BackgroundThis study aimed to evaluate the effect of oral glutamine suspension on salivary levels of transforming growth factor beta 1 (TGF-β1), a cytokine involved in inflammation and Tumor progression, and the severity of radiation-induced oral mucositis (RIOM) in head and neck cancer patients. This is the first study to investigate the impact of glutamine on TGF-β1 levels in head and neck cancer patients with radiation induced oral mucositis (RIOM). MethodsIn this randomized controlled clinical trial, 50 HNC patients were enrolled and received either glutamine oral suspension or maltodextrin as a placebo from the baseline of RIOM to the end of radiotherapy. Salivary TGF-β1 levels were measured at baseline and after treatment. Also, RIOM was assessed using the World Health Organization (WHO) Oral Toxicity Scale, the Oral Mucositis Assessment Scale (OMAS), the Pain Visual Analog Scale (Pain-VAS), the incidence of opioid use, and body mass index (BMI). ResultsGlutamine significantly reduced salivary TGF-β1 levels and improved RIOM symptoms, such as pain, opioid use, and weight loss. The reduction of TGF-β1 levels was associated with the improvement of RIOM severity. ConclusionGlutamine may modulate the inflammatory response and enhance wound healing in RIOM by decreasing salivary TGF-β1 levels. These findings support the use of glutamine as a potential intervention for RIOM and nutritional support for improving radiation sensitivity. Trial RegistrationThis study was registered on clinicalTrials.gov with identifier no. NCT05856188.