Evidence Level
Glutamine is a widely used yet often overhyped supplement in sports nutrition. For muscle growth, evidence indicates that glutamine does not enhance muscle protein synthesis or strength gains in well-fed individuals consuming adequate protein (Candow et al., 2001). However, its role in immune and gut health is supported by research.
Intense prolonged exercise depletes plasma glutamine by 10-30%, potentially creating an "open window" of immune vulnerability. Castell et al. (1996) demonstrated that supplementation reduced post-exercise infections. For gut health, glutamine serves as the primary fuel for enterocytes and may help maintain intestinal integrity.
A systematic review and meta-analysis by Abbasi et al. (2024) of 10 clinical trials involving 352 participants found no significant effect of glutamine supplementation on intestinal permeability overall. However, a reduction in permeability was observed with doses exceeding 30g/day. In the context of critical illness and burns, several studies have explored glutamine's benefits. Tao et al. (2024) reviewed 22 trials involving 2170 participants, concluding that glutamine supplementation shortened hospital stay, improved wound healing, and reduced wound infection in burn patients. Similarly, Yue et al. (2024) analyzed six RCTs with 1398 patients, finding that enteral glutamine may shorten hospital stay and lower wound infection risk in severe burn patients, though it did not significantly reduce mortality or infectious morbidities.
Overall, while glutamine does not enhance muscle growth in well-fed individuals, its role in supporting immune function and gut health is supported by evidence. Practical recommendations include considering glutamine during heavy endurance training or for managing exercise-induced gastrointestinal issues.