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I Hope You Haven't Forgot Your Glutamine!
Advertised Claims
Prevents muscle catabolism
Promotes muscle anabolism
Enhances the immune system
Enhances glycogen stores.
Description
Glutamine is classified as a nonessential amino acid since it can be readily synthesized by various tissues such as the skeletal muscles, liver, and adipose tissue. However, research indicates that glutamine is conditionally essential when the metabolic demand for glutamine exceeds the amount available in the free glutamine pool and that which can be provided by de novo synthesis (1).
During exercise or other times of metabolic stress (e.g. fasting, severe injury, illness, etc.), the demand for plasma glutamine markedly increases. For instance, various cells of the immune system such as the lymphocytes and macrophages depend on glutamine as a primary fuel source, and thus the demand for glutamine increases when an immunological response is mounted (2).
The enterocytes of the small intestines are the largest consumers of glutamine accounting for about 40-50% of glutamine consumption. Furthermore, glutamine is required for the synthesis of nucleotides. Thus, a sufficient supply of glutamine is particularly important for rapidly dividing cells such as the enterocytes and the immune cells. Therefore, de novo synthesis of glutamine may be insufficient to meet the physiological demand during times of severe, metabolic stress when the amount of free glutamine is rapidly depleted (3).
The skeletal muscles are the primary sites for glutamine synthesis and storage as glutamine contributes to approximately 60% of the free amino acids within the skeletal muscles. Glutamine is also the most abundant amino acid within the plasma (3). Glucocorticoid hormones such as cortisol are released during such times of stress and promote the proteolysis of muscle proteins and the release of glutamine into the plasma to attenuate the increased demand for free glutamine. During hypoglycemic conditions such as the fasting state (after approximately 12 hours of fasting), the branched-chain amino acids within the muscle undergo the transamination process (under the influence of the glucocorticoid hormones) to yield keto-acids which are available as precursors for gluconeogenesis or ketogenesis (4).
Consequently, glutamate and alanine are generated from their keto-acid counterparts (alpha-keto-glutarate and pyruvate respectively) during the transamination process. Glutamine is synthesized from glutamate and ammonia via glutamine synthetase (4). Glutamine is the most abundant amino acid generated in the muscle tissue during this time since glutamine formation is independent of glycolysis whereas alanine is formed directly from pyruvate, the end product of glycolysis. The majority of nitrogen loss from muscle tissue occurs during the fasting state through glutamine (5).
Glutamine may be metabolized to form glucose in the liver. Under certain conditions (e.g. acidosis), glutamine may also be utilized by the kidneys where it is converted into glutamate and then into alpha-keto-glutarate which enters the renal gluconeogenic pathway. Within the small intestines, glutamine is also metabolized into alanine which is further metabolized by the liver as a gluconeogenic precursor (4).
Commercial Availability and General Use
The cost for a month's supply of glutamine (L-glutamine) ranges from about $14 to $54 and typically is sold in the form of gel capsules and powders. Glutamine is sold in major health/nutrition stores and may be an ingredient in other dietary supplements such as protein powders.
However, glutamine is relatively unstable in solution, and thus glutamine powders must be consumed shortly after being mixed into solution. Some manufacturers of the supplement recommend consuming glutamine in divided dosages throughout the day. It has also been suggested that glutamine be consumed shortly before sleep (a 6-8 hour fast) and after waking.
Ergogenic Effects
Maintenance of muscle mass during physiological stress
Glutamine supplementation may promote nitrogen retention (a positive nitrogen balance) and prevent the loss of muscle protein (6). A decreased ratio of testosterone to cortisol is believed to be directly responsible for losses in muscle mass since cortisol promotes the synthesis of glutamine synthetase. By maintaining intracellular concentrations of glutamine within the skeletal muscles, the synthesis of glutamine synthetase mRNA may be inhibited and thus the loss of intracellular nitrogen through glutamine may be prevented. Furthermore, by enhancing plasma concentrations of glutamine, the demand for free glutamine by other tissues and cells (e.g. the small intestine and immune cells) is attenuated and thus the release of glutamine from muscle tissues is reduced (3).
Research
Hankard et al. Am J Physiol, 1996.
Fourteen subjects received intravenous infusions of leucine to determine whether glutamine infusion inhibits protein breakdown and/or increase the rate of protein synthesis. Seven of these subjects received 800 micromol/kg/hr of glutamine via enteral infusion every other day. Seven other subjects received a similar amount of glycine also via enteral infusion (7).
