Acid reflux is a common irritation of the walls of the esophagus after eating. As many as 36% of all healthy Americans experience this condition. Commonly called "heartburn", acid reflux occurs when the Lowe espohageal sphincter or LES fails to remain closed; a properly functioning sphincter, on the other hand, holds food and acid away from the esophagus during the digestion process.

For acid reflux to occur, the LES relaxes, thereby allowing the food and acid to seep into the esophagus. The acid seepage in turn causes irritation or burning. Secondary peristalsis, or the movement of the esophagus caused by swallowing pushes about 90% of the food and acid back into the stomach. The LES closes again for normal digestion. The remaining 10% of food and acid left in the esophagus is neutralized by saliva.

While many people experiences with acid reflux is asymptomatic, acid reflux can be part of a larger problem. Acid reflux is lumped into a much larger category called Gastroesophageal Reflux Disease or GERD. According to GERD.com, this is "Any symptomatic clinical condition or change in tissue structure that results from the reflux of stomach or duodenal contents into the esophagus."

GERD is said to be caused by many different factors. For example, transient LES relaxation, decreased LES resting tone, impaired esophageal clearance, delayed gastric emptying, decreased salivation, and impaired tissue resistance.

An individual's lifestyle can also be a factor in causing this condition. Smoking, large meals, fatty foods, caffeine, pregnancy, obesity, body position, drugs, and hormones may all exacerbate GERD. Also, hiatal hernia frequently accompanies severe GERD. Furthermore, wearing tight clothing, lying down after a meal, or bending over can help trigger acid reflux.

It is recommended that people who have acid reflux keep a diary of when symptoms occur. This way, the individual can slowly become aware of any patterns caused by certain activities and consumption of certian foods; this will help them steer clear of the behaviors causing the problem.