Disclosure: We may earn a commission if you buy through links on this page — at no extra cost to you. Learn more.
Statements on this site have not been evaluated by the Food and Drug Administration.
Products and information are not intended to diagnose, treat, cure, or prevent any disease. Learn More
Products and information are not intended to diagnose, treat, cure, or prevent any disease. Learn More
Summary
L‑glutamine is a conditionally essential amino acid important for enterocyte fuel, immune function, and nitrogen transport. In adults, supplementation is primarily used for gut support and recovery from stressors; cognitive benefits are indirect and context‑dependent.
Our Picks
L-Glutamine — Thorne
An amino acid that promotes post-exercise muscle cell repair and supports gastrointestinal and immune system health. NSF Certified for Sport®.
Mental Clarity, Focus, and Energy
- Indirect effects only: Any changes in mental clarity or energy are likely secondary to improved GI comfort, sleep, or recovery from physiological stress rather than direct CNS effects at typical doses.
Brain Health
- Mechanisms: By supporting gut integrity and immune balance, glutamine may reduce systemic inflammatory load that can influence brain function. Direct human cognition trials are limited outside clinical settings.
Gut Health
- Evidence supports roles in maintaining intestinal barrier function and reducing GI symptoms in stress‑related or intensive training contexts.
- Common protocols use 5–10 g/day, often split doses; higher intakes have been used short‑term in clinical settings under supervision.
- Tolerability is generally good; GI bloating can occur at higher single doses.
Brain-Gut Axis
- By fueling enterocytes and supporting mucosal integrity, glutamine may lessen pro‑inflammatory signaling from the gut, indirectly benefiting mood and stress resilience.
Evidence Summary
Benefit Area | Evidence Quality | Effect Noted | Notes |
Mental Clarity | Limited | Indirect via gut comfort | No direct cognition trials |
Focus Enhancement | Limited | Indirect via reduced GI distress | Secondary benefit |
Energy Support | Limited | Recovery support | Context‑dependent |
Brain Health | Limited–Emerging | Reduced inflammatory signaling (indirect) | GI‑first evidence base |
Gut Health | Moderate | Barrier support and symptom reduction | 5–10 g/day common |
Brain–Gut Optimization | Emerging | Improved mucosal integrity | Indirect evidence |
Typical Dosing Instructions
- Standard dose: 5–10 g/day, split into 2–3 doses
- Timing: With food or between meals based on tolerance; avoid large single boluses if bloating occurs
- Form: Powder mixed in water or capsules
- Notes: Trial 2–4+ weeks for GI endpoints; pair with diet and stress‑management for best results
Safety Considerations
- General safety: Generally well tolerated at typical supplemental doses in healthy adults
- Common effects: Bloating or mild GI discomfort at large single doses
- Contraindications and cautions: Use caution in severe liver disease or significant renal impairment; separate from medications if absorption interactions are a concern
- Populations: Limited data in pregnancy or pediatrics; avoid unless clinician‑directed
- Monitoring: Track GI symptoms, stool pattern, and overall recovery; reduce dose if persistent bloating occurs
References
- A Randomized Placebo‑Controlled Trial of Dietary Glutamine Supplements for Post‑Infectious Irritable Bowel Syndrome, Gut, 2018-08-14
- A systematic review and meta‑analysis of clinical trials on the effects of glutamine supplementation on gut permeability in adults, Amino Acids, 2024-10-13
- Glutamine supplementation reduces markers of intestinal permeability during running in the heat in a dose‑dependent manner, European Journal of Applied Physiology, 2017-10-20
- The effects of acute oral glutamine supplementation on exercise‑induced gastrointestinal permeability and heat shock protein expression, Cell Stress & Chaperones, 2014-07-26
- A systematic review: Role of dietary supplements on markers of exercise‑associated gut damage and permeability, PLoS One, 2022-04-13
- Glutamine and the regulation of intestinal permeability: from bench to bedside, Current Opinion in Clinical Nutrition & Metabolic Care, 2017-01-01
- Glutamine and intestinal barrier function, Amino Acids, 2015-06-26
- Glutamine Supplementation Enhances the Effects of a Low FODMAP Diet in Irritable Bowel Syndrome Management, Frontiers in Nutrition, 2021-12-16