Glutamine is a nonessential amino acid. Normally the body can produce enough glutamine to meet the physiological demands placed on it. However, during times of stress the body cannot produce enough glutamine and it becomes the most important amino acid and extremely essential. Times of metabolic stress when glutamine becomes an essential amino acid include; trauma, surgery, cancer, sepsis, burns, serious injury, and intense exercise (1). Glutamine is the most abundant amino acid in our body and is used by every cell, some more then others. It is mainly synthesized and stored in skeletal muscles compromising 60 percent of the body's total glutamine stores. Glutamine is also found in significant amounts in the liver, brain, and stomach (2).
The average individual receives about five to ten grams of glutamine per day in their diet. Meats, fish, poultry, beans, protein powders, and diary products all contain glutamine. Normally dietary intake and the body's production supply adequate amounts on glutamine. During times of metabolic stress however glutamine levels can drop over 50 percent in cells and 30 percent in the plasma (3). Glutamine has recently received much scientific interest and is gaining popularity. Glutamine supplementation had been shown to benefit those with gastrointestinal problems, serious injury or illness, heart disease, and cancer. It has been shown to strengthen the immune system, increase muscle mass, and reduce symptoms of overtraining in athletes (2).
Glutamine accounts for 30-35 percent of amino acid nitrogen in the plasma (4). Sir Hans Krebs in 1935 discovered the metabolic foundation of glutamine, glutamine is synthesized from glutamate, and its vital role in tissue metabolism (5). Glutamine contains two ammonia groups; one coming from the precursor molecule glutamate, and another ammonia group comes from free ammonia in the bloodstream. These two ammonia groups contribute to glutamine's role in the body as a nitrogen shuttle, to help prevent toxic levels of ammonia from building up in the body. Glutamine acts as a buffer and is able to accept and donate nitrogen, transferring it around the body and aiding in the synthesis of many compounds like amino acids, purines, and pyrimidines. By donating nitrogen glutamine helps to build proteins, hence develop more muscle and repair muscles (4).
During intense exercise glutamine levels drop significantly, as much as 50%. This can be detrimental to athletes because the body relies on glutamine as cellular fuel. When glutamine levels are low other organs rob the skeletal muscles of glutamine. This can lead to muscle deterioration. Glutamine supplementation has been shown to minimize muscle breakdown and improve protein metabolism. A higher concentration of glutamine in the body attenuates the demand for free glutamine from other cells and tissue; immune and small intestines (6). In a study performed in 1996, subjects that received glutamine supplementation had a lower breakdown in muscle protein (7). A more recent study showed that glutamine is anticatabolic, helping to preserve muscle and prevent muscle breakdown (8, 9). Glutamine is sometimes referred to as "muscle food" and is very popular among weight lifters and body builders (2).
In addition to supplying the muscles with energy, glutamine is also the primary energy source for various cells of the immune system such as T cells, lymphocytes, and macrophages. Strenuous exercise, stress, trauma, fasting, and infections all cause depletion of glutamine concentrations in immune cells, suppressing the immune system (10). For example a study showed that strenuous exercise depleted glutamine levels by 35-50 percent and increased the incidence of upper respiratory infections (11).
Overtraining in athletes has also been linked to lower plasma glutamine concentrations when compared to athletes that were properly trained. Overtraining occurs as a result of increased intensity, volume, or frequency of workouts while failing to give the body adequate rest. This causes decreased performance, fatigue, depression, and nausea in the athlete (12). Intense training and over training may compromise the immune system by increasing susceptibility to viral and bacteria infections. Low glutamine levels lower the production of T cells and reduce the ability of macrophages to combat viruses and bacteria that may enter the body. The common cold, flu, and HIV have all been linked to lower glutamine levels (13). Oxford University performed a study on over 150 marathon runners in 1996. Half of the subjects received five grams of glutamine after a strenuous run and the other half received a placebo. Subjects that received the placebo were twice as likely to get sick following a marathon run (12). Any athlete engaging in intense, strenuous activity would benefit from supplementing with glutamine solely for its immune system properties allowing them to stay healthy and hence train more frequency.
