The role of nutrition is central to the development and modulation of the immune system. The importance of nutrition has been made clear by the burgeoning field of sports medicine. It appears the immune system is enhanced by moderate to severe exercise, although many components of the immune response exhibit adverse change for a period of from 3 to 72 hours after prolonged intense exertion. This "window of opportunity" for opportunistic bacterial and viral infections seems to be increased for "elite" athletes that are more prone to over-train. The elements of the immune response most affected by the strenuous activity that leads to the impairment of the immune system are lymphocyte concentrations, depressed natural killer activity, and elevated levels of IgA in the saliva.

The possible basis for this prolonged immunosuppression may include reduced plasma glutamine concentrations, altered plasma glucose levels, and proliferation of neutrophils and...