L-Glutamine
L-Glutamine
TL;DR
L-glutamine is the most abundant amino acid and the main fuel for gut and immune cells. Conditionally essential in illness; benefits in healthy people are modest.
Ideal For
- People with IBS and suspected increased intestinal permeability
- Those recovering from major surgery, burns or trauma, under medical care
- Endurance athletes in heavy training blocks
- People with sickle cell disease, where it is an approved therapy
- Those undergoing chemotherapy with mucositis, with oncology input
Avoid If
- You have cirrhosis or hepatic encephalopathy
- You have significant kidney disease
- You have a history of seizures
- You expect it to build muscle in healthy training
Frequently Asked Questions
Overview
Glutamine is the most abundant free amino acid in human plasma and muscle, and the body synthesises it in large quantities from glutamate and branched-chain amino acids. Under normal conditions supplementation adds little, which is why the amino acid is classed as conditionally rather than truly essential. Under catabolic stress — major burns, sepsis, trauma, surgery, prolonged endurance work — demand outpaces synthesis and plasma levels fall, which is where the useful evidence sits.
Two tissues consume it heavily. Enterocytes use glutamine as their preferred fuel, and it supports tight junction protein expression, which underpins its use in intestinal permeability research. Lymphocytes and macrophages also rely on it during proliferation, which is why the post-exercise immune suppression literature examined it, though the results there are weaker than the marketing suggests.
Clinically, glutamine has genuine roles: parenteral supplementation in critical illness and burns has trial support, and oral glutamine is an approved treatment for sickle cell disease to reduce crises. In IBS with increased permeability, one randomised trial at 15 g/day found meaningful symptom improvement. For muscle building in healthy trained people, the evidence is essentially negative — glutamine does not increase strength or lean mass.
How It Works
- Primary metabolic fuel for enterocytes, supporting mucosal turnover
- Substrate for glutathione synthesis, contributing to antioxidant defence
- Supports tight junction protein expression and intestinal barrier function
- Fuels lymphocyte and macrophage proliferation during immune activation
- Acts as a nitrogen shuttle between muscle and other tissues
- Serves as a precursor for glutamate and GABA in the brain
Quick Facts
- Primary fuel for intestinal cells
- Supports gut barrier function and leaky gut
- Important for immune system function
- Aids muscle recovery and glycogen storage
- Conditionally essential during stress or illness
Benefits & Outcomes
Wound Healing
Glutamine matters in burns and critical illness rather than routine wounds.
Constipation Relief
Glutamine is used for intestinal barrier support, not motility, and has no meaningful constipation evidence.
Post-Workout Recovery
Glutamine does not improve recovery, soreness or performance in healthy trained people.
T-Cell Function Enhancement
Glutamine matters for lymphocytes under severe catabolic stress, not in healthy people.
Gut Barrier Integrity
Glutamine plausibly supports intestinal barrier function, with best evidence in critical illness and specific IBS subgroups.
Immune Function
Glutamine matters in catabolic illness where plasma levels fall; routine supplementation in healthy people shows no immune benefit.
Heartburn Relief
Mechanistically appealing for mucosal repair, essentially untested for reflux.
Health Concerns Addressed
Leaky Gut Syndrome
Glutamine is the primary fuel for enterocytes and supports intestinal barrier integrity, with good evidence in critical illness and mucosal injury. For general gut symptoms attributed to leaky gut, evidence is limited and should not replace diagnostic workup.
IBS (Irritable Bowel Syndrome)
One promising trial in post-infectious IBS with increased intestinal permeability has not yet been replicated.
SIBO (Small Intestinal Bacterial Overgrowth)
No evidence supports glutamine as a SIBO treatment; it targets barrier function rather than bacterial overgrowth.
Supporting Research9 studies
A randomized trial of glutamine and antioxidants in critically ill patients (REDOXS)
Heyland D, Muscedere J, Wischmeyer PE +3 more
Early provision of glutamine in critically ill patients with multiorgan failure was associated with an increase in mortality.
Phase III double-blind study of glutamine versus placebo for the prevention of acute diarrhea in patients receiving pelvic radiation therapy
Kozelsky TF
There is no evidence of a beneficial effect of glutamine during pelvic RT.
Glutamine supplementation and gut barrier and mucosal immune function: a systematic review
Perna S, Alalwan TA, Alaali Z +3 more
Glutamine improved intestinal permeability markers in catabolic and stressed patients
Effect of administration of β-hydroxy-β-methyl butyrate-enriched formula after liver transplantation: A pilot randomized controlled trial
Kamo N, Kaido T, Uozumi R +1 more
Patients in the HMB group received two packs of HMB-rich nutrients per day, which contained calcium-HMB (1500 mg), l-arginine (7000 mg), and l -glutamine (7000 mg) per pack
Glutamine supplementation in critically ill and surgical patients: an updated meta-analysis of randomised trials
Tao KM, Li XQ, Yang LQ +3 more
Glutamine supplementation showed no effect on mortality but was associated with a reduction in infectious complications and length of hospital stay.
Randomised clinical trial: oral glutamine reduces intestinal permeability and IBS symptoms in postinfectious IBS with diarrhoea
Zhou Q, Verne ML, Fields JZ +4 more
Oral dietary glutamine supplements dramatically reduced all major IBS-related endpoints in patients with IBS-D and increased intestinal permeability.
Glutamine supplementation and exercise-induced immune and gut permeability changes: a systematic review
Ramezani Ahmadi A, Rayyani E, Bahreini M +1 more
Glutamine supplementation attenuated exercise-induced increases in intestinal permeability, while effects on immune outcomes were inconsistent.
Glutamine for induction of remission in Crohn's disease (Cochrane review)
Yamamoto T, Shimoyama T, Bamba T
There is no evidence from the available randomised trials that glutamine supplementation is effective for induction of remission in Crohn's disease.
Effects of oral glutamine supplementation on lean body mass and strength: a systematic review of resistance-training trials
Candow DG, Chilibeck PD, Burke DG +2 more
Glutamine supplementation during resistance training had no significant effect on muscle performance, body composition or muscle protein degradation.
Safety Information
Potential Side Effects
Very well tolerated at typical doses. Bloating, nausea or loose stools at high single doses. The important cautions are hepatic and renal rather than dose-related toxicity.
Contraindications
Avoid in hepatic encephalopathy and advanced liver disease, where glutamine metabolism increases ammonia load. Use caution in significant renal impairment and in people with seizure disorders given glutamate precursor activity.
Drug Interactions
- Anticonvulsants — theoretical reduction in efficacy through glutamate pathways
- Lactulose — glutamine may counteract its ammonia-lowering effect
- Chemotherapy — discuss with oncology, since tumour glutamine metabolism is an active research area
Pregnancy & Breastfeeding
Pregnancy: insufficient_data
Breastfeeding: insufficient_data
Dosage Guidelines
Dosage Used in Studies
Consult healthcare provider
Best Time to Take
Split into two or three doses across the day
Best Form
L-glutamine free-form powder for oral use; alanyl-glutamine where stability in solution matters
Forms Compared
L-glutamine free-form powder
Alanyl-glutamine dipeptide
Capsules
Food & Timing
Between meals on an empty stomach for gut-targeted use; with food is fine otherwise
Medical Disclaimer
The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.
Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.