Most people will feel the “burn” of heartburn at some point. But if you have gastroesophageal reflux disease, or GERD, it’s more than an occasional discomfort.

"While most people think that reflux occurs because of an overproduction in stomach acid, it’s actually the contrary—it’s having low amounts of stomach acid that leads to this problem,” claims

How does low stomach acid cause reflux? Mercola doesn’t say.

“There’s no data to support that theory,” says Scott Gabbard, a gastroenterologist at the Cleveland Clinic. “Reflux isn’t an acid problem. It’s a valve problem.”

What causes reflux

That problem: a valve called the lower esophageal sphincter (LES), to be precise. It’s the junction between your esophagus and your stomach.

“It’s a ring of muscle that’s supposed to open when you swallow and then close,” Gabbard explains.

“If that valve opens when it’s not supposed to, you’ve got an open conduit for stomach contents to come back up into the esophagus.”

That’s reflux. It happens to everyone occasionally. Most of us don’t even feel it.

“But if the reflux becomes troublesome with symptoms like frequent heartburn, sour taste in the mouth, or regurgitation, we call it gastroesophageal reflux disease,” says Carolyn Newberry, a gastroenterologist and assistant professor of medicine at Weill Cornell Medical College.

And that’s not rare. “Around 20 percent of American adults have GERD symptoms on a weekly basis,” says Joel Rubenstein, research scientist at the Veterans Affairs Center for Clinical Management Research and director of the Barrett’s Esophagus Program at the University of Michigan Medical School.

What causes the lower esophageal sphincter to relax?

In some cases, drugs like beta-agonists for asthma, calcium channel blockers for blood pressure, and benzodiazepines for anxiety may be to blame.

“And having elevated weight can do it,” notes Gabbard. “Excess fat increases pressure in the abdomen, and it may actually have some hormonal effects that cause the sphincter to relax.”

The consequences of GERD

“The vast majority of people who have GERD will not have any long-term consequences,” says Rubenstein. But regularly bathing the esophagus in corrosive stomach acid can lead to serious complications in some people.

“People can develop esophagitis, which is inflammation in the esophagus,” says Newberry. In some cases, that can lead to esophageal ulcers.

Over time, acid exposure can cause the cells that normally line the esophagus to be replaced with cells that resemble the acid-resistant cells of the intestine. That condition—Barrett’s esophagus—occurs in roughly 15 percent of people with GERD.

Barrett’s has no symptoms, and it can lead to a deadly cancer.

“People with Barrett’s have an estimated lifetime risk of esophageal adenocarcinoma of about 5 to 10 percent,” says Rubenstein. “And the fatality rate for adenocarcinoma is very high.” Most patients live for less than a year.

“Many people aren’t diagnosed until that cancer is late stage,” notes Rubenstein. “Most patients with Barrett’s will not progress to cancer. But we do endoscopies to identify those who will. Those who are screened tend to be diagnosed with an earlier-stage cancer and have better survival.”