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What I Need to Know About Gas

July 31, 2013

Table of Contents

The digestive tract

The digestive tract

What Is Gas?

Gas is air in the digestive tract. Gas leaves the body when people burp through the mouth or pass gas through the anus* -- the opening at the end of the digestive tract where stool leaves the body.

Everyone has gas. Burping and passing gas are normal. Many people believe that they burp or pass gas too often and that they have too much gas. Having too much gas is rare.

What Causes Gas?

Gas in the digestive tract is usually caused by swallowing air and the breakdown of certain foods in the large intestine.

*See the Pronunciation Guide for tips on how to say the underlined words.

You typically swallow a small amount of air when you eat and drink. You swallow more air when you

What Causes Gas?

Some of the air you swallow leaves the stomach through the mouth when you burp. Some swallowed air is absorbed in the small intestine. Some air moves through the small intestine to the large intestine and is passed through the anus.

The stomach and small intestine do not fully digest all of the food you eat. Undigested carbohydrates -- sugars, starches, and fiber found in many foods -- pass through to the large intestine. Bacteria in the large intestine break down undigested carbohydrates and release gas. This gas is passed through the anus.

Normally, few bacteria live in the small intestine. Small intestinal bacterial overgrowth (SIBO) is an increase in the number of bacteria or a change in the type of bacteria in the small intestine. These bacteria can produce excess gas and may also cause diarrhea and weight loss. SIBO is usually related to diseases or disorders that damage the digestive system or affect how it works, such as Crohn's disease or diabetes.

Which Foods Cause Gas?

Which Foods Cause Gas?

Most foods that contain carbohydrates can cause gas. Foods that cause gas for one person may not cause gas for someone else. Some foods that contain carbohydrates and may cause gas are

What Are the Symptoms of Gas?

The most common symptoms of gas are:

Which Foods Cause Gas?

How Is the Cause of Gas Found?

You can try to find the cause of gas by keeping a diary of what you eat and drink and how often you burp, pass gas, or have other symptoms. The diary may help you identify the foods that cause you to have gas.

Talk with your health care provider if

Your health care provider will ask about your diet and symptoms. Your health care provider may review your diary to see if specific foods are causing gas.

If milk or milk products are causing gas, your health care provider may perform blood or breath tests to check for lactose intolerance. Lactose intolerance means you have trouble digesting lactose. Your health care provider may ask you to avoid milk and milk products for a short time to see if your gas symptoms improve.

Your health care provider may test for other digestive problems, depending on your symptoms.

How Is Gas Treated?

How Is Gas Treated?

You can try to treat gas on your own, before seeing your health care provider, if you think you have too much.

Swallowing less air and changing what you eat can help prevent or reduce gas. Try the following tips:

Some over-the-counter medicines can help reduce gas:

Your health care provider may prescribe medicine to help relieve gas, especially if you have SIBO or IBS.

Eating, Diet, and Nutrition

Your eating habits and diet affect the amount of gas you have. For example, eating and drinking too fast can cause you to swallow more air. And you may have more gas after you eat certain carbohydrates.

Track what you eat and your gas symptoms to find out what foods cause you to have more gas. Avoid or eat less of the foods that cause your gas symptoms.

Points to Remember

Hope Through Research

The National Institute of Diabetes and Digestive and Kidney Diseases' (NIDDK's) Division of Digestive Diseases and Nutrition supports research into digestive conditions, including gas. Researchers are studying new treatments for gas and for IBS, a disorder in which people may have gas along with other symptoms.

Participants in clinical trials can play a more active role in their own health care, gain access to new research treatments before they are widely available, and help others by contributing to medical research. For information about current studies, visit

Pronunciation Guide

abdomen (AB-doh-men)

anus (AY-nuhss)

carbohydrates (KAR-boh-HY-drayts)

constipation (KON-stih-PAY-shuhn)

diarrhea (DY-uh-REE-uh)

fructose (FROOK-tohss)

intestine (in-TESS-tin)

irritable bowel syndrome (IHR-ih-tuh-buhl) (boul) (SIN-drohm)

lactose (LAK-tohss)

lactose intolerance (LAK-tohss) (in-TOL-ur-uhnss)

mannitol (MAN-ih-tol)

simethicone (sih-METH-ih-kohn)

sorbitol (SOR-bih-tol)

xylitol (ZY-lih-tol)

For More Information

American College of Gastroenterology
P.O. Box 342260
Bethesda, MD 20827–2260
Phone: 301–263–9000

American Dietetic Association
120 South Riverside Plaza, Suite 2000
Chicago, IL 60606–6995

American Gastroenterological Association
4930 Del Ray Avenue
Bethesda, MD 20814
Phone: 301–654–2055
Fax: 301–654–5920

This article was provided by National Digestive Diseases Information Clearinghouse. You can find this article online by typing this address into your Web browser:

General Disclaimer: is designed for educational purposes only and is not engaged in rendering medical advice or professional services. The information provided through should not be used for diagnosing or treating a health problem or a disease. It is not a substitute for professional care. If you have or suspect you may have a health problem, consult your health care provider.