What I need to know about

Gas

National Digestive Diseases 

Information Clearinghouse

What I need to know about 

Gas 
Contents

What is gas? ............................................................. 1

What causes gas?..................................................... 1

Which foods cause gas? .......................................... 3

What are the symptoms of gas? ............................. 5

How is the cause of gas found?.............................. 6

How is gas treated? ................................................. 8

Eating, Diet, and Nutrition .................................. 10

Points to Remember ............................................. 10

Hope through Research ....................................... 11

Pronunciation Guide............................................. 12

For More Information .......................................... 13

Acknowledgments ................................................. 14
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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. 

*See page 12 for tips on how to say the words in 

bold type. 

What causes gas? 

Gas in the digestive 

tract is usually caused 

by swallowing air and 

the breakdown of 

certain foods in the 

large intestine. 

Anus 

Esophagus 

Stomach 

Colon 

(shaded) Small 

intestine 

Mouth 

Rectum 

Large 

intestine 

The digestive tract 

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You typically swallow a small amount of air when 

you eat and drink. You swallow more air when you 

● eat or drink too fast 

● smoke 

● chew gum 

● suck on hard candy 

● drink carbonated or “fizzy” drinks 

● wear loose-fitting dentures 

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. 

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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? 

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 

● beans 

●	 vegetables such as broccoli, cauliflower, cabbage, 

brussels sprouts, onions, mushrooms, artichokes, 

and asparagus 

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4

● fruits such as pears, apples, and peaches

● whole grains such as whole wheat and bran

● sodas; fruit drinks, especially apple juice and 

pear juice; and other drinks that contain high 

fructose corn syrup, a sweetener made from corn

● milk and milk products such as cheese, ice 

cream, and yogurt

● packaged foods—such as bread, cereal, and 

salad dressing—that contain small amounts of 

lactose, the sugar found in milk and foods made 

with milk

● sugar-free candies and gums that contain sugar 

alcohols such as sorbitol, mannitol, and xylitol
What are the symptoms of gas? 

The most common symptoms of gas are: 

 

 

 

 

 

 

 

 

 

 

● Burping. Burping once in awhile, especially 

during and after meals, is normal. If you burp 

very often, you may be swallowing too much air. 

Some people with digestive problems swallow air 

on purpose and burp because they believe it will 

help them feel better. 

●	 Passing gas. Passing gas around 13 to 21 times 

a day is normal. If you think you pass gas more 

often than that, you may have trouble digesting 

certain carbohydrates. 

●	 Bloating. Bloating is a feeling of fullness and 

swelling in the abdomen, the area between the 

chest and hips. Disorders such as irritable 

bowel syndrome (IBS) can affect how gas moves 

through the intestines. If gas moves through 

your intestines too slowly, you may feel bloated. 

●	 Abdominal pain or discomfort. People may feel 

abdominal pain or discomfort when gas does not 

move through the intestines normally. People 

with IBS may be more sensitive to gas in the 

intestines. 

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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 

●	 gas symptoms often bother you 

●	 your symptoms change suddenly 

●	 you have new symptoms, especially if you are 

older than age 40 

●	 you have other symptoms—such as constipation, 

diarrhea, or weight loss—along with gas 

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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. 

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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: 

●	 Eat more slowly. 

●	 If you smoke, quit or cut down. 

●	 If you wear dentures, see your dentist and make 

sure your dentures fit correctly. 

●	 Don’t chew gum or suck on hard candies. 

●	 Avoid carbonated drinks, such as soda and beer. 

●	 Drink less fruit juice, especially apple juice and 

pear juice. 

●	 Avoid or eat less of the foods that cause you to 

have gas. 

8 
 

 

 

Some over-the-counter medicines can help 

reduce gas: 

●	 Taking alpha-galactosidase (Beano) when you 

eat beans, vegetables, and whole grains can 

reduce gas. 

●	 Simethicone (Gas-X, Mylanta Gas) can relieve 

bloating and abdominal pain or discomfort 

caused by gas. 

●	 If you are lactose intolerant, lactase tablets or 

liquid drops can help you digest milk and milk 

products. You can also find lactose-free and 

lactose-reduced milk and milk products at the 

grocery store. 

Your health care provider may prescribe medicine 

to help relieve gas, especially if you have SIBO 

or IBS. 

9 
 

 

 

 

 

 

 

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 

●	 Gas is air in the digestive tract. 

●	 Everyone has gas. Burping and passing gas are 

normal. 

●	 Gas in the digestive tract is usually caused by 

swallowing air and the breakdown of certain 

foods in the large intestine. 

●	 Most foods that contain carbohydrates can 

cause gas. 

●	 Foods that cause gas for one person may not 

cause gas for someone else. 

10
 

 

 

 

 

 

 

 

 

 

 

 

 

●	 The most common symptoms of gas are burping, 

passing gas, bloating, and abdominal pain or 

discomfort. 

●	 Swallowing less air and changing what you eat 

can help prevent or reduce gas. 

●	 Some over-the-counter medicines can help 

reduce gas. 

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 www.ClinicalTrials.gov.

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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)

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For More Information 

American College of Gastroenterology 

P.O. Box 342260

Bethesda, MD 20827–2260

Phone: 301–263–9000

Internet: www.acg.gi.org 

American Dietetic Association 

120 South Riverside Plaza, Suite 2000 

Chicago, IL 60606–6995 

Internet: www.eatright.org 

American Gastroenterological Association 

4930 Del Ray Avenue 

Bethesda, MD 20814 

Phone: 301–654–2055 

Fax: 301–654–5920 

Email: member@gastro.org 

Internet: www.gastro.org 

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Acknowledgments 

Publications produced by the Clearinghouse are 

carefully reviewed by both NIDDK scientists and 

outside experts. This publication was reviewed by 

Charlene M. Prather, M.D., M.P.H., Saint Louis 

University. 

The U.S. Government does not endorse or favor any specific 

commercial product or company. Trade, proprietary, or company 

names appearing in this document are used only because they are 

considered necessary in the context of the information provided. 

If a product is not mentioned, the omission does not mean or imply 

that the product is unsatisfactory. 

14
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This publication is not copyrighted. The Clearinghouse 

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This publication is available at www.digestive.niddk.nih.gov.

This publication may contain information about medications. 

When prepared, this publication included the most current 

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information. 
NIH Publication No. 12–4156

October 2011

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