Almost all of us have experienced heartburn at one time or another. Heartburn is the most common symptom of gastro-esophageal reflux (GERD), also known as acid reflux. Acid reflux occurs when a sphincter called the lower esophageal sphincter (LES) at the lower end of the esophagus does not work properly, causing stomach acid to back up in the esophagus. Heartburn, a painful burning sensation in the chest or throat, is the result.
