Heartburn, also known as gastric reflux or indigestion, happens after you eat and food is in your stomach. In the stomach, food is broken down by acids. Usually these acids stay in your stomach because a valve blocks the acids from going up the esophagus. Sometimes this valve doesn't work properly because the muscle weakens. When this happens, gastric acids can travel up the esophagus and cause a burning sensation -- this is heartburn. When these acids travel up into the mouth and then down...