The study – a systematic review and meta-analysis of clinical trials – evaluated the impact of glutamine supplementation on intestinal permeability, which is critical for immune function and nutrient absorption.
“[We] found that short time (less than 2 weeks) glutamine supplementation in higher dosages (> 30 mg/day) had significant reductive effect on gut permeability,” wrote researchers in Springer Nature Link.
The gastrointestinal (GI) tract is lined by a single layer of epithelial cells, which act as a protective barrier against microbial invasion.
Increased intestinal permeability, due to leakage between epithelial cells, allows harmful toxins can enter the bloodstream, triggering immune responses, inflammation and impaired nutrient absorption.
Glutamine, a non-essential amino acid, is vital for gut health. It supports the growth and repair of intestinal cells and serves as an energy source for rapidly dividing cells, making it essential during infections, injuries, or metabolic stress.
However, previous findings regarding the impact of glutamine on gut permeability have been inconsistent. Therefore, this study aims to evaluate the effects of glutamine supplementation on human gastrointestinal permeability.
The study
A systematic search was performed in PubMed, Scopus, Web of Science, and Google Scholar until April 2023 to identify clinical trials on glutamine supplementation and gastrointestinal permeability.
These included 12 randomised placebo-controlled trials measuring gut permeability post-glutamine supplementation, published between 1998 to 2014 with 352 participants.
The mean participant age was 46.52 years. They were diagnosed with conditions that included Crohn’s Disease, metastatic cancer, and HIV-positive.
Participants in the intervention groups consumed varying glutamine doses, such as 4g/day, 7g three times daily, or 0.5g per kilogram of ideal body weight daily.
Control groups either ingested placebos like whey protein, received supportive care, or did not receive glutamine supplementation.
Results
To determine the effects of glutamine on intestinal permeability, researchers calculated the weighted mean difference (WMD) values, which indicates the differences between treatment groups in the ‘before’ and ‘after’ overall values after intervention.
In this study, the WMD values reflect how glutamine supplementation affects intestinal permeability – negative WMD values indicate a reduction in intestinal permeability, while positive values indicate an increase.
Overall, the analysis across all 12 studies showed a WMD of −0.00, indicating that glutamine supplementation did not significantly affect intestinal permeability.
However, subgroup analysis revealed there was a significant reduction in intestinal permeability with doses over 30g/day, with a WMD of −0.01.
Dosages with less than 30g/day did not yield any significant effects and had a WMD of 0.0.
Additionally, interventions lasting less than two weeks significantly improved gut permeability, whereas those extending beyond four weeks showed no effect.
For example, short-term interventions of less than two weeks showed a WMD of −0.03, indicating a significant reduction in intestinal permeability.
Long-term interventions lasting four weeks or more showed no clear effect on intestinal permeability – the WMD was −0.02, but the range of possible results, or confidence interval, stretched from −0.02 to 0.06, indicating that the findings could have occurred by chance.
“Current meta-analysis showed no significant effect of glutamine supplementation on gut permeability. However, more than 30 mg/day glutamine significantly reduced intestinal permeability.
“[The] meta-analysis demonstrated a significant reduction in intestinal permeability with glutamine supplementation exceeding 30 mg/day for durations of less than 2 weeks,” said researchers.
Further investigations with varying dosages and patient populations are warranted to enhance understanding and recommendations regarding glutamine supplementation’s effects on gut permeability.
“It seems that more studies with different dosages of glutamine in different durations are required to reach the best recommendation for this supplementation. In addition, [further] studies need to be conducted on different populations and patients to prepare suitable guidelines for glutamine supplementation in those patients,” concluded researchers.
Source: Springer Nature Link
DOI: 10.1007/s00726-024-03420-7
“A systematic review and meta-analysis of clinical trials on the effects of glutamine supplementation on gut permeability in adults”
Authors: Fatemeh Abbasi, Mohammad Mehdi Haghighat Lari et al.
