L-Glutamine
Also known as Glutamine
L-Glutamine is the most abundant amino acid in the body and the primary fuel source for intestinal cells and immune cells. Under stress, surgery, illness, or intense exercise, demand outpaces supply. Supplementation has the strongest clinical evidence for restoring gut barrier integrity, reducing intestinal permeability ('leaky gut'), and supporting immune function during periods of high physiological stress.
Benefits
Supports gut barrier integrity
ModerateGlutamine is the primary fuel for enterocytes (gut lining cells). Supplementation reduces intestinal permeability and supports recovery of the gut lining after illness, stress, or intense exercise.
Immune support during stress
ModerateLymphocytes and macrophages rely heavily on glutamine. Clinical trials in surgical and critically ill patients show improved immune markers with supplementation.
Reduces exercise-induced gut permeability
ModerateEndurance athletes commonly experience increased gut permeability during prolonged exertion; glutamine attenuates this effect.
Pros & cons
Pros
- Strong mechanistic rationale for gut health
- Very safe at typical doses
- Inexpensive in powder form
Cons
- Evidence weaker for muscle preservation in healthy athletes than once believed
- Powder has a slightly sweet flavour that some find unpleasant in high doses
Side effects
GI discomfort at high doses
Large doses can cause bloating or cramping in some people.
How to take it
Typical dose
5–15 g per day
Timing
With meals or post-workout for gut support; spread across the day
Common forms
Tip: 5 g/day is sufficient for general gut support. Clinical gut-permeability protocols often use 15–30 g/day split across meals.
What the research says
Glutamine and gut permeability
ModerateSupplementation reduces markers of intestinal permeability in critically ill patients, surgical patients, and endurance athletes.
Glutamine and immune function
ModeratePerioperative glutamine supplementation reduces infection rates and hospital stay duration in multiple clinical trials.
How it connects
Relationships between L-Glutamine and other supplements in the matrix.
Glutamine restores the gut lining while probiotics help balance the microbiome — a complementary gut-health stack.
Compare the pairingBoth are conditionally essential under stress and support gut and immune function through complementary pathways.
Compare the pairingCommon in post-workout recovery stacks; glutamine for gut integrity and creatine for muscle energy replenishment.
Compare the pairingImportant cautions
- Caution in individuals with liver disease or seizure disorders — glutamine can influence ammonia and glutamate metabolism.
- Not for use in patients with active cancer without oncologist approval.
More Amino Acids
Creatine
The most-studied performance and cognition supplement.
Glycine
A calming amino acid for sleep, collagen, and metabolic health.
L-Arginine
The nitric oxide precursor for blood flow and cardiovascular health.