It is not uncommon to have heartburn, especially after eating spicy food or a large meal. According to the Cleveland Clinic, about 1 in 10 adults experience heartburn at least once a week. However, if you have heartburn more than twice a week, you may have a more serious condition called gastroesophageal reflux disease (GERD). GERD is a digestive disorder that causes stomach acid to back up into the throat. Frequent heartburn is the most common symptom of GERD, which is why the burning sensation is often accompanied by a sour or bitter taste in the throat and mouth.