More Than You Ever Wanted to Know About Flatulence

Why it happens

It is normal to have some air in the digestive tract; some gets there when you swallow it, and some is produced by digestion. It is also normal for the body to periodically get rid of it. Passing gas out the rectum helps to keep the pressure within the intestinal tract low and prevents painful stretching of the stomach and the intestine.  Burping accomplishes the same thing. On average, people pass gas 14 times a day, either consciously or unconsciously, and the body produces about two liters of flatus (the technical name for intestinal gas) every day.

To understand why flatulence happens, you have to understand a little bit about the digestive process. The stomach and intestines move food along by a process called peristalsis. The tubelike intestines squeeze in an organized, sequential fashion to keep food and waste products moving along toward the anus. Any air in the intestines gets pushed along, too, and eventually it needs to be expelled.

That process is often accompanied by noise, a foul smell or both. Depending on the situation, flatulence may be embarrassing or inappropriate. Luckily, most of the time, you can control when you pass gas. Nerves in the rectum send a signal to the brain when it feels the pressure of a bowel movement or gas that needs to exit the body. If the brain receives the message at an inconvenient time, you can consciously contract the external anal sphincter to keep the anus closed, and the gas or bowel movement in. 

Why do some foods cause gas?

We all know that some foods cause more gas than others. Beans always top the list. Others include:

• Certain vegetables, including cabbage, Brussels sprouts, broccoli, cauliflower and peas
• Oat bran and other high-fiber foods
• Carbonated beverages
• Foods containing sorbitol, an artificial sweetener used in many low-calorie foods
• Fructose, a natural sugar present in many fruits (including prunes, pears, grapes, dates and figs) and in many sweeteners
  

These foods cause gas because they do not break down until they reach the large intestine, where they are digested by bacteria. This process creates more gas than digestion that occurs in the small intestine.

What makes it smell bad?

Once again, you can blame the bacteria in the large intestine. They produce the foul-smelling gas when they ferment undigested foods that have not been absorbed in the small intestine. The gases include methane and hydrogen sulfide, which smells like rotten eggs. The worst odor is related to strong-smelling sulfur, which makes up just 1 percent of flatus.

Men versus women

If you go by movies and television, you’d guess that men pass gas more often than women – remember the flatulent cowboys in Blazing Saddles? However, it’s not clear that men are gassier than women. Genes and diet—not gender—probably play the largest roles in how much gas a person produces.

What you can do about it

Since passing gas is a natural part of digestion, there’s nothing you can do to prevent it. But if you have excessive gas that is causing embarrassment, here are some tips. The simplest are figuring out which foods cause gas for you and avoiding them. Also make sure to eat and drink slowly—speed eating makes you swallow more gas. Over-the-counter and prescription medications can also help, but talk to your doctor or pharmacist if you want to try one of those.

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