Effects of L-glutamine supplementation on mucosal immunity, hormonal status, and well-being in combat-sport athletes: a randomized controlled trial
The study discusses the effects of prolonged physical exertion on athletes, especially those in combat sports, who are exposed to high risks of upper respiratory tract infections (URTI) due to a combination of intense training, rapid weight reduction, and close contact during training and competition.
Athletes in these disciplines are particularly vulnerable to upper respiratory tract infections due to suppressed mucosal immunity and increased pathogen exposure. Various biological markers are also discussed, including salivary immunoglobulin A (SIgA), nitric oxide (NO), and hormone levels of testosterone (T) and cortisol (C), which are influenced by intense training and can be indicators of athletes’ training status and recovery.
The article highlights the importance of glutamine as a fundamental substance for the immune system, emphasizing how its deficiency can compromise immunity and lead to increased susceptibility to infections.
The purpose of this study was to evaluate whether three weeks of L-glutamine supplementation could benefit mucosal immunity and hormonal status in combat-sport athletes, as well as rates of upper respiratory tract infections (URTI) and subjective feelings of well-being after intensive training.
Twenty-one combat-sport athletes were recruited from the National Taiwan University of Sport for this study. After intensive training, two groups of participants were instructed to consume 0.3 g/kg body weight of L-glutamine (GLU group) or maltodextrin (PLA group) in powder form with drinking water at the same time each day for 3 weeks in a randomized design.
Saliva samples were collected to measure immunoglobulin A (IgA), nitric oxide (NO), testosterone (T), and cortisol (C) before and after three weeks of supplementation; additionally, Hooper index questionnaires were completed for well-being assessment. The incidence and duration of URTI were recorded using a health checklist for the entire study period.
L-glutamine supplementation significantly increased concentrations of IgA and NO in saliva; furthermore, the incidence of URTI was significantly reduced. Regarding hormones, T concentration significantly decreased in the PLA group, while C concentration significantly increased, resulting in a significant decrease in the T/C ratio. In contrast, the GLU group showed a significant increase in the T/C ratio, while mood scores on the Hooper index questionnaire were higher in the PLA group.
Three weeks of L-glutamine supplementation after intensive training enhanced mucosal immunity, improved hormonal status, and reduced the rate of upper respiratory tract infections in combat-sport athletes, while feelings of well-being were also enhanced. Therefore, L-glutamine would be advantageous for athletic performance and recovery.
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Source: Lu TL, Zheng AC, Suzuki K, Lu CC, Wang CY, Fang SH. Supplementation of L-glutamine enhanced mucosal immunity and improved hormonal status of combat-sport athletes. J Int Soc Sports Nutr. 2024 Dec;21(1):2300259. doi: 10.1080/15502783.2023.2300259. Epub 2024 Jan 9. PMID: 38193521; PMCID: PMC10783826.
