A systematic review and meta-analysis of clinical trials on the effects of glutamine supplementation on gut permeability in adults

The gastrointestinal tract's epithelial barrier plays a crucial role in maintaining health. This study aims to investigate the impact of glutamine supplementation on intestinal permeability, considering its importance for immune function and nutrient absorption. The study adhered to the PRISMA protocol for systematic reviews and meta-analyses. A systematic search was performed in four databases (PubMed, Scopus, Web of Science, and Google Scholar) until April 2023 to identify clinical trials on glutamine supplementation and gastrointestinal permeability. Eligibility criteria included randomized placebo-controlled trials measuring gut permeability post-glutamine supplementation. Studies were included regardless of language or publication date. Data extraction involved study characteristics, intervention details, and outcomes. Quality assessment was performed using the Cochrane tool, and statistical analysis utilized mean differences and standard deviations with a random effects model. Subgroup analysis was conducted to explore heterogeneity. The systematic review and meta-analysis included 10 studies from 1998 to 2014 with 352 participants. A total of 216 patients were enrolled in the intervention group, and 212 in the control group. The mean participant age was 46.52 years. The participants had different types of diseases in terms of their health status. Overall, glutamine supplementation did not significantly affect intestinal permeability (WMD: -0.00, 95% CI -0.04, 0.03). Subgroup analysis showed a significant reduction in intestinal permeability with doses over 30g/day (WMD: -0.01, 95% CI -0.10, -0.08). The glutamine supplements were administered orally in all included studies. The meta-analysis demonstrated a significant reduction in intestinal permeability with glutamine supplementation exceeding 30 mg/day for durations of less than 2 weeks. Further investigations with varying dosages and patient populations are warranted to enhance understanding and recommendations regarding glutamine supplementation's effects on gut permeability.