During the infusion of glutamine, the rate of leucine appearance in the plasma remained unchanged indicating that glutamine supplementation inhibited the breakdown of muscle protein. In addition, the oxidation of leucine decreased and nonoxidative leucine disposal increased indicating an increase in protein synthesis. During glycine infusion, protein breakdown was also inhibited but did not result in an increase in protein synthesis (7).
MacLennan et al. FEBS Lett, 1988.
Glutamine significantly reduced protein breakdown and net protein loss in isolated perfused rat hindlimb skeletal muscle. Protein breakdown was inhibited in the soluble proteins though not in the myofibrillar proteins. Insulin also had a protein sparing effect on the muscle, but did not have as great an effect as glutamine. The combination of insulin and glutamine did not have an additive effect (.
MacLennan et al. FEBS Lett, 1987.
Protein synthesis in isolated perfused rat skeletal muscle (rat hindquarter) increased by 66% when the concentration of intracellular glutamine was increased. This increase in protein synthesis occurred with or without the presence of insulin. Thus it was concluded that increased intramuscular glutamine induced protein synthesis independently of insulin (9).
Hickson et al. Am J Physiol, 1996.
To investigate the effect of glutamine supplementation on glucocorticoid metabolism. Rats were treated with hydrocortisone 21-acetate. An infusion of either alanine or alanyl-glutamine was given to the rats. In an increase in glutamine synthetase activity (and glutamine synthetase mRNA expression) was increased in the plantaris, superficial quadriceps, and deep quadriceps muscles. Compared to the rats treated with alanine, glutamine synthetase activity was 42-65% less in the rats treated with alanyl-glutamine, and glutamine synthetase mRNA expression was 31-37% less in the alanyl-glutamine treated rats as well. Alanyl-glutamine treatment prevented loss in overall body mass and fast-twitch muscle mass by over 70% as compared to alanine treatment. Thus it was concluded that glutamine infusions may have inhibited the catabolic effects of glucocorticoid hormones (10).
Palmer et al. Nutrition, 1996.
(No effect from supplementation)
38 critically ill patients (aged 19-77 years) received total parenteral nutrition (TNP) containing either 25 g glutamine or no glutamine each day. Muscle biopsies were obtained from 19 subjects within this group (glutamine group=10, without glutamine=9) before the feeding period. Another biopsy sample was taken after 5 days of the feeding period (n=16). Biopsy samples indicated no biochemical differences (no change in glutaminase or glutamate dehydrogenase activity) between the group receiving the glutamine supplementation and the group that did not receive glutamine supplementation (11).
Increased muscle cell volume
It has been suggested that glutamine supplementation may induce an anabolic effect as an osmotically active agent. Previous research has indicated that changes in the cellular hydration state (and thus changes in cell volume) may act as a metabolic signal. An increase in cell volume has been associated with cellular anabolism while cell shrinkage has been associated with cellular catabolism (12). Vom Dahl et al. reported that glutamine had an antiproteolytic effect on rat liver cells which was the result of its effect on the cellular hydration state (i.e. increased cell volume). This effect was enhanced when the rats were starved for 24 hours (13).
Enhanced immune system
Cells of the immune system including the macrophages and lymphocytes depend on glutamine as a primary fuel source. In addition, it has been hypothesized that a high rate of glutamine consumption by these rapidly proliferating cells is required for sufficient nucleotide synthesis (14). Research indicates that low levels of glutamine within the body may result in the increased susceptibility to infections and illness due to a suppressed immune system (2). The ability to proliferate and the activity of immune cells in vitro have reportedly been suppressed in mediums lacking glutamine (15).
Furthermore, an increased rate of infection and illness (particularly infections of the upper respiratory tract) has been reported among athletes participating in intense, long duration sports activities (e.g. marathon racing) (16). It has been suggested that a decline in plasma glutamine concentrations may be one of the factors responsible for this increased rate of illness. Specifically, the activity of natural killer cells, a reduced number and proliferative ability of lymphocytes, and a reduced ratio of T-helper to T-suppressor cells may be the result of prolonged, exhaustive exercise (16).
Research
Castell et al. Eur J Appl Physiol, 1996.
