In this guide
What is L-Glutamine?
L-glutamine is a conditionally indispensable amino acid in some physiologic stress states and the most abundant free amino acid in plasma and muscle. Those facts do not establish a retail gut-repair regimen. The WHO indispensable-amino-acid table does not set an adult dietary requirement for this ingredient; no supplement target follows. [1]
Typical L-Glutamine Research Protocols
| Source and population | Form and amount per administration | Frequency | Total exposure | Duration or window |
|---|---|---|---|---|
| Pugh 2017 · 10 recreationally active men | L-glutamine 0.25, 0.5 or 0.9 g/kg fat-free mass once | 2 hours before a 60-minute run in 30°C | One FFM-scaled dose | Acute permeability and symptom window |
| Ogden 2022 · 10 men | L-glutamine 0.3 g/kg fat-free mass once | 1 hour before exhaustive running in 40°C | One FFM-scaled dose | Acute permeability, injury and translocation |
These rows reproduce studies. Do not average their populations, forms, frequencies or durations into one regimen.
From dietary requirement to claim
Units, mixture, timing and endpoint stay attached to their source.
Should L-Glutamine be cycled?
No verified trial establishes a cycle. A review point can limit indefinite use, but it does not prove a physiological reset.
What happens when it is stopped?
No withdrawal syndrome is established. An acute or short study cannot predict persistence after stopping.
Which foods provide it?
Protein foods may supply this amino acid or its precursors, while a concentrated product creates a different exposure. No supplement target is established by the official source reviewed. [1]
Which forms and label details matter?
Trials used free L-glutamine scaled to fat-free mass. A body-weight dose, a fat-free-mass dose and a fixed scoop are not interchangeable. Preserve the denominator and one-time timing.
How should it be stored?
Follow the finished-product label, close the container and protect it from moisture and heat. Keep the lot number and discard a product with a broken seal or unexplained change.
What is L-Glutamine commonly used for?
Glutamine is marketed for gut integrity, recovery and immunity. The current exercise evidence measures permeability and injury biomarkers under heat stress; subjective GI symptoms did not consistently improve.
What does human research show?
Pugh found lower permeability markers after all three doses, with no improvement in already-low GI symptoms. [2] Ogden used 0.3 g/kg fat-free mass before a different, hotter exhaustive protocol and found worse permeability with no improvement in injury or microbial-translocation markers. [3] These small crossover studies conflict and do not establish a general gut-repair dose.
How might it act?
Glutamine is normally synthesized by the body and can become conditionally indispensable in particular stress states. It supplies fuel to cells of the intestinal lining and immune system. That role motivated exercise studies of gut permeability, but changing a permeability marker is not the same as relieving symptoms or treating gastrointestinal disease. The small heat-exercise studies produced conflicting biomarker results. [1]–[3]
What are the risks and interactions?
Large acute doses can cause GI discomfort and create substantial nitrogen exposure. Critical illness, cancer care, kidney or liver disease, pregnancy and pediatric use require specialist review; sports biomarker trials do not answer those clinical questions.
Which medicines can interact?
Product-specific interaction data are limited. Have the complete formula reviewed by a pharmacist when taking medicines, especially for neurologic, psychiatric, metabolic, kidney or liver conditions. Do not invent a universal separation interval.
Regulatory status: In the United States, supplements are not routinely approved for efficacy before sale. In Canada, check the NPN or DIN-HM and licensed label conditions. [4], [5]
What should be monitored?
Record product, lot, form, amount per administration, frequency, daily total, co-ingredients, dietary context, symptoms and intended outcome. Set a review date before starting.
Stop and seek advice for an allergic reaction, persistent vomiting, unusual weakness, confusion or another severe symptom.
What do public communities report?
Public discussions often emphasize taste, timing and felt effects while omitting lot, total diet and validated outcomes. This update did not independently recrawl or quantify those posts.
How does L-Glutamine compare?
| Option | What it supplies | Limit |
|---|---|---|
| L-Glutamine | One defined amino acid | Does not replace complete protein |
| EAAs | All nine indispensable amino acids | Formula varies |
| BCAAs | Leucine, isoleucine and valine | Six EAAs are absent |
| Complete protein | All EAAs in a protein matrix | Portion and digestibility vary |
Common questions about L-Glutamine
Does glutamine repair a leaky gut?
The two verified heat-exercise studies conflicted on permeability and did not establish treatment for a diagnosed intestinal disorder.
Why use fat-free mass rather than body weight?
Those trials scaled the dose to fat-free mass. Changing the denominator changes the exposure.
Did lower GI permeability improve symptoms?
No. In the positive biomarker study, GI symptoms were already low and did not improve.
Why did the second heat study differ?
It used a hotter exhaustive protocol, a different timing and 0.3 g/kg fat-free mass; permeability worsened rather than improved.
Can sports trials guide critical-illness or cancer care?
No. Those are separate clinical settings with different risk and evidence.
What should I track?
Record free L-glutamine, fat-free-mass denominator, exact one-time dose, pre-exercise interval, heat load, GI symptoms and review date.
Glossary
Plain terms for interpreting the evidence.
- Indispensable amino acid
- An amino acid the diet must provide.
- Dietary requirement
- Total required intake; not a supplement dose.
- Amount per administration
- Amount consumed at one time, distinct from daily total.
- NOAEL
- Highest tested level without an observed adverse effect in one study; not automatically a UL.
- UL
- Tolerable Upper Intake Level established by an authority.
- Biomarker
- Biological measure that is not necessarily a felt or clinical benefit.
How this guide was researched
The complete WHO report, accessible primary human studies and live NCBI metadata were read on October 9, 2026. Titles, authors, journals, DOI, PMID, available PMCID and CommentsCorrections were checked. Open full text supplied methods details; an unreported frequency was not guessed. [1], [2], [3], [4], [5]
How this guide was made
Research and drafting were AI-assisted. This draft awaits Doserly editorial review and independent clinical review. See the editorial policy.
Explore the sources
Sources preserve form, dose, frequency, population, duration and outcome.
Showing 5 sources
- 01
Protein and amino acid requirements in human nutrition: report of a joint WHO/FAO/UNU expert consultation ↗
Official expert report
Current primary source and identity checked; limitations are retained in the text.
Detail: Glutamine is not assigned an adult indispensable-amino-acid requirement in Table 49; absence of a target is not proof of unlimited safety.
- 02
Glutamine supplementation reduces markers of intestinal permeability during running in the heat in a dose-dependent manner. ↗
Randomized crossover study
Current primary source and identity checked; limitations are retained in the text.
Detail: 0.25–0.9 g/kg fat-free mass once, two hours before running in heat.
- 03
Acute L-glutamine supplementation does not improve gastrointestinal permeability, injury or microbial translocation in response to exhaustive high intensity exertional-heat stress. ↗
Randomized crossover study
Current primary source and identity checked; limitations are retained in the text.
Detail: 0.3 g/kg fat-free mass once, one hour before exhaustive exertional heat stress; permeability worsened.
- 04
Questions and Answers on Dietary Supplements ↗
U.S. regulatory overview
Current primary source and identity checked; limitations are retained in the text.
Detail: Dietary supplements are not routinely FDA-approved for efficacy before sale.
- 05
Product Licensing ↗
Canadian licensing overview
Current primary source and identity checked; limitations are retained in the text.
Detail: Canadian authorization attaches to the licensed finished product and label conditions.
No matching sources
Try a different term or show the full list.