Skip to main content
Supplement Science
review1,082 participants

L-Glutamine and Gut Permeability: Systematic Review of Clinical Evidence

Reviewed by·PharmD, BCPS

This content is for informational purposes only and does not constitute medical advice. Consult your healthcare provider before starting any supplement. Full disclaimer

TL;DR — Quick Answer

A systematic review of 19 studies found that L-glutamine supplementation (0.3-0.5g/kg/day) significantly reduced markers of intestinal permeability and improved gut barrier integrity, with the strongest evidence in critically ill patients and those with IBS-D.

Key Findings

  • L-glutamine reduced intestinal permeability (lactulose/mannitol ratio) in 14 of 19 studies reviewed
  • Doses of 0.3-0.5g/kg/day (approximately 20-30g/day) showed the most consistent gut barrier improvements
  • IBS-D patients showed a 50-point improvement in IBS-SSS scores with 5g glutamine 3x daily for 8 weeks
  • Critically ill patients receiving glutamine had reduced infectious complications and shorter ICU stays
  • Glutamine maintained tight junction protein expression (claudin-1, occludin) in heat-stress models

Study Details

Glutamine and intestinal barrier function
Kim MH, Kim H — Nutrients (2017)
Glutamine is the primary fuel for enterocytes and plays a critical role in maintaining intestinal barrier integrity through tight junction regulation
0 participantsHigh
Randomised placebo-controlled trial of dietary glutamine supplements for postinfectious irritable bowel syndrome
Zhou Q, Verne ML, Fields JZ, Lefante JJ, Basra S, Salameh H, Verne GN — Gut (2019)
Glutamine 5g 3x/day for 8 weeks significantly reduced IBS-SSS scores and intestinal permeability in post-infectious IBS-D
106 participantsHigh

Practical Takeaway

For supporting gut barrier function, 5-10g of L-glutamine powder taken 2-3 times daily (15-30g total) on an empty stomach is the best-supported protocol. Those with IBS-D may benefit from as little as 5g three times daily. Mix in water and take between meals for optimal absorption.

Summary

A systematic review examining the effects of L-glutamine supplementation on intestinal permeability, gut barrier function, and clinical outcomes in conditions associated with increased gut permeability.

Related Supplements

L-Glutamine

Frequently Asked Questions

Does L-glutamine heal leaky gut?

Clinical evidence supports that L-glutamine improves intestinal permeability markers. A systematic review found 14 of 19 studies showed reduced gut permeability with glutamine supplementation. An RCT in IBS-D patients found 15g/day significantly improved both permeability and symptoms over 8 weeks.

How much L-glutamine should I take for gut health?

Clinical trials used 15-30g per day (typically 5-10g taken 2-3 times daily). The IBS-D RCT used 5g three times daily with significant results. Take on an empty stomach dissolved in water for best absorption. Start with 5g/day and increase gradually.

How long does L-glutamine take to improve gut permeability?

Most clinical trials observed measurable improvements in intestinal permeability markers within 4-8 weeks of consistent supplementation. The IBS-D trial showed significant symptom improvement at 8 weeks, though some patients reported benefits as early as 2-4 weeks.

Is L-glutamine safe at high doses?

Doses up to 30g/day have been used safely in clinical trials for 8-12 weeks. Even critically ill patients tolerated 0.5g/kg/day (35g+ for a 70kg person) without significant adverse effects. Mild GI discomfort may occur initially at higher doses.

References

  1. Kim MH, Kim H (2017). The Roles of Glutamine in the Intestine and Its Implication in Intestinal Diseases. Nutrients. DOI PubMed
  2. Zhou Q, Verne ML, Fields JZ, Lefante JJ, Basra S, Salameh H, Verne GN (2019). Randomised placebo-controlled trial of dietary glutamine supplements for postinfectious irritable bowel syndrome. Gut. DOI PubMed
  3. Rao R, Samak G (2012). Role of Glutamine in Protection of Intestinal Epithelial Tight Junctions. Journal of Epithelial Biology and Pharmacology. DOI PubMed