The rate of infections were investigated in athletes participating in four different types of endurance sports/exercises including marathon racing, ultra-marathon racing, middle distance running (either 15-mile training or 10-km racing), and commando-style rowing. The subjects were given 5-g of glutamine in 330 ml water or a placebo (Malto-dextrin) immediately after their event and then again two hours later (2).
Plasma levels of glutamine were measured in the marathon runners and in the middle-distance runners. Questionnaires were used to determine the rate of infections over a period of seven days for all the subjects. The subjects were asked to report symptoms of colds, sore throats, influenza, diarrhea, and vomiting (2).
The percentage of infections was greatest in the rowers (55%), and a similar percentage of illnesses were reported among the marathon and ultra-marathon runners (about 47% and 48% respectively). The middle-distance runners reported far fewer infections (25%). In addition, 80% of the subjects who consumed glutamine reported no infections while only 49% of the subjects that consumed the placebo reported no infections (2).
Keast et al. Med J Aust, 1995.
Two separate trials were performed in this study to observe plasma glutamine levels after exercise. In the first trial, seven male subjects performed a treadmill test at 0, 30%, 60%, 90%, and 120% of maximal oxygen uptake. Plasma glutamine levels dropped significantly after the tests at 90% VO2max and at 120% VO2max. In the second trial, 5 highly-trained male subjects performed intense, exercise sessions (interval training) twice a day for 10 days. The subjects were then examined over a 6 day recovery period. By day 6 of the exercise period, plasma glutamine levels dropped significantly in 4 of the 5 subjects. By the first day of the recovery period, glutamine levels had dropped significantly in all 5 of the subjects. The plasma levels of glutamine remained low even after the sixth day of recovery in two of the subjects (17).
Castell et al. Eur J Appl Physiol, 1997.
(No effect from supplementation)
18 male athletes participated in a marathon. Blood samples were obtained 30 minutes before the event, within 15 minutes after the event, one hour after the event , and then at 16 hours after the event. The subjects received either 5 g of glutamine (n=10) or 5 g Malto dextrin (n= after the second blood sample and then again at one hour after the marathon. The blood samples indicated no significant differences in plasma lymphocyte distribution between the glutamine group and the placebo group following the marathon (18).
Glucose and glycogen formation
The carbon skeleton of glutamine can serve as a gluconeogenic precursor and may regulate gluconeogenesis independently of the insulin/glucagon ratio. Because glutamine may serve as a precursor to glucose independently of glucacon regulation, glutamine supplementation may also enhance glycogenolysis and thus increase muscle glycogen stores even when insulin levels are low (19,20).
Research
Varnier et al. Am J Physiol, 1995.
Groups of six subjects each cycled for 90 minutes at a moderate to very high-intensity (70 to 140% VO2 max). The exercise protocol was designed to deplete glycogen stores. Following exercise, the subjects were infused with 30 mg/kg body weight of either glutamine, alanine+glycine, or a saline solution. Two hours following exercise, muscle glycogen concentration increased significantly more in the subjects receiving glutamine than the subjects in the other groups (19).
Perriello et al. Am J Physiol, 1997.
Sixteen normal, postabsorptive human subjects were infused with glutamine such that the glutamine appeared in the plasma at a rate similar to that observed following a high-protein meal. The amount of glucose formed from glutamine within the subjects increased by seven times independently of glucagon/insulin regulation (20).
Risks and Disadvantages
Research has indicated that glutamine supplementation is safe for humans (21). However, there is little data regarding long-term usage (more than a few weeks) of glutamine supplements Furthermore, more research needs to be conducted to investigate the safety of glutamine supplementation at doses that are posited to promote nitrogen retention in the muscles.
Generally speaking, the consumption of any one, single amino acid in large doses may inhibit the absorption of other amino acids since amino acids (basic and neutral amino acids) tend to compete for transport across the intestinal epithelium. However, a study performed by Dechelotte et al. reported that glutamine is absorbed effectively in the small intestine (22).
The consumption of large doses of free amino acids may result in intestinal discomfort (e.g. abdominal pains and diarrhea) due to the electrolyte-like properties of the amino-acids.
Recommendations
Several studies have shown that glutamine supplementation may help prevent protein loss in patients suffering from various forms of trauma/physiological stress. These findings suggest potential for glutamine as a sports nutrition supplement, but further research is warranted.
