Glutamine

Glutamine

• Other names: Endari, Nutrestore, Enterex Glutapak-10, Resource Glutasolve, Sympt-X.

• Mechanism of action:

  • Glutamine is an amino acid normally produced in the body with various biochemical functions, including:

    • Protein, DNA precursor, and lipid synthesis

    • ATP energy production

    • Regulation of intestinal mucosa

  • Lungs, liver, brain, skeletal muscles, and adipose tissue have glutamine synthesis activity.

  • Glutamine is conditionally essential; endogenous synthesis may not meet demands during catabolic conditions (cancer, sepsis, infections, surgeries, traumas, intense exercise).

  • Skeletal muscles contain 50-60% of total free amino acids in the body, playing a key role in glutamine metabolism.

• Common indications/uses:

  • Exhaustive and prolonged exercise

  • Oral mucositis prevention secondary to chemotherapy

  • Short gut syndrome

  • Sickle cell disease

• Dosing:

  • Exhaustive prolonged exercise: 20-30 g tolerated without concerns; typically 10 g/day on current nutritional supplements.

  • Oral mucositis prevention secondary to chemo: 10-30 g daily [5].

  • Short bowel syndrome: 30 g daily with other nutritional supplements and growth hormone for up to 4 weeks [6].

  • Sickle cell disease: FDA-approved (Endari) dosing based on weight [7]:

    • Less than 30 kg: 5 g PO twice a day

    • 30-60 kg: 10 g PO twice a day

    • 65 kg or more: 15 g PO twice a day

• Evidence:

  • Exhaustive/prolonged exercise: A review of 55 studies showed glutamine supplementation increased muscle glycogen synthesis, reduced exercise-induced ammonia accumulation, and attenuated muscle damage markers (blood CK and LDH levels). However, there was limited effect on physical performance [8].

  • Oral mucositis prevention secondary to chemo: Recent guidelines suggest oral glutamine tablets in head and neck cancer patients receiving RT-CT, based on two RCTs showing glutamine (10-30 g daily during RT-CT) may prevent oral mucositis [5].

  • Short gut syndrome: A study showed oral glutamine (30 g daily), growth hormone (0.05 mg/kg/day), and enteral supplementation for 4 weeks improved intestinal absorptive capacity, plasma protein levels, and overall nutritional status in patients with short bowel syndrome [6].

  • Sickle cell disease: FDA approved Endari (L-glutamine supplement) in 2017 to reduce acute sickle cell flares in patients older than 5 years based on a phase 3 trial showing a significant decrease in pain crises and fewer hospitalizations [7].

• Safety concerns:

  • Minimal concerns at recommended doses (<44 g/day).

  • One case study reported hepatotoxicity with chronic glutamine supplementation in an athlete with increased alcohol consumption [9], warranting further research.

• Adverse reactions:

  • Commonly reported side effects include constipation, nausea, headaches, abdominal pain, cough, and muscle/joint pain.

• Drug interactions:

  • Lactulose: Glutamine may reduce the ammonia-lowering effects of lactulose when used for hepatic encephalopathy; should be monitored [10].