L-Glutamine

Mechanism of Action

L-Glutamine is the most abundant amino acid in plasma and skeletal muscle. It is the primary fuel source for enterocytes (intestinal epithelial cells) and rapidly dividing immune cells (lymphocytes, neutrophils). Glutamine maintains intestinal tight junction integrity by modulating tight junction proteins (occludin, claudin-1, ZO-1), preventing intestinal hyperpermeability ('leaky gut'). It serves as a nitrogen shuttle between tissues, is a precursor for nucleotide synthesis (purines and pyrimidines), contributes to gluconeogenesis, and buffers ammonia via glutamine synthetase. During catabolic stress (illness, surgery, intense exercise), glutamine becomes conditionally essential.

Dosing Protocol

Notes

Cornerstone of any gut-healing protocol ('4R' gut restoration). The conditionally essential nature during stress means that athletes, surgical patients, and critically ill individuals have dramatically increased requirements. The glutamine paradox in cancer is unresolved — some tumors are glutamine addicted, but glutamine also supports immune function needed to fight cancer. Conservative approach: use for gut healing, discontinue in active cancer. Powder form is most practical at therapeutic doses (5-30g).

Stacking

• Probiotics
• Zinc Carnosine
• DGL Licorice
• Collagen
• Butyrate

Interactions

• Lactulose [MEDIUM] — Glutamine is converted to glutamate and then ammonia — may counteract lactulose in hepatic encephalopathy
• Anticonvulsants [LOW] — Glutamine converts to glutamate (excitatory) — theoretical concern in seizure-prone individuals
• Chemotherapy [MEDIUM] — Glutamine may protect normal tissue (beneficial) but theoretical concern of feeding tumors (glutamine-dependent cancers)

Contraindications

• Hepatic encephalopathy (glutamine to glutamate to ammonia conversion)
• Reye's syndrome
• Severe renal failure
• Some cancers are glutamine-dependent (discuss with oncologist)

Side Effects

• Generally well-tolerated
• Bloating at high doses
• Constipation
• Headache
• Theoretical excess glutamate conversion in sensitive individuals (excitotoxicity concern)

Key Papers

• 10.1186/1471-230X-12-57
• 10.1097/01.ccm.0000279192.84127.58
• 10.1016/j.nut.2017.03.003

Source Quality

Pharmaceutical-grade L-glutamine powder. Sustamine (dipeptide form: L-alanyl-L-glutamine) has superior stability and absorption. Brands: NOW L-Glutamine Powder, Thorne L-Glutamine, Jarrow L-Glutamine.

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