Friday, July 30, 2010

Is glutamine useless? by Jerry Brainum

Glutamine is a conditionally essential amino acid that comprises 60% of the amino acid content of muscle. In fact, 90% of the glutamine produced in the body is synthesized in muscle, with much of it made from branched-chain amino acids. Glutamine is a popular bodybuilding supplement based on the notion that it is anticatabolic; that is, it will help prevent excessive muscle tissue breakdown. But a few recent studies have implied that glutamine us useless as an ergogenic aid for bodybuilding purposes. Some of these studies point out that while 60 gram infusions of intravenous glutamine provided to burn patients, who lose massive amounts of protein each day, does appear to foster decreased muscle tissue losses, it's a far cry to suggest that it does the same for healthy young bodybuilders and athletes.
   In fact, several of these studies provided glutamine to bodybuilders, finding little or no efficacy associated with glutamine when compared to a placebo. But an often overlooked aspect of these studies is that whether glutamine will provide any benefit to bodybuilders depends on how hard a bodybuilder is training, and what degree of stress that bodybuilder is experiencing. Glutamine is considered "conditionally essential" because normally the body can synthesize enough of it from other amino acids, such as glutamic acid and branched-chain amino acids. But under conditions of heightened stress, the body is not capable of producing sufficient glutamine, and in that circumstance, it becomes essential. It's well established that excessive stress, including the stress of extreme training and lack of sleep, can seriously impair immune system functioning. Glutamine is the preferred fuel for certain immune cells, and studies show that supplementing glutamine can help ease the effects of stress on immmune function. Doing so may prevent the onset of various diseases related to a drop in immunity. Glutamine is also the preferred fuel for cells that line the intestine.These cells are replaced about every three days, and use glutamine for purposes of cellular renewal processes.
       Glutamine may be helpful to hard-training athletes and bodybuilders because it interferes with the catabolic activity of cortisol in muscle. Other studies show that glutamine blocks the actions of myostatin in muscle. Myostatin is a protein that promotes muscle loss due to interference with various muscle protein synthesis factors. In the most recent study, involving isolated muscle cells, glutamine was found to block the activity of still another potent muscle breakdown substance, tissue necrosis factor-A (TNF-A). TNF is a cytokine involved in inflammatory reactions in the body. Recent research shows that it's also a major player in the loss of muscle with age that is called sarcopenia. In fact, studies with animals show that if you block the effects of TNF-A on aged muscle, the usual loss of muscle with age is completely halted. This has extremely important implications for those of us past age 40, since muscle loss is the primary cause of age-related frailty. TNF-A also interacts with both cortisol and myostatin to promote the breakdown of muscle, and it appears that glutamine works against all three.
      Does this mean that you should load up on massive amounts of glutamine? It won't do much good, since large oral doses of glutamine are quickly gobbled up by the intestinal cells that love glutamine the way that I love a good New York cheese pizza or potato kinish. But small doses ingested more frequently, such as no more than 5 grams at a time, will allow enough glutamine to sneak by those ravenous intestinal cells and make it into the blood. But be aware that glutamine works best only if you are in a near catabolic state, such as may occur with overtraining, lack of sleep, and other forms of extreme stress. For those just trying to keep in shape, glutamine isn't necessary. On the other hand, if you ingest a low carb diet, glutamine will help preserve muscle, since you lose an average of 25% of glutamine stores in the body while on a low carb regime.

 Bonetto A, et al. Glutamine prevents myostatin hyperexpression and protein hypercatabolism induced in C2C-12 myotubes by tumor necrosis factor-A.Amino Acids 2010: in press.


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