Heartburn is pain, discomfort or a burning sensation felt at the bottom of one's throat or in one's upper chest − usually just behind the breastbone. Though many people talk about acid reflux and heartburn synonymously, acid reflux is actually the cause, and heartburn is one symptom. Heartburn affects more than 60 million Americans at least once a month, and some research shows that more than 15 million of us experience it daily. 

Though occasional heartburn isn't cause for alarm, it can be debilitating and worrisome when it occurs regularly. When acid reflux progresses to a more serious condition known as GERD, it could damage one's esophagus and even lead to cancer. Understanding what causes heartburn may be helpful in avoiding the discomfort and inconvenience of experiencing it too often.

What causes heartburn?

Heartburn can be experienced for many reasons, but it's usually caused by acid reflux. Acid reflux is what happens when acid from your stomach repeatedly rises into your esophagus. Dr. Jamie Bering, a gastroenterologist at Mayo Clinic in Arizona, explains that at the bottom of the esophagus is a band of muscle, called the lower esophageal sphincter, which usually serves to prevent stomach acid and contents from rising into the esophagus this way. "Acid reflux and heartburn is what occurs if this sphincter is not working as it should," she explains. 

There are several variables she points to that can impact this happening, including muscle function at the base of the esophagus, excess movement of the intestines and the presence of a hiatal hernia. "Current research would suggest that genetics might also play a role in developing heartburn, though more studies are needed to gain a better understanding of this," she adds.

Other factors that cause or contribute to heartburn include eating habits, pregnancy, obesity (weight increases pressure on one's abdomen), and certain medications that list acid reflux as a potential side effect.

Most commonly, specific types of food increase the likelihood of irritation or cause the muscles at the base of the esophagus to relax. Some such foods include citrus fruits and fried foods, plus "carbonated beverages, mint, alcohol, and acidic or spicy foods," says Dr. Gregory Katz, a cardiologist at NYU Langone Health in New York City. 

Can heartburn be intermittent? 

Because dietary choices and lifestyle factors such as eating too quickly or lying down after eating can impact acid reflux, heartburn can be experienced intermittently, with symptoms and frequency varying from person to person. "Some people experience only minor heartburn symptoms...while other people can have more frequent heartburn with additional symptoms such as acid regurgitation and inflammation in the esophagus," says Bering. 

How to prevent heartburn

No matter how frequently one experiences it, there are several strategies for preventing heartburn. "Lifestyle changes such as stopping smoking, not wearing tight clothing, and sleeping with the head of your bed slightly elevated are a good place to start," advises Bering. 

Katz suggests minimizing alcohol consumption, avoiding large meals too close to bedtime, and losing weight, if necessary.

Bering similarly recommends healthy weight management and also suggests waiting a couple of hours after eating to lay down and to avoid any known dietary triggers of heartburn that you've experienced in the past. "And if symptoms persist, a doctor can rule out more worrisome conditions and may prescribe an antacid medication to help control symptoms," she says. 

More:Alka-Seltzer is the most commonly recommended medication for heartburn. Here's why.