I Hope You Haven't Forgot Your Glutamine!
Advertised Claims
Prevents muscle catabolism
Promotes muscle anabolism
Enhances the immune system
Enhances glycogen stores.
Description
Glutamine is classified as a nonessential amino acid since it can be readily synthesized by various tissues such as the skeletal muscles, liver, and adipose tissue. However, research indicates that glutamine is conditionally essential when the metabolic demand for glutamine exceeds the amount available in the free glutamine pool and that which can be provided by de novo synthesis (1).
During exercise or other times of metabolic stress (e.g. fasting, severe injury, illness, etc.), the demand for plasma glutamine markedly increases. For instance, various cells of the immune system such as the lymphocytes and macrophages depend on glutamine as a primary fuel source, and thus the demand for glutamine increases when an immunological response is mounted (2).
The enterocytes of the small intestines are the largest consumers of glutamine accounting for about 40-50% of glutamine consumption. Furthermore, glutamine is required for the synthesis of nucleotides. Thus, a sufficient supply of glutamine is particularly important for rapidly dividing cells such as the enterocytes and the immune cells. Therefore, de novo synthesis of glutamine may be insufficient to meet the physiological demand during times of severe, metabolic stress when the amount of free glutamine is rapidly depleted (3).
The skeletal muscles are the primary sites for glutamine synthesis and storage as glutamine contributes to approximately 60% of the free amino acids within the skeletal muscles. Glutamine is also the most abundant amino acid within the plasma (3). Glucocorticoid hormones such as cortisol are released during such times of stress and promote the proteolysis of muscle proteins and the release of glutamine into the plasma to attenuate the increased demand for free glutamine. During hypoglycemic conditions such as the fasting state (after approximately 12 hours of fasting), the branched-chain amino acids within the muscle undergo the transamination process (under the influence of the glucocorticoid hormones) to yield keto-acids which are available as precursors for gluconeogenesis or ketogenesis (4).
Consequently, glutamate and alanine are generated from their keto-acid counterparts (alpha-keto-glutarate and pyruvate respectively) during the transamination process. Glutamine is synthesized from glutamate and ammonia via glutamine synthetase (4). Glutamine is the most abundant amino acid generated in the muscle tissue during this time since glutamine formation is independent of glycolysis whereas alanine is formed directly from pyruvate, the end product of glycolysis. The majority of nitrogen loss from muscle tissue occurs during the fasting state through glutamine (5).
Glutamine may be metabolized to form glucose in the liver. Under certain conditions (e.g. acidosis), glutamine may also be utilized by the kidneys where it is converted into glutamate and then into alpha-keto-glutarate which enters the renal gluconeogenic pathway. Within the small intestines, glutamine is also metabolized into alanine which is further metabolized by the liver as a gluconeogenic precursor (4).
Commercial Availability and General Use
The cost for a month's supply of glutamine (L-glutamine) ranges from about $14 to $54 and typically is sold in the form of gel capsules and powders. Glutamine is sold in major health/nutrition stores and may be an ingredient in other dietary supplements such as protein powders.
However, glutamine is relatively unstable in solution, and thus glutamine powders must be consumed shortly after being mixed into solution. Some manufacturers of the supplement recommend consuming glutamine in divided dosages throughout the day. It has also been suggested that glutamine be consumed shortly before sleep (a 6-8 hour fast) and after waking.
Ergogenic Effects
Maintenance of muscle mass during physiological stress
Glutamine supplementation may promote nitrogen retention (a positive nitrogen balance) and prevent the loss of muscle protein (6). A decreased ratio of testosterone to cortisol is believed to be directly responsible for losses in muscle mass since cortisol promotes the synthesis of glutamine synthetase. By maintaining intracellular concentrations of glutamine within the skeletal muscles, the synthesis of glutamine synthetase mRNA may be inhibited and thus the loss of intracellular nitrogen through glutamine may be prevented. Furthermore, by enhancing plasma concentrations of glutamine, the demand for free glutamine by other tissues and cells (e.g. the small intestine and immune cells) is attenuated and thus the release of glutamine from muscle tissues is reduced (3).
Research
Hankard et al. Am J Physiol, 1996.
Fourteen subjects received intravenous infusions of leucine to determine whether glutamine infusion inhibits protein breakdown and/or increase the rate of protein synthesis. Seven of these subjects received 800 micromol/kg/hr of glutamine via enteral infusion every other day. Seven other subjects received a similar amount of glycine also via enteral infusion (7).
