L-Glutamine and Antibiotic Absorption in SIBO
L-glutamine supplementation does not inhibit the absorption of metronidazole or rifaximin, and furthermore, glutamine supplementation is not recommended for SIBO treatment as it provides no benefit for intestinal rehabilitation or symptom improvement. 1
Evidence Against Glutamine Supplementation in SIBO
The ESPEN guidelines explicitly recommend against adding glutamine to the diet for promoting intestinal rehabilitation in patients with chronic intestinal failure and bacterial overgrowth. 1
An 8-week randomized, placebo-controlled, crossover study in patients with short bowel syndrome found no effects of glutamine supplementation on bowel morphology, transit, D-xylose absorption, or stool losses. 1
There is no evidence that glutamine interferes with antibiotic pharmacokinetics or absorption in the gastrointestinal tract. 1
No Drug-Nutrient Interaction Concerns
Rifaximin is a non-absorbed antibiotic that acts locally in the gastrointestinal lumen and is the preferred first-line treatment for SIBO at 550 mg twice daily for 1-2 weeks, achieving 60-80% eradication rates. 2, 3
Metronidazole, while systemically absorbed, has no documented interactions with amino acid supplements like glutamine. 1
The primary concern with metronidazole in SIBO treatment is its lower efficacy compared to rifaximin and the risk of peripheral neuropathy with long-term use—patients should stop immediately if numbness or tingling develops in the feet. 2
Clinical Recommendation
Focus antibiotic therapy on rifaximin as first-line treatment rather than metronidazole, which is less effective for SIBO. 2
If glutamine supplementation is being considered for "leaky gut," discontinue it as it provides no proven benefit for intestinal rehabilitation in this context. 1
Direct nutritional support toward monitoring and correcting actual micronutrient deficiencies common in SIBO: iron, vitamin B12, and fat-soluble vitamins (A, D, E, K). 1, 3
Consider bile salt sequestrants (cholestyramine or colesevelam) if bile salt malabsorption occurs, particularly with terminal ileum involvement or dilated bowel loops. 1, 2