Therapeutic Diet for Xerostomia in Head and Neck Cancer Patients: A Narrative Review Xerostomia significantly disrupts nutritional status, increases oral complications, and reduces quality of life in head and neck cancer (HNC) patients. This systematic review aimed to determine the best dietary interventions for the management of xerostomia in HNC patients by examining available therapies and their effects. A search of PubMed, Web of Science, and Scopus was conducted for randomised controlled trials, interventional, and observational studies published between December 2000 and December 2021. English articles involving adult HNC patients undergoing or having completed anti-cancer therapy were included. Non-HNC xerostomia causes and abstracts were excluded. Risk of bias was assessed using the Cochrane and Joanna Briggs Institute (JBI) tools. Fifteen studies were included out of 533 articles. Acidic candy, ginger extract, chewing gum, vitamin C/E supplements, and thyme honey were identified as helpful in reducing xerostomia. Dietary counselling and awareness of diet modifications improved symptoms, nutrition, and quality of life. Acidic candy was particularly effective in stimulating salivary flow but may cause dental enamel erosion, and timing precautions were necessary for thyroid patients’ post-radioactive ablation. Hydration techniques were commonly adopted by patients for symptom alleviation. Dietary modifications show promise in managing xerostomia in HNC patients, although further large-scale, randomised trials are needed to confirm these findings and explore new interventions.