Glutamine: One of the Most Important Amino Acids

Posted On September 5, 2017 at 12:22 pm by / No Comments

Glutamine: One of the Most Important Amino Acids

 Glutamine: One of the Most Important Amino Acids

What is glutamine?
Glutamine has a simple beginning. In 1883, researchers discovered its structure from two unlikely sources—beet juice and wheat.(3) Once identified, scientists thought that humans did not have to have it in the diet because the body could make it. However, scientists quickly updated this idea once they realized that the body could not make enough glutamine during certain kinds of stress and now they refer to glutamine as semi-essential or essential under certain conditions.(4)

Glutamine is one of twenty amino acids or building blocks that are responsible for making hair, skin, nails, organs, hormones and many other parts of the body. It is the most abundant amino acid in the body and makes up a little more than half of the free amino acids in the muscles and blood. It is made and stored in the skeletal muscle and is synthesized from glutamate and ammonia.

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Glutamine’s
role in
the body

Glutamine has a laundry list of functions in the body and impacts the body in several ways. For example, glutamine is a substrate for protein, neurotransmitter and nucleic acid synthesis and, it is a precursor for the production of the antioxidant, glutathione. Among these and other functions of glutamine, there are several that are of great interest. Take a look at what glutamine can do for the body.

Glutamine & detoxification

Glutamine has two nitrogen atoms in the form of an alpha-amino group and an amide group. Because of these two nitrogen groups, glutamine is able to shuttle nitrogen back and forth throughout the body. It is estimated that one-third of all amino-acid nitrogen is transported by the blood in the form of glutamine.

The liver and kidneys play key roles in managing this nitrogen-containing compound. The liver is able to detoxify the blood by removing excess ammonia from venous blood and converting it to glutamine to keep the blood from becoming toxic. On the other hand, the kidneys are able to make ammonia from glutamine and excrete it as necessary. These functions show the importance of glutamine in the body, and that it helps regulate the acid/base balance and keep blood healthy. (5,6)

Glutamine
&
Exercise

Glutamine & Exercise

Scientists and others debate about the role of glutamine and exercise. Researchers initially speculated that glutamine was the antidote for almost every problem that ailed exercisers and athletes. However, the dust has settled somewhat and there are a few facts we know about exercise and glutamine.

Researchers report that prolonged exercise may contribute to excess ammonia. In a double-blind study, researchers examined the idea that excess ammonia may cause fatigue. Researchers identified 15 men who could run long distance. These men ran outdoors for 120 minutes on 4 different occasions. During the first run, the men did not take any supplements (control). Before the second run, the men took carbohydrates as a bolus. During the third run, they consumed glutamine. And on the final run, the men had a combination of carbohydrates and glutamine. Researchers drew blood every 30 minutes during each run and kept track of ammonia levels. During the control run, they noticed that the ammonia levels increased to about 70% above the initial levels. When the men received glutamine and carbohydrates, the ammonia levels stayed the same as the control for the first 60 minutes but during the second 60 minutes, ammonia levels dropped lower than the first run or the control run. Because of this study, researchers believe that glutamine with carbohydrates may reduce ammonia levels. Perhaps this mechanism can also reduce fatigue.(7)

In another study, researchers examined glutamine’s effect on ammonia during exercise among football players. The players were divided into two groups. One group received glutamine and the other group was given alanine supplementation before exercise. The players were given two exercise protocols—one with intervals and the other with continuous exercise. Researchers reported that blood levels of ammonia increased during both exercises. In either case, glutamine was shown to protect against high levels of ammonia during exercise.(8)

Researchers have conducted preliminary studies to understand the effect of glutamine on glucose levels. In an animal study, researchers measured glutamine’s effect on glucose homeostasis. They found that during the post exercise period, glutamine was able to help maintain glucose levels. This in turn, helps to maintain energy levels and reduce fatigue.(9)

Glutamine & the Immune System

Glutamine
& the
Immune System

Glutamine is intricately involved in the immune system. It is needed to synthesize nucleotides and this is important for rapid cell division within the immune system and the gastrointestinal system. Low levels of glutamine can compromise these systems. Researchers have shown that supplementing with glutamine during these states can speed up recovery time, and reduce morbidity and mortality. Researchers have also pointed out that glutamine supplementation has also reduced hospital stay among those with infectious complications.(10, 11, 12, 13)

