Glutamine is essential for protein synthesis and muscle cell growth. While maintaining glutamine status is critical to hard training athletes and the critically ill, very little research has investigated the most effective nutritional method to enhance glutamine levels.
This study on glucocorticoid-treated rats showed that by adding glutamine to quality proteins like whey, was the most effective way to stimulate protein synthesis rates and grow lean tissue. This study looked at two different ways of enhancing tissue glutamine levels. The rats were treated with a glucocorticoid steroid (intraperitoneal dexamethasone, 120 mg/kg) to induce tissue breakdown. During the recovery period some of the rats were fed either casein, whey, or carob and essential amino acids, while free-form glutamine was added to each of these proteins and fed to other rats.
All the diets were equal in calories and protein content. Plasma and tissue amino acids and glutathione as well as protein synthesis (within muscle and intestines) were measured. The glucocorticoid treatment lowered weight gain, muscle glutamine, and protein synthesis rates. The results showed that protein synthesis rates were increased only when the extra glutamine was included to the diet.
The protein sources alone were only effective at restoring protein synthesis rates within the internal organs but not muscle. Only when free-form glutamine was added did protein synthesis rates increased significantly in muscle tissue. The rats fed the whey plus glutamine demonstrated slightly larger increases in muscle protein synthesis rates than the casein or carob and essential amino acids.
The scientists suggested that in this study the glutamine provided naturally in the protein was extensively metabolized by intestinal tissues and therefore muscle tissue didn’t get enough for anabolism and growth. The only way muscle protein synthesis rates increased was by adding free form glutamine to the dietary protein. Just goes to show how vital glutamine really is to muscle growth.
Glucocorticoid treated rats are still a far cry from bodybuilders. However, the importance of adding glutamine to your high protein diet cannot be underestimated. By keeping your protein intake high and adding a quality glutamine supplement like GL3 may be a way to stimulate protein synthesis rates more effectively and help bust through plateaus in training. In this study, the added glutamine also elevated plasma glutamine levels. Plasma glutamine is the fuel for optimal function of the immune system and internal organs.
This research substantiates my hypothesis that the optimal approach to muscle growth is in a “double-edged sword” involving free-form glutamine and high quality protein. Glutamine supplementation appears to meet the ravenous metabolic demands of internal organs and the immune system allowing the quality proteins such as whey and casein to deliver their amino acids right to muscle cells. This would stimulate more constant, uninterrupted protein synthesis, and create a more permanent state of anabolism within muscle cells.
Nutrition 17(1):35-40
