Supplement Performance - Glutamine and Gym Rats: A Critical Review
“I know that most men, including those at ease with problems of the greatest complexity, can seldom accept even the simplest and most obvious truth if it be such as would oblige them to admit the falsity of conclusions which they have delighted in explaining to colleagues, which they have proudly taught to others, and which they have woven, thread by thread, into the fabric of their lives.” —Tolstoy
Basic Facts About Glutamine
Glutamine is one of the most abundant amino acids in the body, composing about 50 percent of the free amino acid pool in the blood and skeletal muscle. It’s classified as a nonessential amino acid since it can be produced in the body from the other amino acids. Under certain conditions, however, glutamine can become a conditionally essential amino acid. That is, diet and/or supplements may be required to meet the needs of the body.
In situations of stress (e.g., strenuous exercise, clinical trauma), the concentration of glutamine in the blood is decreased, often substantially. In endurance athletes this decrease occurs concomitantly with relatively transient immunodepression (i.e., suppression of natural immune responses). Provision of glutamine or glutamine precursors (e.g., BCAAs) have been seen to have beneficial effects in clinical studies. However, it is not clear if glutamine supplementation is beneficial for healthy gym rats. This article separates fact from fiction.
Glutamine and Growth Hormone Secretion
In 1995, Dr. TC Welbourne at Louisiana State University College of Medicine reported that glutamine supplementation can increase secretion of growth hormone. Two grams of glutamine were dissolved in a cola drink and ingested over a 20-minute period 45 minutes after a light breakfast. The conclusion was that a surprisingly small glutamine load is capable of elevating blood growth hormone. This study was prominently cited in the leading bodybuilding magazines, so gym rats started to ingest supplemental glutamine like there’s no tomorrow.
Glutamine, Strength and Body Composition
More recently, Dr. D.G. Candow and colleagues at the University of Saskatchewan in Canada assessed the effects of oral glutamine supplementation combined with resistance training in young adults. A group of 31 subjects were randomly allocated to groups to receive either glutamine (0.9 grams per kilogram of lean tissue mass per day) or a placebo (maltodextrin) during six weeks of resistance training. Exercises were performed for four to five sets of six to 12 repetitions at intensities ranging from 60 to 90 percent of one repetition maximum (1-RM). Before and after training, measurements were taken of 1-RM squat and bench press strength, peak knee extension torque, lean tissue mass and muscle protein degradation.
The results of this study showed no effect of glutamine on any of the dependent variables measured. However, there appeared to be a trend toward a greater muscle protein breakdown in the placebo group. The authors concluded, “Glutamine supplementation did not have a beneficial effect on the adaptations to strength training. While glutamine supplementation has been shown to have beneficial effects following endurance-type exercise, strength training may not be stressful enough to benefit from glutamine supplementation. Future research should look at the effect of glutamine supplementation during training protocols that provide a greater physiological stress, such as combined endurance and strength training.”
Given the fact that about 50-60 percent of dietary glutamine is used by intestinal cells, very high amounts of glutamine would have to be consumed orally to have significant effect on muscle levels. So, glutamine supplementation per se probably does not have a direct effect on bodybuilding in terms of muscle mass increase. Nevertheless, it is possible that supplemental glutamine would have some effect on muscle glutamine during a low-calorie diet. High doses of intravenous glutamine (in dipeptide form) given to markedly catabolic patients have been very effective in preventing the decrease in muscle glutamine that occurs due to muscle wasting.
Glutamine and Immunodepression
In situations of stress (e.g., strenuous exercise), the concentration of glutamine in the blood is decreased, and the decrease occurs concomitantly with relatively transient immunodepression, at least in endurance athletes. There is a growing body of evidence showing that glutamine has an important role in enhancing some aspects of immune cell function. Furthermore, clinical studies have indicated that glutamine supplementation contributes to the alleviation of infections and improved gastrointestinal function. Also, a reduction in the incidence of infections in endurance athletes has been attributed to glutamine supplementation. However, there are no studies examining the effects of glutamine supplementation on infections in strength-power athletes.
Summing Up
A recent study reported that glutamine supplementation during resistance training has no significant effect on muscle performance or body composition degradation in young healthy adults. However, there appeared to be a trend toward greater muscle protein breakdown in the placebo group. Glutamine may have some health benefits (e.g., enhanced immune cell function), but it probably does not have a direct effect on bodybuilding in terms of muscle mass increase.
Glutamine supplementation may be most effective when given to restore glutamine to physiological (i.e., “normal”) levels at a time of depletion due to stress, for example, after strenuous exercise. Glutamine supplements should not be added to hot beverages because heat can destroy the amino acid. Finally, this author believes glutamine peptides are a more effective source of glutamine than free-form glutamine since the peptide form is better absorbed.
