Acid reflux or GERD (gastroesophageal reflux disease) occurs when the liquid that is in the stomach backs up into the esophagus. This is usually a condition which persists throughout the life of the individual. Because the acid backs up into the esophagus, the esophagus may be damaged. Acid reflux (GERD) can have many causes. The action of the lower esophageal sphincter (LES) may be one cause. The esophagus connects to the stomach. There is a muscle ring that goes around the end of the esophagus at the point where it meets the stomach. This is the LES. When we eat or drink the LES allows the food to pass into the stomach and then the muscle ring closes so the food does not reflux. People with acid reflux (GERD) may have abnormalities with their LES. The LES may have a weak contraction so there is a very good chance of reflux. Or, the LES may be too relaxed. The longer the LES is open (relaxed) reflux can easily occur. Another cause of acid reflux (GERD) is a hiatal hernia. Some people with acid reflux have hiatal hernias and some do not. Hiatal hernias are not a pre-requisite for acid reflux, but a large amount of people with acid reflux DO have hiatal hernias. A hiatal hernia disrupts the location of the LES. The LES should be on a level with the diaphragm but due to the hiatal hernia the LES is pushed up and lies in the chest. This is a problem because the diaphragm is a large part of helping the LES to prevent reflux. Now the pressure of both the LES and diaphragm are not working as a strong unit. The hiatal hernia contributes to the reflux because of the decreased pressure. Acid reflux can also be caused by a hiatal hernia due to the hernial sac. The location of the sac is near the esophagus. Acid gets trapped in the sac. Because the sac is so close to the esophagus, when the LES relaxes, it is easy to reflux. The hiatal hernia can lead to acid reflux in a third way. Normally the esophagus connects to the stomach at an angle creating a flap of tissue. The hiatal hernia leads to the flap becoming warped and therefore it is useless to stop reflux. People with acid reflux have a problem with the contraction of the esophageal muscles when they swallow. This is an issue because the contraction pushes all of the items in the esophagus into the stomach. If there is not a good contraction then the acid does not get pushed back and remains in the esophagus. Smoking disturbs the clearing of the esophagus too. It takes about six hours from the last cigarette you smoke for the effect on the esophagus to wear off. Acid reflux is most common after meals. It is always better to be vertical so gravity can help the acid move down into the stomach. Large meals are not recommended for people with acid reflux. There are many different reasons people may have acid reflux. Learning the cause may help in your quest to relieve some of the discomfort of acid reflux.