In a related study, the investigators have found evidence that patients with Barrett's esophagus have a leak for oral sucrose to leave their upper gastrointestinal tract, enter the blood, and be filtered into urine. The amount of sucrose appearing in an overnight urine sample can be used to indicate the presence of Barrett's esophagus and/or esophagitis in a patient reporting with reflux (GERD) symptoms. The leak is presumably in the Barrett's epithelium itself. This phenomenon will be used to test if a standard 8 week therapy of Nexium in a first-time-presenting GERD patient can reduce the leak as a means of assessing the efficacy of the drug in that patient. The investigators predict that Nexium will reduce leak in esophagitis but not Barrett's patients.