Updated February 23, 2015.
You have just enjoyed a big dinner at your favorite Mexican restaurant, hot and spicy, just the way you like it. But now you're paying for it with that uncomfortable burning sensation in your chest and throat. Heartburn, which has nothing to do with the heart but can mimic a heart attack, is not life-threatening. In fact, occasional heartburn is fairly common. However, frequent heartburn may be a sign of a more serious problem called gastroesophageal reflux disease (GERD), a chronic condition caused by irritating stomach acids that back up into the esophagus, the tube that links your mouth to your stomach.

Heartburn and the Digestive System

So how and why does heartburn happen?

To fully understand heartburn, it is important to understand the mechanisms of a healthy digestive system. Your digestive tract starts with your mouth, where food is chewed and mixed with saliva, starting the process of digestion. From here, food travels to the esophagus, or swallowing tube. This muscular tube makes tiny contractions, called peristalsis, to move the food to the stomach.

The esophagus and stomach are connected by a band of muscle fibers called the lower esophageal sphincter (LES). Normally, the LES works like a valve, opening to allow food to pass into the stomach and closing to keep food and digestive juices from flowing back into the esophagus. But if the sphincter relaxes when it shouldn't, or becomes weak, stomach acid can flow backward into the esophagus causing the burning sensation we know as heartburn.

Heartburn Triggers

Some people have a naturally weak LES that is unable to withstand normal pressure from the contents of the stomach. But other factors also can contribute to this weakening, such as:

• Eating foods that often trigger heartburn, such as acidic foods (e.g. tomatoes and citrus fruits)
• Drinking alcohol
• Smoking cigarettes
• Having certain medical conditions, such as diabetes and asthma

Excessive pressure on the abdomen can put pressure on the lower esophageal sphincter, allowing stomach acid to enter the esophagus, or even the mouth. Pregnant women and overweight people are especially prone to heartburn for this reason. Even wearing tight-fitting clothes can cause pressure in the area. And because the esophageal sphincter is located in the upper part of the stomach, heartburn sufferers can experience increased symptoms when they lie down or have a full stomach.

Other Factors

There are other factors that also may contribute to reflux. Some people have abnormal muscle or nerve function in the stomach that affects motility, the ability of the stomach muscles to contract in a normal fashion. This results in food spending more time in the stomach, increasing the chance of acid seeping back into the esophagus.

Other medical conditions that may contribute to GERD include asthma, diabetes and a hiatal hernia. Hiatal hernia is a condition in which there is an opening in the diaphragm, the muscular wall below the lungs that separates the chest cavity from the abdominal cavity – permitting the upper stomach to protrude through the hole into the chest, impairing the LES's ability to prevent reflux.

Often, more than one of these factors contributes to the development of GERD, only underscoring the importance of consulting with your physician for the appropriate diagnosis and course of treatment. Understanding the body's digestive system can help heartburn sufferers understand their symptoms, make helpful lifestyle modifications and communicate with their doctors.

<sub>Sources:

"Heartburn and GERD FAQ." American College of Gastroenterology. 8 Jan 2010

"Heartburn, Gastroesophageal Reflux (GER), and Gastroesophageal Reflux Disease (GERD)." NIH Publication No. 07–0882 May 2007. National Digestive Diseases Information Clearinghouse (NDDIC). 8 Jan 2010

"Is it just a little HEARTBURN or something more serious?." American College of Gastroenterology. 8 Jan 2010</sub>