What goes up must come down.

But for the millions of Americans who suffer from gastroesophageal reflux disease, or GERD, that saying is of little comfort.

Commonly referred to as acid reflux, this annoying condition is usually accompanied by symptoms of heartburn and/or regurgitation, which can make for an irritating lifestyle.

“Acid reflux occurs when the acidic contents of the stomach pass up into the esophagus, and the sphincter muscle –- the barrier between the two –- has a defect, so it cannot block the acid,” Dr. Anish Sheth, a gastroenterologist and professor of medicine at Yale University, told FOXNews.com. “The lining of the esophagus is not made to resist acid, it’s very different from the stomach. So acid reflux can cause ulcers and inflammation, and a whole host of other problems.”

Acid reflux can present itself with a variety of other symptoms. A chronic cough, worsening of asthma symptoms, constant throat clearing and a hoarse voice are all problems that patients with acid reflux have complained of.

1. Who is at risk for acid reflux?

There is really no rhyme or reason as to why acid reflux occurs, Sheth said, and it afflicts millions of people in the United States. Except for obese people, there aren’t any demographics for who are more at risk, he said.

“There are certain lifestyle things we tell people to avoid,” he said. “Alcohol consumption increases the risk of acid reflux, as well as caffeine. So do foods like chocolates and tomatoes, or tomato-based products. If you have mild symptoms, and can avoid these things, you might be able to avoid medicines.”

2. How is acid reflux diagnosed?

A new outpatient procedure allows the doctor to attach a capsule to the patient’s esophagus using an endoscopy, which involves sticking a tube down the patient's throat. The capsule transmits wireless pH data to a beeper on the patient’s belt over the course of 48 hours, to give doctors a concise idea of how much acid is being washed up.

3. How is acid reflux treated?

There are three ways to treat acid reflux, Sheth said:

1. Lifestyle changes, which include adjusting your dietary habits and losing weight if you are obese;

2. Taking proton pump inhibitors, which are acid-reducing medicines like Nexium, Prilosec or Protonix;

3. Surgery. This is usually a last resort taken after medication and dietary changes fail. The procedure involves wrapping the top portion of the stomach around the bottom of the esophagus and securing it below the diaphragm.

By creating a tight sphincter, the food cannot reflux back into the esophagus.

4. Acid-reflux may cause other medical conditions

“The thing that should be taken away, is that acid reflux isn’t going to kill you,” Sheth said. “Why we actually look down your throat into your esophagus with a scope is because it can cause other problematic conditions.”

If left untreated, acid reflux can cause:

— Barrett’s esophagus. The cells that line the esophagus undergo a change, Sheth said. In a small percentage of patients, they can turn pre-cancerous; dysplastic, which is the earliest form of a cancerous lesion; or cancerous.

— Esophageal stricture. This is a narrowing in the esophagus that comes after a long period of irritation and leads to difficulty in swallowing, Sheth said.

— Esophageal cancer. If doctors can catch it early enough, surgery is still an option and patients have good outcomes, Sheth said. If patients wait until they have trouble swallowing, chances are the cancer is at a more advanced stage, and treatment could be less effective.