Supertraining

European Journal of Clinical Nutrition (2007) 61, 443–460.

Nutritional modulation of exercise-induced immunodepression in
athletes: a systematic review and meta-analysis.  A Moreira, R A
Kekkonen, L Delgado, J Fonseca, R Korpela and T Haahtela.

Background: Heavy exercise induces marked immunodepression that is
multifactorial in origin. Nutrition can modulate normal immune
function.

Objective: To assess the efficacy of nutritional supplements in
exercise-induced immunodepression in athletes.

Design: Systematic review.

Review methods:
Randomised and/or controlled trials of athletes undertaking
nutritional supplements to minimise the immunodepression after
exercise were retrieved. The primary outcome measure was incidence of
upper respiratory tract (URT) illness symptoms after exercise, and
secondary outcomes included cortisol, cell counts, plasma cytokine
concentration, cell proliferative response, oxidative burst, natural
killer cell activity and immunoglobulins. When data were available for
a pooled estimate of the effect of intervention, meta-analyses were
conducted for direct comparisons.

Results:
Forty-five studies were included (1603 subjects). The studies were
heterogeneous in terms of exercise interventions, selection of
athletes, settings and outcomes. The overall methodological quality of
most of the trials was poor. Twenty studies addressed carbohydrate
supplementation, eight glutamine, 13 vitamin C and four others
interventions. Three trials assessed the effect of intervention on
prevention of URT infections. The pooled rate ratio for URT infections
after vitamin C supplementation against placebo was 0.49 (0.34–0.71).
Carbohydrate supplementation attenuated the increase in cortisol and
neutrophils after exercise; vitamin C attenuated the decrease in
lymphocytes after exercise. No other interventions had significant or
consistent effect on any of the studied outcomes.

Conclusions:
Although the prevention of URT infections by vitamin C was supported
by two trials, further studies are needed. The available evidence
failed to support a role for other nutritional supplements in
preventing exercise-induced immune suppression. Larger trials with
clinically relevant and uniform end points are necessary to clarify
the role of these nutritional interventions.
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Krista Scott-Dixon
Toronto, ON
[EMAIL PROTECTED]


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