Gastroesophageal reflux disease (GERD) is a condition where acid contents in your stomach consistently leak back up into your esophagus. Acid reflux happens because the lower esophageal sphincter (LES) doesn’t tighten or close properly. This allows digestive juices and other contents from your stomach to rise into your esophagus. Having acid reflux or heartburn every now and then is normal, but if you have it more than twice a week over several weeks, you may suffer from GERD. Anyone can develop GERD at any time, but your risk increases after 40 years of age, and if you are obese, pregnant, or smoke.