Under normal circumstances, a person produces up to four pints of gas a day, and passes gas up to 20 times a day. How is that possible, you say, if those people aren’t always eating foods like beans, cabbage, and broccoli?

The answer is because excess gas can be made in myriad ways. That’s why up to 20 percent of the population complains about having excessive gas that causes frequent belching and flatulence.

Upper Intestinal Gas

One of the most common sources of upper intestinal gas is swallowed air. The medical term for swallowed air is aerophagia. Swallowed air contains nitrogen, oxygen, and carbon dioxide. Too much swallowed air can lead to bloating and belching. Here are some ways that air gets inside you:

Eating or drinking too fast
Chewing gum
Smoking
Loose dentures
Drinking through a straw

Another unusual cause of bloating is continuous positive airway pressure therapy (CPAP) machines. CPAP is one of the most common treatments for sleep apnea. A CPAP machine forces air into the throat during sleep, and some of this air goes into the stomach. If you have bloating and you use CPAP, talk to your sleep specialist. In many cases, bloating can be avoided by changing the settings on the machine.

Lower Intestinal Gas

The other way that gas gets into your digestive system is through the breakdown of undigested foods in your large intestine by bacteria that normally live there. This gas, made up of hydrogen, carbon dioxide, and in some people, methane, has nowhere to go but out through the anus. The technical term for this gas is flatus.

We are all familiar with flatus caused by beans or cabbage, but here are some less known flatus producers:

Starches like potatoes, corn, and pasta
Fruits like apples, peaches, and pears
Vegetables like onions, artichokes, and asparagus
Spicy, fried, and fatty foods

A bit of trivia: The only starch that produces no gas is rice.

Stomach and Intestinal Problems

From stomach problems to colon problems, anything that interferes with the normal digestion of food can lead to excess gas in the system. Here are some common issues that can interfere with digestion:

Gastritis. This condition refers to anything that cases the lining of your stomach to get swollen and irritated. It could be an ulcer caused by bacteria, a reaction to medication, or too much stomach acid. Symptoms of this upper intestinal gas situation include bloating, belching, nausea and vomiting.
Lactose intolerance. Lactose is a natural sugar found in dairy products. In order to digest this sugar you need an enzyme called lactase, and some people don't have enough. Low levels of lactase are common in people of African, Asian, and Native American descent. Symptoms of lactose intolerance include excessive gas and bloating.
Celiac disease. This is an inherited disorder in which people cannot tolerate the protein found in wheat products (gluten). The disease affects digestion in the upper part of the intestine and leads to intestinal gas, bloating, and pain.
Irritable bowel syndrome (IBS). What causes IBS is not known, but it’s frequently the reason for complaints of bloating. The bloating may be due to abnormal movements of the digestive muscles or it may be due to an oversensitivity that causes normal amounts of intestinal gas to feel uncomfortable or painful.

When gas symptoms are accompanied by other symptoms like pain, vomiting, constipation, cramps, heartburn, bleeding, or weight loss, you need to see your doctor right away.

Intestinal gas and occasional bloating are usually a normal part of the digestive process. In most cases, excess gas is caused by swallowing too much air or eating gas-producing foods. This kind of gas can usually be controlled by being more careful about how and what you eat. Talk to your doctor if you think your gas symptoms are excessive. There are medications that can help.

Surprising Causes of Excessive Gas