RAS is a chronic, inflammatory disease characterized by painful, ovoid ulcers and is observed worldwide but is rarely associated with systemic diseases.11
In this cross-sectional study, we explored the distribution of RAS, dietary factors, self-reported trigger factors and therapeutic methods among a study population from Nanjing and reported a prevalence of 21.4% in accordance with the literature. In Iran, the prevalence of RAS is 25.2% (10,291 respondents), in Brazil, 24.9% (2,427 respondents), and in Turkey, 22.8% (11,360 respondents).12–14
In this study, RAS was associated with fruits, vegetables, dairy products and drinking water intake through univariable analysis (p < .05). Other variables, including fried foods, fermented foods, spicy foods, eggs, gender and age, showed no statistically significant associations (p ≥ .05). Previous studies have shown that there is a significant association between vegetables, dairy products and RAS.8, 9, 15 However, in the present study, there was no significant association of these factors with RAS in the multivariable logistic regression, although a trend was found. This is likely due to the limited sample size. Further large-scale studies are necessary to verify our results. Dairy products might cause RAS due to milk, which has been reported as an allergic agent of RAS,9 causing adverse reactions in certain individuals. Vegetables might prevent RAS by increasing the serum levels of Zn and Se, which are reported to be low in RAS patients and are highly associated with immunity and oxidative stress.15
Another finding of our study was that multivariable logistic regression demonstrated a strong association between fruit intake and RAS. Although clinicians usually instruct patients affected with RAS to avoid acidic and spicy foods, it has been reported that local lemon salt (citric acid) is effective in treating chronic wound infections by significantly reducing infectious agents and boosting fibroblastic growth to hasten wound healing.16, 17 Furthermore, pomegranate has been reported to have immunomodulatory, strong antioxidant, and antibacterial characteristics, and pomegranate extract has been reported to offer protection against aspirin- and ethanol-induced gastric ulceration.18 As discussed above, sufficient fruit intake might prevent RAS through antimicrobial effects, immunoregulation and immunoregulatory effects.
Multivariable logistic regression also revealed that the consumption of drinking water might directly or indirectly affect the development of RAS. It is noteworthy that RAS was first found to be associated with drinking water in this study. Cardiovascular disease and RAS share common risk factors, such as hypertension and hyperlipidemia.15, 19 Insufficient water intake increases the plasma salt level and osmolality, which are known to be critical to health. Extracellular osmolality, affected by drinking water intake, is reported to promote the expression of the AQP5 gene, which facilitates the bidirectional movement of water across membranes depending on the osmotic gradient and hydrostatic pressure. As discussed above, reduced water intake, a common phenomenon resulting from various factors, including decreased kidney function, social isolation, and cognitive disorders,20 might promote the increase of plasma osmolality and lead to RAS.
Our study assessed the types of treatments used by patients with RAS to assess the level of patient awareness of the disease. Less than half (72, 44.7%) of the RAS group had ever received treatment for RAS, which was lower than that reported in another study,7 and approximately one-third of those who were treating their RAS lesions were using ATs instead of conventional medicine, indicating a high prevalence of AT use, despite a lack of randomized controlled trials proving the benefit of ATs in treating RAS. These results indicated that patient education on the importance of RAS treatment is needed.
We acknowledge a bias towards a younger population that might result from a high percentage of students in the chosen neighbourhood communities. However, considering that no significant association was found between age and RAS in this study, this bias should not affect the generalizability of our results. Nevertheless, despite our attempts to choose districts representative of different demographic statuses, including participants solely from Nanjing poses some inevitable limitations on the generalizability and extrapolation of the results to other urban and rural areas.