Effets d’une supplémentation en glutamine chez des nageurs de haut niveau

Elite athletes are a very specific population characterized by a particularly rigorous and strenuous training schedule, numerous trips abroad, and the experience of psychological stress. Nutrition is undoubtedly a sizeable element that can have a direct impact on performance. Optimal periodization of nutritional intakes and the use of ergogenic aids is of paramount importance. Given that this group is represented by a relatively small pool of subjects and its participation in research projects involves many methodological challenges, very few studies have been conducted amongst this type of athlete. Intense training executed at a chronic level is linked to a decrease in plasma reserves of glutamine. Glutamine has many functions, including that of acting as a major energy substrate for enterocytes and immune cells. Studies paradoxically observed an increase in the incidence of respiratory tract infections (URTI) as well as gastrointestinal disorders (GD) in elite athletes. In addition, they showed that glutamine plays an anti-inflammatory role and, as it is involved in the secretion of heat shock proteins (HSP), essentially serves as a source of protection for the body. This study was a cross-sectional, randomized, crossover and single-blinded controlled trial with a placebo (n = 11, 3 dropouts). Data collection took place during two distinct periods of the swimming competition season (phases A and B). Each participant received either the glutamine supplement or placebo during phase A and vice versa during phase B. The initial hypothesis stipulated that supplements with glutamine (0.6 g/kg fat-free mass) administered amongst elite swimmers before (ten days), during (three days), and after (five days) a competition would limit the plasma glutamine and salivary immunoglobulin A (IgA) drop caused by the competition. Also, it was assumed that supplementation would limit the presence of inflammation (C-reactive protein and haptoglobin) while stimulating the production of HSP- 72, reducing URTI and GD incidence and positively affecting indicators associated with recovery (assessed by a questionnaire: the RESTQ-Sport). As a second hypothesis, it was stipulated that the competition would have a physiological impact on the athletes. v The results of the trial, derived from traditional statistics and exploratory unsupervised multivariate statistical analyses (principal component analysis), showed no associated benefits for the athletes who received the glutamine supplement. No significant differences were observed between experimental groups in regards to concentrations of plasma glutamine, salivary IgA, CRP, haptoglobin and HSP-72. The RESTQ-Sport values were slightly influenced by the supplement, however. Although the sum of eight URTI severity symptoms appeared reduced in the group who received the upplement, very few athletes had contracted an actual infection, according to the definition used. Within the supplemented group, the incidence of gastrointestinal disorders was only significantly reduced in Phase B of the project. Lastly, with regards to the impacts of competition, no significant differences were compiled before and after competition measures. In summary, chronic supplementation of glutamine administered before, during, and after a swimming competition does not appear to have any benefits on the supplemented group of swimmers. However, given the presence of several methodological limitations beyond the study’s control and stemming from the nature of competitive sports, it would be incorrect to assert the ineffectiveness of glutamine supplementation on elite swimmers. These challenges further emphasize the complexity associated with the study of this very specific group. Thus, in subsequent research projects, verifying the effects of glutamine supplementation on an elite group of athletes will continue to be of the utmost importance. Given the complexity of obtaining a large homogenous sample size, increasing the frequency of measures will be necessary in order to compensate for large intra- and inter-individual variability in responses.

Keyphrases: inflammation, Glutamine supplementation, plasma glutamine, immunity, inflammation, swimming