Glutamine is the body's most common amino acid and serves both as fuel and as a signaling molecule for the gut, immune system, and other tissues.
What is glutamine?
Glutamine is a non‑essential amino acid, but becomes “conditionally essential” during stress, infection, trauma, and intense training because utilization then rises sharply. Intestinal cells (enterocytes) and immune cells use glutamine as their primary fuel, more than glucose in many situations.
Fuel for the gut barrier
Glutamine is the main fuel for the cells of the intestinal mucosa and is needed to maintain the so‑called tight junctions between cells. Clinical studies show that glutamine supplementation can reduce increased intestinal permeability, also called “leaky gut,” after surgery, hard training, and certain intestinal diseases.
Affects the gut flora (microbiome)
Studies in humans and animals show that glutamine supplementation can change the composition of the gut flora, including by affecting the Firmicutes/Bacteroidetes ratio and increasing certain bacterial genera linked to better metabolic health. These changes are associated with reduced bacterial overgrowth and an improved metabolic profile, but findings are still preliminary in healthy individuals.
Support for the immune system
Immune cells such as lymphocytes and macrophages use glutamine intensively during activation and proliferation, making glutamine central to immune function. In stressed states (e.g., trauma, intensive care, hard endurance training), glutamine supplementation has improved markers of immune function in several studies, such as secretory IgA and T‑cell responses, and reduced infection rates.
Targeted benefits in IBS and increased permeability
In a randomized, placebo‑controlled study in people with IBS‑D (diarrhea‑predominant IBS) after infection, 8 weeks of glutamine supplementation produced a clear reduction in symptoms and normalization of intestinal permeability compared with placebo.
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