Reply:

At the time of publication, very few population-based studies had investigated the roles of diet and lifestyle habits in irritable bowel syndrome (IBS) in developing countries, particularly in China.¹ The aim of this preliminary study was to investigate the association between diet and lifestyle habits and IBS. Thus, we investigated information prior to the first occurrence of the syndrome, excluding the other direction, such that IBS may have been the cause of specific diet and lifestyle habits. Our workplace was a large-scale general hospital in southern China. The patients admitted to the hospital were from all regions of the country. Thus, the patients enrolled in our study originated from different parts of the country with different socioeconomic statuses or different types of environmental pollution. Furthermore, in the design of this study, the first principle was to set strict criteria for the enrollment of patients who both fulfilled the diagnosis of IBS and also had a relatively clear memory regarding changes in clinical symptoms. These criteria were clearly described in our paper. Although this approach significantly excluded a substantial number of patients who may have been IBS patients, it also improved the overall quality of our study. Furthermore, there had also been an IBS study with few but high quality samples.² We did not discuss the limitations of the conclusion drawn from the present study; however, it is generally accepted that the level of evidence regarding case control studies is relatively low according to the grading system of evidence-based medicine.³ Thus, it is more appropriate to regard our research as a reference for further research, such as cohort studies or randomized clinical trials, rather than an unalterable conclusion.