L-Glutamine

What Is L-Glutamine?

L-Glutamine is the most abundant free amino acid in the body and a conditionally essential nutrient — a primary fuel for rapidly dividing cells lining the gut and for immune cells. It is taken as a supplement mainly for gut-lining (“leaky gut”) support and for exercise recovery. The evidence is context-dependent: it is best supported in specific clinical settings (post-infectious IBS, critical illness) and weaker as a general recovery aid in healthy, well-fed athletes, for whom glutamine is normally plentiful.

Evidence

An 8-week randomised, placebo-controlled trial in adults with post-infectious IBS and increased intestinal permeability found that glutamine (5 g three times daily) markedly reduced symptom severity versus placebo and normalised intestinal permeability ^{1Reference 1Zhou Q et al. · 2019RCTRandomised placebo-controlled trial of dietary glutamine supplements for postinfectious irritable bowel syndrome — randomised controlled trialView study →}. A 2024 systematic review and meta-analysis of glutamine and gut permeability concluded that, overall, supplementation did not significantly change intestinal permeability, but that a benefit appeared in a subgroup using higher doses (over ~30 g/day) ^{2Reference 2Abbasi F et al. · 2024Meta-analysisA systematic review and meta-analysis of clinical trials on the effects of glutamine supplementation on gut permeability in adults — meta-analysisView study →} — i.e. the effect is dose- and context-dependent rather than universal. The broader “heals the gut lining” and “boosts recovery” claims are commonly made; the trial support is real but narrower than the marketing implies.

Dosage & Safety

The post-infectious IBS trial used 5 g three times daily; other research uses a wide range (this is the studied range, not a personal recommendation). Glutamine is well tolerated in healthy adults. It carries a nitrogen load, so caution is warranted in people with significant liver or kidney disease, and it should be used carefully by anyone on medications affected by amino-acid or ammonia handling. Specific drug interactions and pregnancy safety were not assessed in this pass.

References

1. Zhou Q, Verne ML, Fields JZ, et al. (2019). Randomised placebo-controlled trial of dietary glutamine supplements for postinfectious irritable bowel syndrome — randomised controlled trial. Gut. https://pubmed.ncbi.nlm.nih.gov/30244201/
2. Abbasi F, et al. (2024). A systematic review and meta-analysis of clinical trials on the effects of glutamine supplementation on gut permeability in adults — meta-analysis. Amino Acids. https://doi.org/10.1007/s00726-024-03420-7