Gas in the Digestive Tract National Digestive Diseases Information Clearinghouse What is gas? Gas is air in the digestive tract—the large, muscular tube that extends from the mouth to the anus, where the movement of muscles, U.S. Department along with the release of hormones and Esophagus of Health and Mouth Human Services enzymes, allows for the digestion of food. Gas leaves the body when people burp through the NATIONAL mouth or pass gas through the anus. INSTITUTES Stomach OF HEALTH Gas is primarily composed of carbon dioxide, oxygen, nitrogen, hydrogen, and sometimes methane. Flatus, gas passed through the anus, may also contain small amounts of Large gasses that contain sulfur. Flatus that intestine contains more sulfur gasses has more odor. Everyone has gas. However, many people think they burp or pass gas too often and that Small Colon they have too much gas. Having too much intestine (shaded) gas is rare. Anus Rectum What causes gas? Gas in the digestive tract is usually caused The digestive tract by swallowing air and by the breakdown of certain foods in the large intestine by bacteria. Burping allows some gas to leave the stomach. The remaining gas moves into the Everyone swallows a small amount of air small intestine, where it is partially absorbed. when eating and drinking. The amount of air A small amount travels into the large swallowed increases when people intestine for release through the anus. • eat or drink too fast The stomach and small intestine do not • smoke fully digest some carbohydrates—sugars, starches, and fiber found in many foods. • chew gum This undigested food passes through the • suck on hard candy small intestine to the large intestine. Once there, undigested carbohydrates are broken • drink carbonated or “fizzy” drinks down by bacteria in the large intestine, which • wear loose-fitting dentures release hydrogen and carbon dioxide in the process. Other types of bacteria in the large digest carbohydrates and the type of bacteria intestine take in hydrogen gas and create present in the intestines. methane gas or hydrogen sulfide, the most Some foods that may cause gas include common sulfur gas in flatus. • beans Studies have detected methane in the breath of 30 to 62 percent of healthy adults.1 A • vegetables such as broccoli, cauliflower, larger percentage of adults may produce cabbage, brussels sprouts, onions, methane in the intestines, but the levels may mushrooms, artichokes, and asparagus be too low to be detected. Research suggests • fruits such as pears, apples, and peaches that people with conditions that cause constipation are more likely to produce • whole grains such as whole wheat and detectable amounts of methane.1 More bran research is needed to find out the reasons • sodas; fruit drinks, especially apple for differences in methane production and juice and pear juice; and other drinks to explore the relationship between methane that contain high-fructose corn syrup, a and other health problems. sweetener made from corn Some of the gas produced in the intestines is • milk and milk products such as cheese, absorbed by the bloodstream and carried to ice cream, and yogurt the lungs, where it is released in the breath. • packaged foods—such as bread, cereal, Normally, few bacteria live in the small and salad dressing—that contain small intestine. Small intestinal bacterial amounts of lactose, a sugar found in overgrowth is an increase in the number of milk and foods made with milk bacteria or a change in the type of bacteria • sugar-free candies and gums that in the small intestine. These bacteria can contain sugar alcohols such as sorbitol, produce excess gas and may also cause mannitol, and xylitol diarrhea and weight loss. Small intestinal bacterial overgrowth is usually related to diseases or disorders that damage the What are the symptoms digestive system or affect how it works, of gas? such as Crohn’s disease—an inflammatory The most common symptoms of gas bowel disease that causes inflammation, or are burping, passing gas, bloating, and swelling, and irritation of any part of the abdominal pain or discomfort. However, not gastrointestinal (GI) tract—or diabetes. everyone experiences these symptoms. Which foods cause gas? Burping. Burping, or belching, once in a while, especially during and after meals, Most foods that contain carbohydrates can is normal. However, people who burp cause gas. In contrast, fats and proteins frequently may be swallowing too much air cause little gas. Foods that produce gas in and releasing it before the air enters the one person may not cause gas in someone stomach. else, depending on how well individuals Some people who burp frequently may have an upper GI disorder, such as 1Sahakian AB, Jee SR, Pimentel M. Methane and the gastroesophageal reflux disease—a chronic gastrointestinal tract. Digestive Diseases and Sciences. condition in which stomach contents flow 2010;55(8):2135–43. Epub 2009 Oct 15. 