💊 What it does
L-glutamine is the most abundant amino acid in the body and the primary fuel source for intestinal cells (enterocytes) and immune cells. During intense exercise, illness, surgery, or severe stress, glutamine is consumed faster than the body can synthesise it, making it conditionally essential. In sports nutrition, evidence supports glutamine for reducing exercise-induced gut permeability (leaky gut), supporting immune function during heavy training, and aiding recovery. In clinical nutrition, IV glutamine is used for critically ill patients and those recovering from gut surgery.
👤 Who needs it
Endurance athletes and those doing very high-volume training who experience digestive issues or frequent illness. People recovering from gut surgery, serious illness, or significant stress. Those with inflammatory bowel disease (IBS, Crohn's, ulcerative colitis) — emerging evidence for gut lining support. People taking NSAIDs regularly (which damage gut lining).
🥦 Food sources first
Glutamine is the most abundant amino acid in protein-rich foods: tofu, tempeh, edamame, lentils, chickpeas, cabbage, spinach, parsley. A protein-rich diet provides plentiful glutamine. Supplementation provides doses far above what is achievable from food in acute situations.
🗓 When to supplement
For athletes doing very high-volume training (above 10 hours/week) who experience gut issues or recurrent illness. For gut health support in people with confirmed intestinal permeability. Not necessary for recreational exercisers with adequate protein intake.
🏷 Best form to look for
Pure L-glutamine powder is cost-effective and tasteless in water. Pharmaceutical-grade L-glutamine is used in clinical settings. Avoid blended products where glutamine dose is unclear.
⏰ When to take it
On an empty stomach for gut health applications (reaches intestinal cells directly). Post-workout for recovery. Can also be taken at night to support overnight repair.