Friday, October 14, 2011

Glutamine: The Muscle Amino ..Or is it? by Jerry Brainum

   Glutamine was a relatively obscure amino acid until a few years ago. It was considered a nonessential amino acid, meaning that it could be synthesized in the body from other amino acids, such as glutamic acid and the branched-chain aminos. In addition, the body content of glutamine is extensive, with glutamine composing half the free amino acids found in muscle and blood.

   More recently, however, glutamine became recognized as a conditionally essential amino acid, meaning that under certain specific conditions the body can’t provide sufficient glutamine to meet its needs, and thus an outside source is necessary. That first became apparent in critically ill hospital patients, especially those suffering massive loss of protein, such as burn patients or those recovering from major surgical procedures. Plasma levels of glutamine dropped rapidly in such patients, and the skeletal muscles became catabolic. Muscle protein was broken down to provide free glutamine to support body functions.

   Doctors soon realized that giving glutamine to those patients rapidly ended the catabolic muscle conditions. Glutamine proved to be a potent anticatabolic nutrient. The information trickled down to the athletic community, including bodybuilders, and the reputation of glutamine as a “muscle amino acid” emerged.

   Various studies show that intense exercise can induce a type of immune suppression that glutamine can counter. Intense exercise causes a loss of glutamine, and certain immune cells use it as a primary fuel. So a lack of glutamine may adversely affect your immune system.

   Intense exercise also promotes a rise in cortisol, the major catabolic hormone in the body. Cortisol breaks down amino acids found in muscle. Some studies show that glutamine opposes that effect of cortisol, thereby sparing muscle amino acids and preventing muscle catabolism. Other studies show that glutamine may favorably affect muscle glycogen synthesis, which would positively affect recuperation and recovery after hard training.

  Glutamine has been linked to increased muscle protein synthesis. It’s among the most potent stimulators of cellular hydration, or incorporation of water into cells. Cell hydration, in turn, induces a process that results in upgraded anabolism, or protein synthesis. Another way that glutamine may help foster muscle gains is by increasing the release of growth hormone.

   But not all studies show that glutamine is useful for bodybuilding purposes. In one, presented at the 2005 meeting of the American College of Sports Medicine by researchers from Ohio, 12 men were randomly assigned to either a glutamine or a placebo group (six men in each group).1 All the subjects trained with weights twice a week for seven weeks, using only three exercises: bench presses, shoulder presses and squats. They did three sets of each exercise. They got 10 grams a day in four divided doses of either a glucose placebo or glutamine, twice daily on training days (before workout and before bed).

   After seven weeks the groups showed no differences in strength increases or body composition. That led to the conclusion that glutamine was ineffective for increasing strength or changing body composition.

   The problem with the study is that other studies have shown glutamine to be most useful under conditions of intense training that borders on overtraining. Unless a catabolic stimulus is induced in muscle, glutamine is nearly useless. The routine listed in this study was neither intense nor anywhere close to being catabolic. So we wouldn’t expect glutamine to provide any benefits. We also don’t know whether the study subjects were on a high-protein diet, which could also influence the results, as would carbohydrate intake; lowering carbs increases the need for glutamine under hard-training conditions. The Ohio study is hardly the final word on glutamine.

1 Thistlethwaite, J.R., et al. (2005). The effects of glutamine on muscle strength and body composition. Med Sci Sports Exer. 37:S45.

©,2013 Jerry Brainum. Any reprinting in any type of media, including electronic and foreign is expressly prohibited.

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