2 Gas in the Digestive Tract back up into the esophagus. People may Abdominal pain and discomfort. People believe that swallowing air and releasing it may feel abdominal pain or discomfort when will relieve the discomfort, and they may gas does not move through the intestines intentionally or unintentionally develop a normally. People with IBS may be more habit of burping to relieve discomfort. sensitive to gas and feel pain when gas is present in the intestines. Passing gas. Passing gas around 13 to 21 times a day is normal.2 Flatulence is excessive gas in the stomach or intestine that How is the cause of gas can cause bloating and flatus. Flatulence found? may be the result of problems digesting People can try to find the cause of gas on certain carbohydrates. their own by keeping a diary of what they eat Bloating. Bloating is a feeling of fullness and and drink and how often they burp, pass gas, swelling in the abdomen, the area between or have other symptoms. A diary may help the chest and hips. Problems digesting identify specific foods that cause gas. carbohydrates may cause increased gas and A health care provider should be consulted if bloating. However, bloating is not always caused by too much gas. Bloating may • symptoms of gas are bothersome result from diseases that affect how gas • symptoms change suddenly moves through the intestines, such as rapid gastric emptying, or from diseases that cause • new symptoms occur, especially in intestinal obstruction, such as colon cancer. people older than age 40 People who have had many operations, • gas is accompanied by other symptoms, internal hernias, or bands of internal scar such as constipation, diarrhea, or weight tissue called adhesions may experience loss bloating. The health care provider will ask about Disorders such as irritable bowel syndrome dietary habits and symptoms and may ask a (IBS) can affect how gas moves through person to keep a food diary. Careful review the intestines or increase pain sensitivity of diet and the amount of burping or gas in the intestines. IBS is a functional GI passed may help relate specific foods to disorder, meaning that the symptoms are symptoms and determine the severity of the caused by changes in how the digestive tract problem. Recording gas symptoms can help works. The most common symptoms of IBS determine whether the problem is too much are abdominal pain or discomfort, often gas in the intestines or increased sensitivity reported as cramping, along with diarrhea, to normal amounts of gas. constipation, or both. IBS may give a sensation of bloating because of increased If milk or milk products are causing gas, the sensitivity to normal amounts of gas. health care provider may perform blood or breath tests to check for lactose intolerance, Eating a lot of fatty food can delay stomach the inability or insufficient ability to digest emptying and cause bloating and discomfort, lactose. Lactose intolerance is caused by a but not necessarily too much gas. deficiency of the enzyme lactase, which is needed to digest lactose. The health care 2Gas-related complaints. The Merck Manuals provider may suggest avoiding milk products Online Medical Library. www.merckmanuals.com/ for a short time to see if symptoms improve. professional/sec02/ch008/ch008d.html. Updated October 2007. Accessed June 26, 2012. 3 Gas in the Digestive Tract The health care provider may perform a lacks to digest the sugar in beans and physical exam and order other types of many vegetables. The enzyme comes diagnostic tests, depending on a person’s in liquid and tablet form. Five drops symptoms. These tests can rule out serious are added per serving or one tablet is health problems that may cause gas or swallowed just before eating to break symptoms similar to those of gas. down the gas-producing sugars. Beano has no effect on gas caused by lactose or How is gas treated? fiber. Gas can be treated by reducing swallowed • Simethicone (Gas-X, Mylanta Gas) can air, making dietary changes, or taking over- relieve bloating and abdominal pain or the-counter or prescription medications. discomfort caused by gas. People who think they have too much gas can • Lactase tablets or drops can help people try to treat gas on their own before seeing a with lactose intolerance digest milk and health care provider. Health care providers milk products to reduce gas. Lactase can provide advice about reducing gas and tablets are taken just before eating prescribe medications that may help. foods that contain lactose; lactase drops Reducing swallowed air. Swallowing less air can be added to liquid milk products. may help reduce gas, especially for people Lactose-free and lactose-reduced milk who burp frequently. A health care provider and milk products are available at most may suggest eating more slowly, avoiding grocery stores.