THURSDAY, Jan. 5 (HealthDay News) -- Heartburn and acid reflux strike many people as an annoying and painful but ultimately harmless problem -- a result of overindulgence and gluttony that must be endured, much like a hangover after a night of drinking.

But frequent bouts of heartburn and reflux constitute a real medical condition known as gastroesophageal reflux disease, or GERD, and GERD is on the rise worldwide.

"The overall prevalence is increasing over the past decades," said Dr. Ronnie Fass, a medical advisory board member for the International Foundation for Functional Gastrointestinal Disorders who's also a professor of medicine at the University of Arizona and chief of gastroenterology at the Southern Arizona VA Health Care System.

The increase has occurred "not only in the United States, but in Asian countries, where GERD was unheard of," Fass said. "But we are the trailblazers. We are leading the world."

If left untreated, GERD can lead to bleeding or ulcers in the esophagus, a buildup of scar tissue that makes swallowing difficult and, in extreme cases, esophageal cancer, according to the U.S. National Institutes of Health.

"People consider heartburn part of the eating experience," Fass said. "They have to understand the presence of heartburn denotes a real medical problem."

Frequent reflux or heartburn are apparently a regular occurrence for Americans. "We believe up to 20 percent of the population experiences symptoms once a week, and 7 percent have daily symptoms," he said.

Heartburn and acid reflux occur when acidic digestive juices from the stomach get past a ring of muscle known as the lower esophageal sphincter, which acts as a valve separating the stomach from the esophagus.

People experience heartburn when the digestive juices eat away at the lining of the esophagus. Sometimes the acid refluxes all the way up through the esophagus to the mouth, causing people to taste digestive juices or food in the back of their mouth.

Doctors consider people to be suffering from GERD if they experience persistent reflux, meaning at least twice a week, according to the NIH. Anyone at any age can have GERD, although symptoms tend to be different for children 12 and younger, who may have asthma-like symptoms, a dry cough or difficulty swallowing.

Most of the time, GERD stems from one of two causes -- what you eat and how much you weigh -- but excessive weight is the most prominent, said Dr. Kenneth R. DeVault, chairman of the gastroenterology department at the Mayo Clinic in Jacksonville, Fla., and co-author of the American College of Gastroenterology's guidelines for treating GERD.

"The most consistent factor is probably weight gain and obesity," DeVault said. "It's become pretty clear that a small amount of weight gain produces an increase in reflux symptoms. I'm not talking a large amount; I'm talking about 5 or 10 pounds, probably. Even if you're already overweight, increasing your weight will increase your risk of reflux over the next several months."

Excess weight can press on the stomach, forcing acid past the valve into the esophagus. And, as Fass explained, the problem isn't just the belly flab evident on people who are obese or overweight. Rather, the accumulation of fat around the organs inside the body contributes by increasing pressure on the stomach, making reflux much more likely to occur, he said.

GERD also can be caused, or exacerbated, by a person's diet. But foods contribute to reflux in different ways.

Caffeine, for example, has been shown to relax the esophageal sphincter, increasing the chances of reflux, DeVault said.

Eating fatty foods can also contribute to reflux because fats slow the emptying of the stomach, meaning "there's more material left in the stomach that can be refluxed," he said.

Acidic, spicy or strongly flavored foods also can contribute to reflux by increasing the amount of acid in the stomach, according to the NIH. Citrus fruits or juices, tomatoes, mint, garlic, onions and chocolate are among the main offenders.

Also, lifestyle changes can usually reduce the possibility of reflux, the two experts said. These include:

• Making a concerted effort to lose weight, by exercising and adopting a healthy diet.
• Learning which foods are more likely to trigger excess acid or reflux, and then avoiding them.
• Eating the final meal of the day two to three hours before bedtime, thus reducing the amount of food in the stomach that would press against the esophageal valve.
• Elevating the head of the bed, if nighttime reflux is a problem, as this can reduce the pressure of stomach acid and contents on the valve.

If reflux symptoms persist, however, DeVault stressed that more needs to be done to avoid damage to the esophagus.

"If they have frequent heartburn symptoms, more than weekly, and have had it for many years, they need to see a physician," he said.

More information

The U.S. National Institute of Diabetes and Digestive and Kidney Diseases has more on GERD.

For more on the effects of GERD, read about one woman's story.