Bitterness in the mouth after eating may be caused by abnormal peristaltic function of the gastrointestinal tract. Bile is collected through the bile ducts and flows into the duodenum and small intestine to participate in fat digestion. If the peristaltic function of the gastrointestinal tract is restricted or abnormal, it makes bile flow backwards, which in turn causes patients to have bitter mouth symptoms. Patients are usually advised to take medication, such as mosapride, a drug that promotes intestinal motility, and 654-2, a drug that relieves spasm of the gastrointestinal tract, and Si Mo Tang, a traditional Chinese medicine that has the effect of easing the function of the gastrointestinal tract. In addition, patients can participate in exercise or carry out dietary therapy, such as taking a run or walk, to promote gastrointestinal peristalsis. The diet needs to be based on vegetables and fruits to facilitate digestion and thus eliminate symptoms.