Gastroesophageal reflux disease, or GERD, occurs when acid from the stomach backs up into the esophagus. Normally, food travels from the mouth, down through the esophagus and into the stomach. A ring of muscle at the bottom of the esophagus, the lower esophageal sphincter (LES), contracts to keep the acidic contents of the stomach from “refluxing” or coming back up into the esophagus. In those who have GERD, the LES does not close properly, allowing acid to move up the esophagus.