Glutamine is also thought to increase interleukin-6 (IL-6) activity. This compound increases the production of antibodies. When glutamine levels decrease, researchers report that it may reduce IL-6 production. One study reports that eight healthy men ingested either glutamine, glutamine-rich protein or a placebo at intervals during and two hours after cycling. Plasma IL-6 increased 11-fold with exercise but those who consumed glutamine experienced an 18-fold increase. (14)

Clinical studies have shown that patients have benefited from glutamine during severe catabolic illnesses such as burns, bone marrow transplantation, and infection; intestinal dysfunction such as inflammatory disease, short-bowel syndrome and surgical gastrointestinal patients; immunodeficiency syndromes such as HIV/AIDS; and advanced malignant disease such as muscle wasting in cancer and among low birth weight babies. (15)

When the body undergoes stress from these conditions and others, hormones such as cortisol are released in the blood. High levels of cortisol deplete glutamine. In addition, these conditions increase the demand for glutamine and can exceed the body’s ability to produce it. Supplementation of glutamine in these conditions have been shown to shorten recovery time.(16)

Researchers report that prolonged exercise or heavy training is associated with lowered glutamine levels. These reduced levels seem to be associated with increased respiratory infections, especially among long distance runners. Supplementing with glutamine increases glutamine levels but more research needs to be done to better understand this mechanism.(17)

Glutamine
&
Growth Hormone

Glutamine & Growth Hormone

Human growth hormone is known to stimulate growth and cell production and glutamine may increase circulating growth hormone. Researchers gave nine subjects two grams of glutamine in a cola drink 45 minutes after a light breakfast. The subjects ingested this over 20 minutes. Forearm venous blood was drawn at zero time and at 30-minute intervals for 90 minutes. Eight of the subjects experienced an increase at 30 and 60 minutes but levels returned to pre-testing levels at 90 minutes. This study shows that glutamine can increase growth hormone levels. In this study, researchers mentioned that two grams of glutamine is the ideal amount to give to the body. This is because it does not trigger hepatic conversion of glutamine or cause the body to convert glutamine to ammonia.

Another study administered 20 times this amount of glutamine and provoked hepatic glutamine removal. Researchers also commented that less than one gram would not have had any benefit. (18)

Glutamine & Muscle Growth

In catabolic states, glutamine has been shown to increase protein synthesis.(19) It has been theorized that increasing glutamine levels increase protein metabolism. This may result in skeletal muscle growth. Researchers tested this theory in mice and reported that glutamine did indeed increase skeletal muscle growth. Other studies are needed to confirm this theory in humans.(20)

Glutamine & Cravings

Glutamine
&
Cravings

Research is scarce when it comes to glutamine’s role in reducing sugar and alcohol cravings. However, one study mentions that within the brain, glutamatergic neurotransmission following alcohol withdrawal can increase cravings.(21) Glutamine is recommended by the University of Maryland Medical Center as a substance that doctors may recommend to help reduce cravings.(22)

Wrapping it up

Glutamine is a major amino acid in the body and it has many valuable functions. Glutamine helps maintain the nitrogen balance in the bloodstream. It may benefit exercisers by reducing ammonia levels and maintain glucose levels. This may reduce fatigue. Glutamine may boost IL-6 activity which, in turn, helps boost the immune system. It also has been shown to reduce healing time during heavy stress. Glutamine also increases protein synthesis, raises growth hormone levels in the body and may cut cravings.

These functions of glutamine clearly establish this amino acid as the crowning jewel of amino acids. In general, glutamine provides benefits for athletes and it can help you stay at the top of your game of good health. Its future holds promise to do even more as researchers continue to uncover its role.