During the infusion of glutamine, the rate of leucine appearance in the plasma remained unchanged indicating that glutamine supplementation inhibited the breakdown of muscle protein. In addition, the oxidation of leucine decreased and nonoxidative leucine disposal increased indicating an increase in protein synthesis. During glycine infusion, protein breakdown was also inhibited but did not result in an increase in protein synthesis (7).
MacLennan et al. FEBS Lett, 1988.
Glutamine significantly reduced protein breakdown and net protein loss in isolated perfused rat hindlimb skeletal muscle. Protein breakdown was inhibited in the soluble proteins though not in the myofibrillar proteins. Insulin also had a protein sparing effect on the muscle, but did not have as great an effect as glutamine. The combination of insulin and glutamine did not have an additive effect (.
MacLennan et al. FEBS Lett, 1987.
Protein synthesis in isolated perfused rat skeletal muscle (rat hindquarter) increased by 66% when the concentration of intracellular glutamine was increased. This increase in protein synthesis occurred with or without the presence of insulin. Thus it was concluded that increased intramuscular glutamine induced protein synthesis independently of insulin (9).
Hickson et al. Am J Physiol, 1996.
To investigate the effect of glutamine supplementation on glucocorticoid metabolism. Rats were treated with hydrocortisone 21-acetate. An infusion of either alanine or alanyl-glutamine was given to the rats. In an increase in glutamine synthetase activity (and glutamine synthetase mRNA expression) was increased in the plantaris, superficial quadriceps, and deep quadriceps muscles. Compared to the rats treated with alanine, glutamine synthetase activity was 42-65% less in the rats treated with alanyl-glutamine, and glutamine synthetase mRNA expression was 31-37% less in the alanyl-glutamine treated rats as well. Alanyl-glutamine treatment prevented loss in overall body mass and fast-twitch muscle mass by over 70% as compared to alanine treatment. Thus it was concluded that glutamine infusions may have inhibited the catabolic effects of glucocorticoid hormones (10).
Palmer et al. Nutrition, 1996.
(No effect from supplementation)
38 critically ill patients (aged 19-77 years) received total parenteral nutrition (TNP) containing either 25 g glutamine or no glutamine each day. Muscle biopsies were obtained from 19 subjects within this group (glutamine group=10, without glutamine=9) before the feeding period. Another biopsy sample was taken after 5 days of the feeding period (n=16). Biopsy samples indicated no biochemical differences (no change in glutaminase or glutamate dehydrogenase activity) between the group receiving the glutamine supplementation and the group that did not receive glutamine supplementation (11).
Increased muscle cell volume
It has been suggested that glutamine supplementation may induce an anabolic effect as an osmotically active agent. Previous research has indicated that changes in the cellular hydration state (and thus changes in cell volume) may act as a metabolic signal. An increase in cell volume has been associated with cellular anabolism while cell shrinkage has been associated with cellular catabolism (12). Vom Dahl et al. reported that glutamine had an antiproteolytic effect on rat liver cells which was the result of its effect on the cellular hydration state (i.e. increased cell volume). This effect was enhanced when the rats were starved for 24 hours (13).
Enhanced immune system
Cells of the immune system including the macrophages and lymphocytes depend on glutamine as a primary fuel source. In addition, it has been hypothesized that a high rate of glutamine consumption by these rapidly proliferating cells is required for sufficient nucleotide synthesis (14). Research indicates that low levels of glutamine within the body may result in the increased susceptibility to infections and illness due to a suppressed immune system (2). The ability to proliferate and the activity of immune cells in vitro have reportedly been suppressed in mediums lacking glutamine (15).
Furthermore, an increased rate of infection and illness (particularly infections of the upper respiratory tract) has been reported among athletes participating in intense, long duration sports activities (e.g. marathon racing) (16). It has been suggested that a decline in plasma glutamine concentrations may be one of the factors responsible for this increased rate of illness. Specifically, the activity of natural killer cells, a reduced number and proliferative ability of lymphocytes, and a reduced ratio of T-helper to T-suppressor cells may be the result of prolonged, exhaustive exercise (16).
Research
Castell et al. Eur J Appl Physiol, 1996.
