Is consuming L-glutamine (L-glutamine) beneficial?

L-Glutamine Supplementation: Evidence-Based Recommendations

L-glutamine supplementation is not recommended for general consumption as there is insufficient consistent clinical data to support its routine use for healthy individuals, though it may be beneficial in specific medical conditions like acute pancreatitis when parenteral nutrition is required.

Evidence for L-Glutamine in Clinical Settings

Acute and Critical Illness

• When enteral nutrition is not feasible in acute pancreatitis and parenteral nutrition is indicated, parenteral glutamine should be supplemented at 0.20 g/kg per day of L-glutamine 1
• Several meta-analyses have shown beneficial effects of glutamine supplementation in patients with acute pancreatitis, including:
  • Decreased infectious complications
  • Reduced mortality
  • Shortened hospital stays
  • Improved serum albumin concentrations
  • Decreased C-reactive protein levels 1

Surgical Patients

• In surgical patients receiving parenteral nutrition, glutamine supplementation has shown some benefits in reducing hospital length of stay and complications, though evidence quality varies 1
• A standard dosage of glutamine (0.5 g/kg/day) appears safe in surgical patients, but strong recommendations for routine use are not justified 1

Cancer Patients

• Current guidelines do not recommend glutamine supplementation during conventional cytotoxic or targeted cancer therapy 1
• There is insufficient consistent clinical data to recommend glutamine to prevent radiation-induced side effects such as enteritis, diarrhea, stomatitis, esophagitis, or skin toxicity 1

Kidney Disease

• In critically ill patients with acute kidney injury or chronic kidney disease with kidney failure, high-dose parenteral glutamine should not be administered 1
• The REDOX study showed that high doses of glutamine administered intravenously or enterally may be harmful in critically ill patients with kidney failure 1

Dosing Considerations

• When indicated in specific clinical scenarios (such as acute pancreatitis requiring parenteral nutrition), the recommended dose is 0.20 g/kg per day of L-glutamine 1
• For parenteral nutrition in pancreatic disease, a dose of >0.20 g/kg per day of L-glutamine (>0.30 g/kg per day Ala–Gln dipeptide) should be considered 1
• In healthy individuals, acute intakes of approximately 20-30g appear to be without ill effects, though benefits remain unproven 2

Potential Benefits and Mechanisms

• Glutamine is the most abundant amino acid in the body and serves multiple functions:
  • Nitrogen shuttle
  • Contributor to production of other amino acids, glucose, and glutathione
  • Principal metabolic fuel for intestinal enterocytes, lymphocytes, and macrophages 3
  • Essential nutrient for immune cell function 4

Limitations and Cautions

• Despite theoretical benefits, well-controlled studies in healthy, well-nourished humans have not supported the suggested reasons for taking glutamine supplements (immune system support, increased glycogen synthesis, anticatabolic effect) 2
• In states of critical illness or injury, plasma glutamine levels can decrease significantly, which has been correlated with increased mortality in some studies 5
• Glutamine becomes "conditionally essential" during certain states of illness or injury 5

Clinical Decision Algorithm

1. For healthy individuals: Routine supplementation not recommended due to insufficient evidence of benefit
2. For patients with acute pancreatitis requiring parenteral nutrition: Consider supplementation at 0.20 g/kg/day
3. For surgical patients receiving parenteral nutrition: May be safe but benefits are not consistently demonstrated
4. For cancer patients: Not recommended during conventional therapy
5. For patients with kidney failure: High-dose parenteral glutamine should be avoided

The evidence suggests that L-glutamine supplementation should be reserved for specific clinical scenarios rather than general consumption, with careful consideration of the patient's condition, nutritional status, and overall treatment plan.