Flatulence Patient Information Fact Sheet

What is flatulence?
Otherwise known as gas, more than 90% of flatus is made up of five gases: nitrogen (the main component of air), oxygen, carbon dioxide, hydrogen and methane. The remaining 10% is comprised of a small amount of other gases. Gas is produced in the gut, a muscular tube stretching from the esophagus to the rectum that is about 40 feet long if stretched out. People usually produce about 1–3 pints of gas every day and pass this gas through the rectum as flatus.

What causes flatulence?
The nitrogen and oxygen come from swallowed air; the carbon dioxide is produced by the interaction of stomach acid and the bicarbonate in bile and pancreatic juices. These gases get into the small intestine where most of the oxygen and carbon dioxide are absorbed into the blood stream; the nitrogen is passed down to the large bowel. The small intestine is where the food we eat is digested and absorbed; the residues, such as dietary fiber and some carbohydrates, pass on to the large bowel. The colon acts as a gas works. It contains a huge population of many different kinds of bacteria, which are essential to good health and which ferment the residues delivered from the small intestine, producing large volumes of hydrogen, methane, carbon dioxide and other gases in the process. Most of these gases are absorbed into the blood stream and eventually excreted in the breath; the rest is passed as flatus.

Common forms of gas
Belching, burping or flatulence Every time we swallow we take some air into the stomach. A belch is an involuntary expulsion of gas by the stomach when it becomes distended from an excess of swallowed air. Eating rapidly or gulping food and drink, drinking a lot of liquid with meals, chewing gum, smoking, or wearing loose dentures promote air swallowing. Some people swallow saliva to relieve heartburn and swallow air at the same time. Other people swallow air without noticing it, especially when they are tense. Fizzy drinks like beer cause belching because they produce gas (carbon dioxide) in the stomach.

Chronic or repetitive burping (aerophagy) In this case, air is not swallowed into the stomach but sucked into the esophagus and rapidly expelled. Repetitive belching like this can last for minutes at a time and is very embarrassing. It is nearly always due to stress or anxiety. There is no medical treatment, and the cure lies in realizing the cause. Air cannot be sucked in when the jaws are separated, so repetitive belching can be temporarily controlled by firmly clenching something like a pencil between the teeth. Some people develop aerophagy because of discomfort in the chest. If you develop belching associated with chest discomfort—especially discomfort associated with exertion—or if you have difficulties in swallowing, you should seek medical help promptly.