Immunosuppression in athletes involved in heavy training is undoubtedly multifactorial
in origin. Training and competitive surroundings may increase the athlete's exposure
to pathogens and provide optimal conditions for pathogen transmission. Heavy prolonged
exertion is associated with numerous hormonal and biochemical changes, many of which
potentially have detrimental effects on immune function. Furthermore, improper nutrition
can compound the negative influence of heavy exertion on immunocompetence. An athlete
exercising in a carbohydrate-depleted state experiences larger increases in circulating
stress hormones and a greater perturbation of several immune function indices. The
poor nutritional status of some athletes may predispose them to immunosuppression.
For example, dietary deficiencies of protein and specific micronutrients have long
been associated with immune dysfunction. An adequate intake of iron, zinc and B vitamins
is particularly important but the dangers of over-supplementation should also be emphasized;
many micronutrients given in quantities beyond a certain threshold will in fact reduce
immune responses and may have other toxic effects that are detrimental to health.
Although it is impossible to counter the effects of all of the factors that contribute
to exercise-induced immunosuppression, it has been shown to be possible to minimize
the effects of many factors. Athletes can help themselves by eating a well-balanced
diet that includes adequate protein and carbohydrate, sufficient to meet their energy
requirements. This will ensure a more than adequate intake of trace elements without
the need for special supplements. Consuming carbohydrate (but not glutamine) during
exercise attenuates rises in stress hormones such as cortisol and appears to limit
the degree of exercise-induced immunosuppression. By adopting sound nutritional practice,
reducing other life stresses, maintaining good hygiene, obtaining adequate rest and
spacing prolonged training sessions and competition as far apart as possible, athletes
can reduce their risk of infection.
Exercise, nutrition, immune, leukocytes, macronutrients, micronutrients.