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References

  1. Whitney EN, Cataldo CB and Rolfes SR. (2002). Understanding Normal and Clinical Nutrition. 6th ed. United States of America: Wadswoth Group. 734.
  2. Abcouwer S. and Souba W. (1999). Glutamine and Arginine. In: Shils M, Olson J, Shike M, and Ross A. Modern Nutrition in Health and Disease. 9th ed. Baltimore, MD: Williams & Wilkins: A Waverly Company. 559 – 569.
  3. Waddell D and Fredricks K. Effects of a glutamine supplement on the skeletal muscle contractile force of mice. American Journal of Undergraduate Research. 2005;4(2):11-17.
  4. Iwashita S, Williams P, Jabbour K, et al. (2005). Impact of glutamine supplementation on glucose homeostasis during and after exercise. J Appl Physiol. 99, 1858-1865.
    Abstract
  5. Abcouwer S. and Souba W. (1999). Glutamine and Arginine. In: Shils M, Olson J, Shike M, and Ross A. Modern Nutrition in Health and Disease. 9th ed. Baltimore, MD: Williams & Wilkins: A Waverly Company. 559 – 569.
  6. Haberle J, Gorg B, Rutsch F, et al.. (2005). Congenital glutamine deficiency with glutamine synthetase mutations. N Engl J Med. 353 (18), 1926-1933.
    Abstract
  7. Carvalho-Peixoto J, Alves RC, and Cameron LC. (2007). glutamine and carbohydrate supplements reduce ammonemia increase during endurance field exercise. Appl Physiol Nutr Metab. 32 (6), 1186-1190.
  8. Bassini-Cameron A, Monteiro A, Gomes A, et al. . (2007). Glutamine protects against increases in blood ammonia in football players in an exercise intesity-dependent way. British Journal of Sports Medicine. 42, 260-266.
    Abstract
  9. Iwashita S, Williams P, Jabbour K, et al. (2005). Impact of glutamine supplementation on glucose homeostasis during and after exercise. J Appl Physiol. 99, 1858-1865.
    Abstract
  10. Castell LM. (2002). Can glutamine modify the apparent immunodepression observed after prolonged, exhaustive exercise? Nutrition. 18 (5), 371-375.
    Abstract
  11. Melis GC, ter Wengel N, Boelens PG, et al. (2004). Glutamine: recent developments in research on the clinical significance of glutamine. Curr Opin Clin Nutr Metab Care. 7 (1), 59-70. Abstract
  12. Klimberg VS. (2005). Is glutamine effective in enhancing host immune response to tumors? J Nutr. 135, 2929S.
  13. Wischmeyer PE. (2008). Glutamine: role in critical illness and ongoing clinical trials. Curr Opin Gastroenterol. 24 (2), 190-197.
    Abstract
  14. Hiscock N, Petersen EW, Krzywkowski K, et al. (2003). Glutamine supplementation further enhances exercise-induced plasma IL-6. J Appl Physiol. 95, 145-148.
    Abstract
  15. D’Souza R, and Powell-Tuck J. (2004). Glutamine supplements in the critically ill. J R Soc Med. 97, 425-427.
    Abstract
  16. Griffiths RD. (2001). The evidence for glutamine use in the critically-ill. Proceedings of the Nutrition Society. 60, 403-410.
    Abstract
  17. Gleeson M. (2008). Dosing and efficacy of glutamine supplementation in human exercise and sport training. J Nutr. 138, 2045S-2049S.
    Abstract
  18. Welbourne TC. (1995). Increased plasma bicarbonate and groth hormone after an oral glutamine load. Am J Clin Nutr. 61, 1058-1061.
    Abstract
  19. Rutten E, Engelen M, Wouters E, et al.. (2006). Metabolic effects of glutamine and glutamate ingestion in healthy subjects and in persons with chronic obstructive pulmonary disease. Am J Clin Nutr. 83 (1), 115-123.
    Abstract
  20. Waddell D, and Fredricks K. . (2005). Effects of a glutamine supplement on the skeletal muscle contractile force of mice. American Journal of Undergraduate Research. 4 (2), 11-17.
  21. Javier J and Hidalgo M. . (2006). Withdrawal from free-choice ethanol consumption results in increased packing density of glutamine synthetase-immunoreactive astrocytes in the prelimbic cortex of alcohol-preferring rats. Alcohol and Alcoholism. 10, 1-7.

University of Maryland Medical Center.  (2007). Alcoholism. Available: http://www.umm.edu/altmed/articles/alcoholism-000002.htm. Last accessed 03/29/09.
Abstract

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