Glutamine can help prevent muscle catabolism, promote muscle anabolism, enhances the immune system, and enhances glycogen storage. Learn how it can help you!
Glutamine is a very common supplement found in many bodybuilders’ gym bags and in their protein shakes, yet it is also a nonessential amino acid that is overlooked by many in their quest in gaining muscle. Over the years, bodybuilders have begun to realize the advertised benefits of glutamine such as  prevents muscle catabolism which is basically the tearing down of muscle,  promotes muscle anabolism, which is basically muscle growth,  enhances the immune system, and  enhances glycogen storage.
WHAT IS GLUTAMINE?
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. Glutamine is the most abundant single amino acid found in the bloodstream, which comprises 61% of the free intracellular amino acid pool [most abundant amino acid in muscle tissue], while Branch Chain Amino Acids [BCAA’S] comprise 8.4% of the pool[11,24]. Glutamine’s unique structure, containing two nitrogen side chains, consists of 19% nitrogen - making it the primary transporter of nitrogen into the muscle cells [10,23].
In the past couple years, Glutamine has gained importance through new studies revealing its unique contribution to protein synthesis [muscle growth], anti-catabolic [prevents muscle tissue] breakdown functions and growth hormone elevating effects. Due to these effects, Glutamine plays an important part in your body by aiding recovery of muscle cells.
WHAT DOES GLUTAMINE DO?
During exercise or other times of metabolic stress such as a precontest diet, severe injury, illness, etc., the demand for glutamine in your blood matrix (plasma) 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 . Macrophages and lymphocytes are the primary virus and bacteria fighters in your bloodstream.
As glutamine travels through the body, the enterocytes of the small intestines are the largest consumers of glutamine accounting for about 40-50% of glutamine consumption. Also, 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, the 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 . Therefore, it may be beneficial for people, who continuously place themselves in infectious areas or commonly get sick, to supplement with glutamine to aid virus/bacteria fighting cells. Glutamine supplementation may also promote nitrogen retention [a positive nitrogen balance] and prevent the loss of muscle protein [4,6]. 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. By maintaining intracellular concentrations of glutamine within the skeletal muscles, the synthesis of glutamine mRNA may be inhibited resulting in the loss of intracellular nitrogen through glutamine may be prevented.
Therefore, it may be beneficial for bodybuilders, who continuously place themselves through strenuous workouts, to supplement with glutamine to aid when glutamine stores are depleted. 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 .
WHY DOES YOUR BODY NEED GLUTAMINE?
To fully understand why glutamine is beneficial to the body we must all endure a little Biochemistry lesson. The body uses glutamine to shuttle ammonia around in the body, so blood levels of glutamine try to maintain constant. Glutamine is craved by the digestive tract and the immune system as a fuel. Most bodybuilders eat more than enough protein from the supermarket, but they do not get enough glutamine through the digestion of meats and other proteins.
The muscles cells are the giant storehouses of glutamine. Under certain pathological circumstances the body’s tissues need more glutamine than the overall amount supplied by diet and natural synthesis such as during a bodybuilder’s strenuous workout[5,24].
During catabolic stress, for instance, intracellular glutamine levels can drop more than 50 percent, and plasma concentration can fall by 30 percent. It is under these circumstances that supplemental glutamine becomes necessary.
Skeletal muscle contains the greatest intracellular concentration of glutamine, comprising up to 60 percent of total body glutamine stores, and is considered the primary storage depot of glutamine, and thus the primary exporter of glutamine to other tissues . In times of metabolic stress, glutamine is released into circulation, where it is transported to the tissue in need. Intracellular skeletal muscle glutamine concentration is affected by various assaults including injury, sepsis, prolonged stress, and starvation. Besides skeletal muscle, the lungs are the next largest producer of glutamine[9,12].
Glutamine is especially useful postworkout when nutrients are at a low until recovery. In this condition research shows glutamine levels are significantly reduced, taking up to one month to return to baseline[ 4]. In athletes, glutamine has been used as a marker to indicate overtraining. This fall in glutamine is catabolic to muscle tissue. BCAA’s [comprising 37% of total muscle] are debranched from skeletal muscle, and the resulting molecules are used to synthesis glutamine.
In the catabolic state, glutamine is the first amino acid used to correct that deficiency. Glutamine drives protein into the muscle cell where it is synthesized for growth[6,8]. This means that additional Glutamine is necessary during periods of stress [such as intense weight training which induces a catabolic state which has been shown to uniformly decrease Glutamine levels by 50%, taking several hours to return to normal levels. Additionally, L-Glutamine also decreases protein degradation [BCAA catabolism], resulting in bigger, stronger muscle cells.
In a recent study of glutamine’s role enhancing the immune system, glutamine demonstrated that increased levels of glutamine leads to greater amounts of virus and infection fighting cells, T and B Lymphocytes. 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 .
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 . The ability to reproduce and the activity of immune cells in vitro have reportedly been suppressed in trials lacking glutamine . Tests also demonstrated that the 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] .
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 proliferate ability of lymphocytes, and a reduced ratio of T-helper to T-suppressor cells may be the result of prolonged, exhaustive exercise . In another study of glutamine’s role on glucose and glycogen formation, the importance of glutamine was also emphasized. The human carbon based skeleton of glutamine can serve as a gluconeogenic precursor and may regulate gluconeogenesis, which is basically the production of glycogen, 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].
So basically glutamine helps regulate glycogen in your body when levels are low and may even increase them, which would result in better performance and growth. In a study by Varnier et al. Am J Physiol in 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 .
BENEFITS & POSSIBLE DISADVANTAGES OF GLUTAMINE SUPPLEMENTATION
In the past several years, research has indicated that glutamine supplementation is safe for humans . 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 .
Other research has indicted that 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.
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