The rate of infections were investigated in athletes participating in four different types of endurance sports/exercises including marathon racing, ultra-marathon racing, middle distance running (either 15-mile training or 10-km racing), and commando-style rowing. The subjects were given 5-g of glutamine in 330 ml water or a placebo (Malto-dextrin) immediately after their event and then again two hours later (2).
Plasma levels of glutamine were measured in the marathon runners and in the middle-distance runners. Questionnaires were used to determine the rate of infections over a period of seven days for all the subjects. The subjects were asked to report symptoms of colds, sore throats, influenza, diarrhea, and vomiting (2).
The percentage of infections was greatest in the rowers (55%), and a similar percentage of illnesses were reported among the marathon and ultra-marathon runners (about 47% and 48% respectively). The middle-distance runners reported far fewer infections (25%). In addition, 80% of the subjects who consumed glutamine reported no infections while only 49% of the subjects that consumed the placebo reported no infections (2).
Keast et al. Med J Aust, 1995.
Two separate trials were performed in this study to observe plasma glutamine levels after exercise. In the first trial, seven male subjects performed a treadmill test at 0, 30%, 60%, 90%, and 120% of maximal oxygen uptake. Plasma glutamine levels dropped significantly after the tests at 90% VO2max and at 120% VO2max. In the second trial, 5 highly-trained male subjects performed intense, exercise sessions (interval training) twice a day for 10 days. The subjects were then examined over a 6 day recovery period. By day 6 of the exercise period, plasma glutamine levels dropped significantly in 4 of the 5 subjects. By the first day of the recovery period, glutamine levels had dropped significantly in all 5 of the subjects. The plasma levels of glutamine remained low even after the sixth day of recovery in two of the subjects (17).
Castell et al. Eur J Appl Physiol, 1997.
(No effect from supplementation)
18 male athletes participated in a marathon. Blood samples were obtained 30 minutes before the event, within 15 minutes after the event, one hour after the event , and then at 16 hours after the event. The subjects received either 5 g of glutamine (n=10) or 5 g Malto dextrin (n= after the second blood sample and then again at one hour after the marathon. The blood samples indicated no significant differences in plasma lymphocyte distribution between the glutamine group and the placebo group following the marathon (18).
Glucose and glycogen formation
The carbon skeleton of glutamine can serve as a gluconeogenic precursor and may regulate gluconeogenesis independently of the insulin/glucagon ratio. Because glutamine may serve as a precursor to glucose independently of glucacon regulation, glutamine supplementation may also enhance glycogenolysis and thus increase muscle glycogen stores even when insulin levels are low (19,20).
Research
Varnier et al. Am J Physiol, 1995.
Groups of six subjects each cycled for 90 minutes at a moderate to very high-intensity (70 to 140% VO2 max). The exercise protocol was designed to deplete glycogen stores. Following exercise, the subjects were infused with 30 mg/kg body weight of either glutamine, alanine+glycine, or a saline solution. Two hours following exercise, muscle glycogen concentration increased significantly more in the subjects receiving glutamine than the subjects in the other groups (19).
Perriello et al. Am J Physiol, 1997.
Sixteen normal, postabsorptive human subjects were infused with glutamine such that the glutamine appeared in the plasma at a rate similar to that observed following a high-protein meal. The amount of glucose formed from glutamine within the subjects increased by seven times independently of glucagon/insulin regulation (20).
Risks and Disadvantages
Research has indicated that glutamine supplementation is safe for humans (21). However, there is little data regarding long-term usage (more than a few weeks) of glutamine supplements Furthermore, more research needs to be conducted to investigate the safety of glutamine supplementation at doses that are posited to promote nitrogen retention in the muscles.
Generally speaking, the consumption of any one, single amino acid in large doses may inhibit the absorption of other amino acids since amino acids (basic and neutral amino acids) tend to compete for transport across the intestinal epithelium. However, a study performed by Dechelotte et al. reported that glutamine is absorbed effectively in the small intestine (22).
The consumption of large doses of free amino acids may result in intestinal discomfort (e.g. abdominal pains and diarrhea) due to the electrolyte-like properties of the amino-acids.
Recommendations
Several studies have shown that glutamine supplementation may help prevent protein loss in patients suffering from various forms of trauma/physiological stress. These findings suggest potential for glutamine as a sports nutrition supplement, but further research is warranted.
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