Is L-glutamine worth it?
L-glutamine has a real signal in a narrow post-infectious IBS-D trial, but that is not the same as proof for broad gut-repair or leaky-gut marketing. Most healthy buyers already make and eat glutamine. The evidence supports a clinical niche, not a default digestive stack.
The call
A randomized placebo-controlled Gut trial reported large symptom improvements with oral glutamine in adults who developed IBS-D with increased intestinal permeability after enteric infection. That is meaningful, but it is also highly phenotype-specific and the authors called for larger validation trials. General digestive buyers usually do not know whether they have that post-infectious permeability pattern, and broad gut-lining claims often cite mechanism instead of outcomes. Mixed evidence plus overbroad marketing lands as a skip for routine use.
Safety
L-glutamine can cause constipation, nausea, headache, abdominal pain, cough, and body aches. Avoid casual supplementation with severe liver disease, hepatic encephalopathy risk, significant kidney disease, pregnancy, breastfeeding, active cancer treatment, seizure disorders, bipolar or mania risk, or complex prescription regimens unless a clinician clears it. People with sickle cell disease should distinguish prescription L-glutamine use from over-the-counter digestive use. Stop if abdominal symptoms worsen, confusion develops, or new neurological symptoms appear.
Dose that matters: No general gut-repair dose recommended. The notable post-infectious IBS-D trial used 5 g three times daily for 8 weeks in adults with diarrhea-predominant symptoms and increased intestinal permeability after infection; that phenotype should be clinician-matched rather than self-diagnosed.
Sources
Tier 2 · evidence synthesis · Reviewed by the Stack-kit desk