Amino Acids & Proteins

L-Glutamine

Also known as: Glutamine, L-glutamine powder

The most abundant amino acid in the body — a hospital staple and a popular gut-health supplement with mixed exercise evidence.

By IngredientWiki Editorial Team
Fact-checked by IngredientWiki Editorial Team
Updated 2026-09-26
2 min read

In short

L-glutamine is the most abundant free amino acid in the body, serving as the preferred fuel for rapidly dividing cells — immune cells and the cells lining the gut. In hospitals, glutamine is used in medical nutrition for trauma and burns. As a supplement, its evidence splits by goal: modest support for gut-lining health and recovery from intense training, but little benefit for muscle growth in people eating adequate protein.

Most abundant free amino acid in blood and muscle
Primary fuel for immune cells and intestinal lining cells
Medical use: trauma, burns, and critical-care nutrition
Supplement doses: 5–30 g daily

What is L-Glutamine?

Glutamine is the body's most plentiful amino acid, and its abundance reflects its workload: it feeds the immune system, powers intestinal cells, buffers acid, and shuttles nitrogen between tissues. In health, the body synthesizes all it needs — which is the key to understanding supplement results. Glutamine shines where demand outpaces supply (severe illness, burns) and offers modest, context-dependent benefits for athletes and gut health, while doing little for muscle growth itself.

Where it comes from

Natural sources

Protein foods: beef, chicken, fish, eggs, dairy
Beans, tofu, and cabbage family vegetables
Synthesized endogenously from glutamate in muscle

How it's made

Supplemental glutamine is produced by fermentation; powders dissolve easily and are nearly tasteless.

What it does in products

Benefits

Critical illness and burns (medical nutrition)

strong evidence

Glutamine is standard in specialized hospital nutrition for trauma and burn patients, reducing infection rates in several trials — a medical, not self-treatment, context.

Gut lining support

moderate evidence

Glutamine helps maintain intestinal barrier integrity, and small trials suggest reduced gut permeability after intense exercise or in IBS — promising, though the clinical significance is still debated.

Post-exercise recovery and immunity

moderate evidence

Some studies in endurance athletes find glutamine reduces post-marathon infection rates and muscle soreness — benefits are modest and mostly in heavily trained athletes.

Muscle growth

strong evidence

Contrary to bodybuilding-era marketing, glutamine supplementation does not increase muscle mass or strength — total protein intake is what matters.

Side effects & safety

Generally very well tolerated (rare)Doses up to 30 g daily appear safe in trials.

Stomach upset at very high single doses (rare)Split doses above 10 g.

Safety considerations

Limited pregnancy data at supplement doses; food and medical-nutrition uses are established.
May reduce the effectiveness of certain anti-seizure medications (lacosamide) — theoretical, but coordinate with a neurologist.
Not for: Severe liver or kidney disease (use under medical supervision)
Not for: History of seizures (caution)

How it's used

In supplements

Typical doses: 5–10 g daily for gut or recovery goals, often split. Athlete protocols use 5 g post-exercise. Mix into water or a shake; timing matters less than consistency.

Regulatory status

Dietary supplement under DSHEA; glutamine is GRAS and is also a component of FDA-regulated medical foods.
GRAS (generally recognized as safe) for food use.

The gut-brain-immune triangle

Glutamine's gut reputation rests on real physiology: intestinal cells absorb it as a primary fuel, and the gut lining renews itself every few days. Under stress — intense training, illness, surgery — the gut can outspend the body's glutamine supply. That is why glutamine appears in gut-health protocols for athletes and post-infection recovery. The caveat: in normal daily life, the body makes enough, which is why general 'leaky gut' marketing runs ahead of the evidence.

Frequently asked questions

Does glutamine help with leaky gut?

It may help maintain the gut lining in specific high-stress contexts — post-exercise and post-illness trials show reduced permeability. In healthy people with normal digestion, evidence is limited, and the 'leaky gut' concept itself is still being defined clinically.

Should I take glutamine after workouts?

Optional. Post-exercise glutamine (5 g) is a reasonable, inexpensive addition for endurance athletes in heavy training blocks, mainly for immune support. It will not add muscle beyond what adequate protein provides.

Can glutamine upset the stomach?

Rarely — glutamine is one of the best-tolerated amino acids, and gut cells literally consume it. Very high single doses (15 g+) may cause mild bloating in some.

The bottom line

Glutamine is a genuine medical-nutrition heavyweight and a modest, well-tolerated tool for gut and immune support in stressed, heavily trained, or recovering bodies. For muscle growth, skip it and eat enough protein.

References

Glutamine in critical illness — literature search. PubMed (National Library of Medicine). https://pubmed.ncbi.nlm.nih.gov/?term=glutamine+critical+illness+randomized
Glutamine and intestinal permeability — literature search. PubMed (National Library of Medicine). https://pubmed.ncbi.nlm.nih.gov/?term=glutamine+intestinal+permeability+exercise
L-glutamine compound summary. PubChem (National Library of Medicine). https://pubchem.ncbi.nlm.nih.gov/compound/5961
Glutamine and exercise performance (review). PubMed (National Library of Medicine). https://pubmed.ncbi.nlm.nih.gov/?term=glutamine+exercise+performance+review