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Pass the Carbohydrates, Please

Intense training can create big muscles and improve speed and performance. But heavy training can also stress athletes' bodies, draining them of the ability to effectively repair themselves or fight off disease. Research has suggested that decreased glutamine, an amino acid formed in the body, might be one reason for impaired immune systems during intense training.

These researchers attempted to understand the way carbohydrates in the diet and intensity of exercise affected glutamine levels in the blood and muscles. They tested five male bike racers during three days of intense exercise on two different diets. One diet regimen provided 45% of the calories from carbohydrates, and the other was 70% carbohydrate. At different times in the study, the athletes' blood was drawn and their muscles were tested to see how much glutamine was present in the muscles.

The study showed that the high-carbohydrate diet resulted in higher levels of glutamine in the blood throughout the days of intense exercise. Concentrations within the muscles, however, were about the same with each diet. The authors noted a small decrease in muscle glutamine while on the lower carbohydrate diet, although it wasn't that significant. They suggest that future research should include more subjects to get a better idea of glutamine concentrations in the muscles.

The study also showed that the amount of dietary carbohydrate did not affect levels of glycogen within the muscles. (Glycogen is basically extra carbohydrates stored in the muscles and liver.) Glycogen is needed to help the body form glutamine. The authors feel it is possible that their study's restriction on eating until two hours after exercise affected this measurement. They also feel it is possible that tissue damage from the intense exercise may have kept the glycogen levels low after exercise.

It appears that a diet higher in carbohydrates reduces the amount of protein taken in by the athlete. The higher carbohydrate diet seems to have had a role in the higher levels of glutamine in the blood. Further research will be needed to help athletes find a diet to maximize their health during periods of intense training.

References: Michelle A. Blanchard, et al. The Influence of Diet and Exercise on Muscle and Plasma Glutamine Concentrations. In Medicine & Science in Sports & Exercise. January 2001. Vol. 33. No. 1. Pp. 69-74.

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