Introduction
Gastrointestinal symptoms, primarily abdominal pain, regurgitation, dyspepsia, diarrhea, and constipation,1,2 are common, with a prevalence of 61% (45,498/71,812) in the US general population.3 They negatively influence the quality of life and productivity and indicate the probability of functional or organic gastrointestinal diseases.4,5 It has been shown that gastrointestinal symptoms are closely associated with psychological problems, such as anxiety and depression.6–8 This association can be explained by the action of the brain-gut axis that an individual’s feelings can influence his or her gastrointestinal function, and vice versa. In addition, the gut microbiota, called the human second brain, plays a critical role in the regulation of the central nervous system.9,10 Thus, the correction of…