Background: Recurrent aphthous stomatitis (RAS), a common oral mucosal disorder characterized by chronic, inflammatory, and ovoid ulcers, has a complex aetiology. The purpose of the study was to investigate the specific dietary factors influencing the prevalence of RAS.Methods: A total of 754 participants aged 18 to 59 years in Nanjing were enrolled in this descriptive cross-sectional study. An anonymous questionnaire was adopted to investigate the distribution of RAS, dietary factors, self-reported trigger factors, and therapeutic methods.Results: Among all participants, the prevalence rate of RAS was 21.4%. The univariable analysis suggested fruits, dairy products, vegetables, and drinking water, but not fried foods, fermented foods, spicy foods, and eggs, as preventive factors of RAS. After adjusting for age and sex, multivariable regression analysis suggested fruits (adjusted odds ratio [aOR] = .430, 95% confidence interval [CI] = [.218-.847], p = .015) and drinking water (aOR = .294, 95% CI = [.119-.726], p = .008) as protective factors of RAS. Conclusion: This study suggests that consumption of fruit and drinking water is negatively associated with RAS and dietary factors play an important role in RAS development. These results imply a potential adjunctive and complementary role of food in RAS treatment and some potential, simple, and feasible means for RAS prevention.