Glutamine has also been show to benefit people recovering from a critical illness, injury, or surgery. Healing time following an operation may be reduced and hospital stay after surgery shorted. In one double blind study on seriously ill hospitalized people, half were given glutamine in the feeding tube while the other half did not receive anything additional. The group that received supplemental glutamine left the intensive care ward and hospital sooner then the control group. Glutamine supplementation also improved nitrogen balances and intestinal permeability in these people with no additional side effects (14).
The cells of the intestine, like the muscle and immune cells use glutamine as a fuel source. Supplementation has been used in people with digestive system conditions and may reduce diarrhea, digestive distress, and symptoms of inflammatory bowel disease. Alleviation of these symptoms is attributed to glutamine's ability to reduce leakage through the intestinal wall (15). Significant evidence supports glutamine's effects in the intestines: aiding maintenance of gut barrier function, reducing septic morbidity, and intestinal cell proliferation and differentiation. Supplementation could potentially benefit any individual experiencing gastrointestinal problems and reduce side effects experienced with protease inhibitors and cancer chemotherapy drugs (16).
Glutamine supplementation has also been attributed to being beneficial for many other diseases and conditions such as; cancer chemotherapy, HIV support, angina, Crohn's Disease, liver disease, hypoglycemia, and even alcoholism. Also noted was glutamine's possible link to improving brain function, glucose regulation, and glycogen formation. Speculations of future glutamine use are to possibly be used for treating insomnia, weight loss, depression, anxiety, and schizophrenia. These accusations however have little if any scientific research to back them up. Much more future research is needed to determine whether glutamine has even more benefits then we now know (2).
Glutamine is a naturally occurring amino acid and is completely safe. It has very few side effects, such as headache or upset stomach, and these are usually associated with high doses exceeding 21 grams. Constipation and bloating were even rarer. No toxic reactions were reported at doses even greater then 21 grams (17). Even though proven safe, glutamine should be used only under a doctor's discretion in diabetics, cancer patients, pregnant and nursing mothers, and those with advanced liver disease, stroke, or epilepsy (2). Those taking seizure medications should avoid taking glutamine because of a possibly antagonistic interaction.
Glutamine is available in tablets, capsules, and powder form. It is also available in enteral and parenteral nutrition and in some medical foods. Typical doses range from 4 to 21 grams and usually divided up throughout the day. Athletes would take five grams after a workout for maximum benefits (4). Glutamine can be used by strength training and high intensity athletes to prevent muscle break down and reduce sickness, those that are recovering from surgery or a trauma to reduce hospital stay, and people with gastrointestinal symptoms. Glutamine is readily available at any health and nutrition store and is one of few proven safe supplements with no side effects.
I started taking glutamine supplements about a year ago when a personal trainer at my gym informed me about it. Because it is safe and there were no side effects I decided to try it. Being a swimmer I took it for the athletic benefits including; reduced muscle deterioration, reduction in overtraining syndrome, and to keep my immune system healthy so I would not get sick as often. I guess as in most of these supplements there is no sure way to tell whether the supplement is actually working and I believe that a lot of it is psychological. Although I have noticed to some extant that when I supplement with 5 grams of glutamine after I lift weights I am usually not as sore the next day. I still take it today now more for weightlifting and muscle building because there is so much convincing evidence that it works! I never knew that it had so many other benefits as well; such as aiding in gastrointestinal problems, helping victims of traumatic injuries, and its effects in cancer patients. The gastrointestinal benefits are particularly interesting to me because I have stomach problems. So now even when I am not working out as much I will continue to supplement with glutamine for its additional benefits.
I chose to do my research paper on glutamine because I wanted to study something I was taking and see if it was something I should continue taking or stop wasting my money on. Especially after learning in this class that most supplements are not proven effective and may actually be dangerous for me I wanted to be sure glutamine was safe. I think I would recommend glutamine to any athlete for its immune system boost and its ability to reduce the effects of overtraining. I especially think body builders should supplement with it because it can help prevent muscle breakdown since body builders work so hard to increase muscle mass. Also I would recommend glutamine pretty much to anyone experiencing gastrointestinal problems or anyone recovering from surgery or other significant injury. Glutamine is one of the few supplements that is safe and has significant scientific evidence supporting its effectiveness.
Lacey, J. M., Wilmore, D. W. Is glutamine a conditionally essential amine acid? Nutritional review. 1990; 48:297-309.
Greenwell, Ivy. Glutamine: the essential "non-essential" amino acid. LE Magazine. 1999.
