Gastroesophageal reflux disease (GERD), lower esophageal sphincter (LES), stomach acid, esophagus, heartburn, chest pain, sour taste, Barrett’s esophagus, cancer, regurgitation of food/liquid, difficulty swallowing, sore throat, hoarseness, coughing/wheezing/nausea after eating/bad breath/chest pain not related to eating or exercise/unexplained weight loss/vomiting/difficulty sleeping due to nighttime heartburn/asthma-like symptoms such as shortness of breath/chronic sore throat/laryngitis/dry mouth bad taste in your mouth and tooth erosion.,