not clear what the long-term effect of such high doses will be. Glutamine may increase ammonia, as well as urea and creatinine, especially in the elderly.

How is glutamine absorbed by the body?

After ingestion, glutamine is rapidly metabolised to citrulline, arginine, glutamate and proline. Glutamine is not known for its high digestibility and a small part of it reaches the serum. One study found that glutamine in free form had the same bioactivity as protein-bound glutamine in food sources. However, food is preferred as a source of the amino acid. The only case in which glutamine as a dietary supplement has been found to increase serum glutamine levels is in people with persistent angina.

Which foods contain the most glutamine? It is found in protein-rich foods such as legumes, meat, fish and dairy products. The richest source of glutamine is beef with a content between 4.4 and 4.8%, pasteurized milk with 8.7% -9.2%, white rice with 11.1%, corn with 16.2% and eggs with 4.3%.

What are the drugs that are a major source of glutamine? Glutamine is contained in many preparations, in the form of tablets, in powder or liquid form. It is also involved in preparations that contain a combination of amino acids in all protein concentrates, and can also be found as a separate preparation, most often offered in the form of unflavored powder. Glutamine is also found in some complex products, but in lower amounts. In addition to glutamine, they contain other amino acids, L-carnitine and creatine. Glutamine-added products are some of the most well-known amino acid formulas such as Scivation Xtend and BCAA Blast.

Preparations containing glutamine are for oral use and are available in powder, liquid or tablet form.

What can we combine glutamine with?

There is no scientific basis on which to make recommendations for combining glutamine with other products. Practice has shown that for sports purposes, glutamine can be added to products such as creatine, protein and BCAAs. To treat digestive health, glutamine can be combined with probiotics and fiber.

Glutamine health benefits

Sources used for glutamine health benefits :

  1. Garlick PJ. Assessment of the safety of glutamine and other amino acids. J Nutr. (2001)
  2. Roth E. Nonnutritive effects of glutamine. J Nutr. (2008)
  3. Galera SC, et al. The safety of oral use of L-glutamine in middle-aged and elderly individuals. Nutrition. (2010)
  4. Boza JJ, et al. Free and protein-bound glutamine have identical splanchnic extraction in healthy human volunteers. Am J Physiol Gastrointest Liver Physiol. (2001)
  5. Khogali SE, et al. Is glutamine beneficial in ischemic heart disease. Nutrition. (2002)
  6. Lenders CM, et al. Evaluation of a novel food composition database that includes glutamine and other amino acids derived from gene sequencing data. Eur J Clin Nutr. (2009)
  7. Lacey JM, Wilmore DW. Is glutamine a conditionally essential amino acid. Nutr Rev. (1990)
  8. Is Glutamine a Conditionally Essential Amino Acid?.
  9. Gleeson M. Dosing and efficacy of glutamine supplementation in human exercise and sport training. J Nutr. (2008)
  10.  Fujita T, Yanaga K. Association between glutamine extraction and release of citrulline and glycine by the human small intestine. Life Sci. (2007)
  11.  Lightfoot A, McArdle A, Griffiths RD. Muscle in defense. Crit Care Med. (2009)
  12.  Souba WW. Glutamine: a key substrate for the splanchnic bed. Annu Rev Nutr. (1991)
  13.  Glutamine and carbohydrate supplements reduce ammonemia increase during endurance field exercise. Carvalho-Peixoto J1, Alves RCCameron LC.
  14.  Oral glutamine supplementation during preoperative radiochemotherapy in patients with rectal cancer: a randomised double blinded, placebo controlled pilot study. Rotovnik Kozjek N1, Kompan LSoeters POblak IMlakar Mastnak DMožina BZadnik VAnderluh FVelenik V.
  15.  No effect of glutamine ingestion on indices of oxidative metabolism in stable COPD. Marwood S1, Jack SPatel MWalker PBowtell JCalverley P.
  16.  Glutamine and whey protein improve intestinal permeability and morphology in patients with Crohn’s disease: a randomized controlled trial. Benjamin J1, Makharia GAhuja VAnand Rajan KDKalaivani MGupta SDJoshi YK.

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