Carbohydrate supplementation during intense exercise and the immune response of cyclists

To evaluate the effect of carbohydrate supplementation upon some aspects of the immune function in athletes during intense indoor cycling.

Twelve male athletes cycled for 20 min at a velocity corresponding to 90% of that obtained at the anaerobic threshold and rested for 20 min. This protocol was repeated six times. The athletes received, during the trial, water ad libitum, or a solution of carbohydrate (95% glucose polymers and 5% fructose) at 10% (w/v), 1 g kg h every 20 min, starting at the 10th minute of the first exercise period, plus extra water ad libitum.

Exercise induced a reduction in peripheral blood mononuclear cell proliferation (37%) as well as in the production of cytokines by cultured cells (interleukin-1 (IL-1), interleukin-2 (IL-2), tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma), by 37%, 35%, 26% and 16%, respectively). All of these changes were prevented by the ingestion of a carbohydrate drink by the athletes, except that in IFN-gamma production, which was equally decreased (17%) after the second trial. The concentration of plasma glutamine, an important fuel for immune cells, was decreased in the placebo group but maintained in the group that received carbohydrate.

Carbohydrate supplementation affects positively the immune response of cyclists by avoiding or minimizing changes in plasma glutamine concentration.