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The Digestive System and Gas

What Is Gas?

Gas is a normal byproduct of the foods we eat. As the digestive system breaks food down, it produces gas, which is mainly composed of carbon dioxide, oxygen, nitrogen, hydrogen, and methane.

Usually, we eliminate gas through the mouth (burping) or through the anus (flatulance). We typically pass gas around 20 times a day. Gas is an ordinary occurrence, but its presence can be painful and socially embarrassing.

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What Causes Gas?

We produce gas in two ways: when we swallow air, and when the bacteria in the large intestine go to work helping to digest the food we eat.

Carbohydrates are especially troublesome. Humans cannot digest certain carbohydrates in the small intestine because we may not have (or not have enough of) the enzymes that can aid in their digestion. This food moves in the undigested state from the small intestine to the large intestine; it is here that the bacteria go to work, producing the gases hydrogen, carbon dioxide, and methane which are then expelled from the body.

Not everybody will suffer from gas from eating the same foods.

We also swallow a certain amount of air when we eat and drink. This contributes to the production of gas. We usually release swallowed air by burping it out. Whatever isn't released by burping goes into the small or large intestine, where it is eventually released as flatulence.

Which Foods Are Most Likely to Produce Gas?

You are most likely to experience gas by eating carbohydrates, which are found in such foods as beans, vegetables (especially broccoli, cabbage, and onions), fruits, dairy products, whole grain foods, soft drinks, and fruit drinks.

What Are the Symptoms of Gas?

In addition to burping and flatulence, people who have gas may feel bloated. They may also have pain in the abdomen, which they may mistake for another disease such as a heart attack or appendicitis.

Could Gas Be a Sign of a Medical Problem?

Yes. Chronic (long-lasting) belching may be a sign of disease in the upper digestive tract, such as ulcers or gastroesophageal reflux disease (GERD).

Bloating may be caused by a variety of diseases, including irritable bowel syndrome (IBS), colon cancer, and Crohn's disease or by a hernia.

How Are Gas-Related Illnesses Diagnosed?

Since diet is the main cause of gas, your health care provider will want to know about the foods you eat and your symptoms. He or she may ask you to keep a record of what you eat and drink to help identify offending foods. You may also be asked to keep track of how many times a day you pass gas.

You may have to eliminate certain foods from your diet. For example, if lactose intolerance (lactose is a type of sugar found in milk products) is suspected of causing the gas, you will probably have to limit your consumption of dairy products. 

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