Placid Acid?

Glutamine has emerged in the past few years as one of the most popular amino acid supplements. Although not considered an essential amino acid’because it can be synthesized in the body’some experts consider it ‘conditionally essential,’ since under certain high-stress conditions the body may not produce enough of it. Most of the research showing its beneficial effects involves catabolic hospital patients such as burn victims.

Glutamine can blunt the loss of protein in catabolic patients, and so, by implication, it may help bodybuilders and athletes, whose activities may put them in fleeting near-catabolic states. Studies done with hard-training athletes also show that glutamine may counter the immune-system-suppressing effect that occurs after extended or particularly intense exercise by blunting the catabolic effects of cortisol, an adrenal steroid ‘stress’ hormone.

The supposed attributes of glutamine have led to its incorporation into many food supplements favored by bodybuilders, including protein powders, meal replacements and various types of isolated-glutamine supplements. Few people question the safety of using large amounts of glutamine, but how safe is it?

According to studies in which hospitalized patients got as much as 60 grams of glutamine daily, glutamine is extremely safe. Some self-styled experts have noted that when amino acids are used in isolation’that is, taken one at a time in large doses’an amino acid imbalance can result. While that’s sometimes true, it doesn’t apply to glutamine because glutamine has its own metabolic pathway, which doesn’t conflict with any other amino acids. (So the advice to take glutamine alone, without other aminos or protein supplements, doesn’t make any biochemical sense.)

Even the experts often are wrong about glutamine and other aspects of sports nutrition. One of them, while confirming glutamine’s safety, also notes that ‘glutamine administration has not been demonstrated to result in elevated secretion of any hormone.’1 A study did find that as little as two grams of glutamine led to a significant release of growth hormone. On the other hand, growth hormone release is a complex process, and it would be foolhardy to label glutamine a ‘GH releaser’ on the basis of the minimal existing research.

Perhaps the main problem with glutamine is its inherent instability in fluids. Within a short time of being added to a fluid medium, it’s degraded into two other compounds, and the amino acid activity is lost. One solution is to provide glutamine in peptide form’that is, attached to other amino acids. Studies show that glutamine peptides are more stable in solution than is free-form glutamine. Many glutamine supplement companies are aware of that, and do use glutamine in peptide form in their products. IM

1 Garlick, P.J. (2001). Assessment of the safety of glutamine and other amino acids. J Nutr. 131:2556S-2561S.