New Study on Carbs, Exercise and the Immune System
Hard exercise is known to temporarily suppress immune system function, as indicated by reduced circulating cytokine levels after prolonged workouts. Carbohydrate ingestion during exercise has been shown to attenuate the immunosupressive effect of hard exercise. However, all of the studies showing this effect have been performed with subjects in a fasted state. Exercise studies are often done with fasted subjects because it minimizes potential effects of disparate eating patterns on experimental results. However, in this case it is reasonable to suspect that pre-exercise fasting might have exaggerated the attenuating effect of carbohydrate consumption during exercise on post-workout immunosupression.
Recently, researchers from the Australian Institute of Sport put this supposition to the test. In this study, 16 highly trained cyclists and triathletes completed two stationary cycling sessions consisting of 100 minutes at 70 percent VO2max followed by a 30-minute time trial. They consumed a high-crbohydrate breakfast two hours before both tests, but then consumed a carbohydrate sports drink during one test and water during the other. The researchers found that circulating levels of two of four cytokines measured were reduced substantially less after the sports drink trial than after the water trial. This was a less marked effect than has been seen in fasted-state studies.
The authors of the study, which was published in the International Journal of Sports Medicine, concluded that "the previously shown attenuating effects of carbohydrate ingestion during exercise on cytokine responses appear reduced when athletes consume a carbohydrate-containing pre-exercise meal." |