Souba, W. W. Glutamine physiology, biochemistry, and nutrition in critical illness. Austin, TX: R.G. Landes Co.; 1992.
Miller, A. L. Therapeutic considerations of L-glutamine: a review of literature. http://www.thorne.com/altmedrev/fulltext/glutamine4-4.html.
Krebs, H. A. Metabolism of amino-acids: The synthesis of glutamine from glutamic acid and ammonia, and the enzymic hydrolysis of glutamine in animal tissues. Biochemistry Journal. 1935 Aug; 29(8):1951-1969.
Antonio, J., Street, C. Glutamine: a potentially useful supplement for athletes. Canadian journal of applied physiology. 1999; 24(1): 1-14.
Hankard, R. G., Haymond, M.W., Darmaun, D. Effects of glutamine on leucine metabolism in humans. American Journal of physiology. 1996; 271(4): 748-754.
Hickson, R. C. Czerwinski, S. M. Glutamine prevents down regulation of myosin heavy chain synthesis and muscle atrophy. American journal of physiology. 1995; 268(4): 730-734.
Boelens, P. G., Nijveldt, R. J., Houdijik, A., Meijer, S., Van Leeuwen, P. Glutamine alimentation in catabolic state. Journal of nutrition. 2001; 131(95): 2569-2578.
Newsholme, E. A. Biochemical mechanisms to explain immuno-suppression in well-trained and over trained athletes. International journal of sports medicine. 1994; 15: 142-147.
Roth, E., et al. Metabolic disorders in severe abdominal sepsis, glutamine deficiency in skeletal muscle. Clinical nutrition. 1982; 1: 25-41.
Castell, L. M., Poortmans, J. R., Newsholme, E. A. Does glutamine have a role in reducing infections in athletes? European journal of applied physiology. 1996; 73: 488-490.
Hack, V., Weiss, C., Friedmann, B., Suttner, S., Schoykowski, M., Erge, N., Benner, A., Barlsch, P., Droge, W. Decreased plasma glutamine level and CD4+ T-cell number in response to 8 weeks of anaerobic training. American journal of physiology. 1997; 272: 788-795.
Garcia, A., Zarazaga, A, et al. Clinical evidence for enteral nutritional support with glutamine: a systemic review. Nutrition. 2003; 19: 805-811.
Den Hond, E., Hiele, M., Peeters, M., et al. Effect of long-term oral glutamine supplementation on small intestinal permeability in patients with Crohn's disease. JPEN journal of parenter enteral nutrition. 1999; 23: 7-11.
Boza, J. J., et al. Free and protein-bound glutamine have identical splanchnic extraction in healthy human volunteers. American journal of physiological gastrointestinal liver physiology. 2001 Jul; 281(1): 267-274.
Glutamine. Whole health MD. 2000; 1-3. http://www.wholehealthmd.com.
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Overtraining in athletes has also been linked to lower plasma glutamine concentrations when compared to athletes that were properly trained. Overtraining occurs as a result of increased intensity, volume, or frequency of workouts while failing to give the body adequate rest. This causes decreased performance, fatigue, depression, and nausea in the athlete (12). Intense training and over training may compromise the immune system by increasing susceptibility to viral and bacteria infections. Low glutamine levels lower the production of T cells and reduce the ability of macrophages to combat viruses and bacteria that may enter the body. The common cold, flu, and HIV have all been linked to lower glutamine levels (13). Oxford University performed a study on over 150 marathon runners in 1996. Half of the subjects received five grams of glutamine after a strenuous run and the other half received a placebo. Subjects that received the placebo were twice as likely to get sick following a marathon run (12). Any athlete engaging in intense, strenuous activity would benefit from supplementing with glutamine solely for its immune system properties allowing them to stay healthy and hence train more frequency.
Glutamine is available in tablets, capsules, and powder form. It is also available in enteral and parenteral nutrition and in some medical foods. Typical doses range from 4 to 21 grams and usually divided up throughout the day. Athletes would take five grams after a workout for maximum benefits (4). Glutamine can be used by strength training and high intensity athletes to prevent muscle break down and reduce sickness, those that are recovering from surgery or a trauma to reduce hospital stay, and people with gastrointestinal symptoms. Glutamine is readily available at any health and nutrition store and is one of few proven safe supplements with no side effects.
