L-Glutamine
The primary fuel for the cells lining your gut. Heals leaky gut, supports immune function, and aids recovery from intense training.
Strong evidence in clinical settings: critically ill patients, post-burn recovery, IBD, short bowel syndrome. Moderate evidence for leaky gut markers (intestinal permeability) and IBS-D symptoms. Weak evidence for general muscle building. Effects: 2–4 weeks for gut symptoms.
L-Glutamine is the most abundant free amino acid in the bloodstream and the primary energy source for enterocytes (the cells lining your intestines) and lymphocytes (immune cells). It's technically non-essential (the body makes some), but becomes conditionally essential under stress — illness, injury, intense exercise, gut inflammation. Most clinically useful for gut barrier repair (leaky gut, IBD, post-antibiotic recovery), immune support during heavy training, and post-surgery healing. Less convincing for general muscle building, despite the bodybuilding-supplement reputation.
- Form
- L-Glutamine powder — slightly sweet, dissolves in water. Capsules also fine but less practical for higher doses.
- Dose
- 5 g/day for general gut support. 10–20 g/day for active leaky gut, IBD, or post-antibiotic recovery (split across the day). 5–10 g post-workout for athletes in heavy training.
- Timing
- Empty stomach for gut effects (between meals, or first thing AM). With water or in a smoothie. Post-workout for recovery use.
- Schedule
- Daily during a gut-repair protocol (typically 4–12 weeks). Ongoing for athletes in heavy training.
- Side effects
- Generally very well-tolerated. Mild GI upset uncommon. Some report increased thirst.
- Interactions
- Lactulose (used in hepatic encephalopathy — glutamine can worsen). Anti-seizure medications (theoretical glutamate-related interaction).
- Contraindications
- Cirrhosis with hepatic encephalopathy — glutamine converts to ammonia, can worsen encephalopathy. Reye's syndrome history. Some seizure disorders (excitatory amino acid concern).
- Lab markers
- Not routinely tested. Functional markers: intestinal permeability (lactulose-mannitol ratio), zonulin, calprotectin if monitoring gut inflammation.
- Food sources
- Beef, eggs, fish, dairy (cottage cheese, yogurt), beans, cabbage, spinach, parsley. Whey protein is glutamine-rich. Most omnivores get plenty from food; supplementation targets clinical doses.
Pairs with
Probiotics + zinc carnosine + slippery elm (gut-healing stack). Collagen peptides (additional gut lining support — proline content). NAC + glycine (glutathione precursor stack — protects gut cells).
within Amino acids & derivatives