Oral L-glutamine for treatment-related oral mucositis

Evidence label: Mixed / regimen-specific · Clinical goal: prevent or reduce oral mucositis during chemotherapy or head-and-neck radiotherapy

Evidence at a glance

Population: people receiving fluorouracil-based chemotherapy or head-and-neck radiotherapy/chemoradiotherapy.
Intervention: oral L-glutamine powders or suspensions; doses, timing and comparators varied.
Result: several older placebo-controlled fluorouracil trials were negative, while some head-and-neck studies and a 2026 trial reported substantial benefit.

What was studied

Older randomized studies tested 16–18 g/day around fluorouracil treatment; a phase III placebo-controlled study concluded that its studied schedule did not alleviate mucositis.

A 2026 triple-blind trial randomized 84 head-and-neck radiotherapy patients to oral L-arginine, L-glutamine or maltodextrin three times daily from week 2 to treatment completion. The exact gram dose was not reported in the accessible abstract.

What the evidence shows

At week 5 of the 2026 trial, severe mucositis occurred in 92.9% of controls, 17.9% with arginine and 3.6% with glutamine (P<.001). The very large effect needs replication and scrutiny of adherence, grading and site practices.

Meta-analyses conflict. One 2021 analysis found less grade 3–4 mucositis (RR 0.53; 95% CI 0.32–0.88), while a head-and-neck analysis found no significant reduction in incidence (RR 0.98; 95% CI 0.94–1.02). MASCC/ISOO issued a setting-specific suggestion—not a universal recommendation—for oral glutamine during radiotherapy with concurrent chemotherapy.

Limits and uncertainty

Cancer type, treatment, dose, swish-versus-swallow instructions and endpoint definitions differ. The 2026 result should not be generalized beyond its exact protocol.

Reviews may include overlapping trials; they are used to judge consistency, not counted as independent clinical trials.

Safety and practical context

Glutamine can cause gastrointestinal symptoms and changes nitrogen handling. Severe kidney or liver disease may alter safety. Product purity and total nutrition plan matter.

Do not delay established oral care, pain control, hydration, nutrition support or photobiomodulation where protocol-supported. Fever, inability to swallow or suspected infection needs prompt assessment.

Questions for the care team

Is this the same dose and treatment setting as the supportive trial or guideline?
Should it be swallowed, used as a mouth rinse, or both—and for how long?
How will kidney/liver function, intake and mucositis severity be monitored?

Sources

Literature searched: October 15, 2026 · Record appraised: October 15, 2026

Educational evidence summary, not personal medical advice. Research regimens describe what was studied; they are not personal prescribing instructions and should not replace cancer treatment or individualized supportive care.