L-glutamine
Gut
Amino acid promoted for intestinal lining repair.
What it is
The most abundant amino acid in your body and a fixture of gut-health marketing. It has genuine clinical uses in serious illness, and very little evidence for the healthy person buying it for "leaky gut" or muscle recovery.
How it works
Glutamine is the preferred fuel for intestinal cells and immune cells, which is why it matters in trauma, burns and critical illness where the body burns through it. In a healthy, well-fed person, the body makes plenty, glutamine is only "conditionally essential", and that condition is severe physiological stress, not a normal training week.
Which form to buy
Cheap, tasteless, dissolves easily.
The default if you use it.
Studied amounts run several grams, so capsule counts get silly.
Impractical for meaningful amounts.
Usually well under the amounts used in research.
Decorative quantities.
What it actually does, graded
ESPEN recommends AGAINST added enteral glutamine in general ICU patients, and controlled trials in short-bowel syndrome did not show benefit. Only narrow burn/trauma protocols retain conditional support, themselves challenged by a large null trial.
One notable trial in post-infectious IBS with diarrhoea showed benefit; not broadly replicated.
The dominant marketing claim, and "leaky gut" is not a recognized diagnosis in the way supplement pages use it.
Repeatedly tested in resistance-training contexts and repeatedly null.
Some older endurance-athlete research, largely superseded and inconsistent.
Pros and cons
- Cheap and very well tolerated
- Narrow, supervised clinical protocols retain conditional support
- Almost every consumer claim outruns the evidence badly
- Healthy people synthesize plenty already
- The most-sold reason to take it (leaky gut) is the least supported
What to expect
- In healthy people: honestly nothing measurable, per the trials.
- The clinical uses were measured in hospital settings over days to weeks.
Interactions
Is it for you?
- A specific condition your clinician is actively managing with it
- Post-infectious IBS with diarrhoea, as a low-risk experiment with modest expectations
- You are buying it for leaky gut, muscle recovery, or general gut health, the evidence is not there
Who should avoid it
- Anyone with liver disease and encephalopathy
- Nobody else categorically, the seizure concern above is theoretical, not demonstrated
Research on this supplement
Papers about this supplement, not proof of the claims above. A title says what was studied, which is sometimes a negative result or a different question entirely.
- Systematic Review of l-glutamine for Prevention of Vaso-occlusive Pain Crisis in Patients with Sickle Cell Disease
- Dissecting L-glutamine metabolism in acute myeloid leukemia: single-cell insights and therapeutic implications
- L-glutamine sensitizes Gram-positive-resistant bacteria to gentamicin killing
What the evidence says
Real evidence in clinical settings (burns, critical illness, some IBS subgroups). Evidence for "leaky gut" in otherwise healthy people is not there.
What studies used
5 g daily is common; gut trials use more. Any time.
Reported from published studies and product labelling — a record of what was used in research, not a recommendation. What is right for you is a conversation with a clinician.
Evidence base
established literature
Large human evidence base: several phase 3 or 4 trial reports, plus multiple meta-analyses or systematic reviews.
This letter measures how much human research exists, not whether it works for you — the tier above (Limited) is the read on quality.
Research (12)
- L-Glutamine2012
- L-glutamine for sickle cell disease: Knight or pawn?Exp Biol Med (Maywood) · 2020
- L-glutamine for sickle cell disease: more than reducing redoxAnn Hematol · 2022
- L-Glutamine-, peptidyl- and protein-glutaminases: structural features and applications in the food industryWorld J Microbiol Biotechnol · 2022
- l-Glutamine for sickle cell anemia: more questions than answersBlood · 2018
- L-glutamine sensitizes Gram-positive-resistant bacteria to gentamicin killingMicrobiol Spectr · 2023
- An L-Glutamine Transporter Isoform for Neurogenesis Facilitated by L-TheanineNeurochem Res · 2017
- Dissecting L-glutamine metabolism in acute myeloid leukemia: single-cell insights and therapeutic implicationsJ Transl Med · 2024
- L-Glutamine in sickle cell diseaseDrugs Today (Barc) · 2020
- The Emerging Role of l-Glutamine in Cardiovascular Health and DiseaseNutrients · 2019
- L-Glutamine is better for treatment than prevention in exhaustive exerciseFront Physiol · 2023
- The vaso-occlusive pain crisis in sickle cell disease: Definition, pathophysiology, and managementEur J Haematol · 2020
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