Flatulence or gas can be annoying and embarrassing, but it is something that just about everyone has experienced to varying degrees. The good news is that you do not have to endure it. Well, at least not all the time.
What Causes Gas?
The first step toward lessening gas is learning what causes it. Most intestinal gas in healthy people results from bacterial fermentation in the colon, says gastroenterologist Satish Rao, MD. Complex carbohydrates are the cause of the rectal gas we pass. These include certain sugars, starch, and fiber.
"A normal diet contains a lot of carbohydrates that aren't digested by small bowel enzymes. Instead, they are dumped into the colon," Dr. Rao explains. "Between 15 and 30 grams of carbohydrates are dumped into the colon everyday, where they're digested by bacteria." This fermentation by bacteria gives off gas.
The meanest gas-producing carbohydrates, raffinose and stachyose, are found in beans. These include kidney beans, lima beans, black beans, navy beans, and soybeans.
Lactose, which is found mostly in milk and dairy products, can also cause excess gas in some people. People who do not have enough of the enzyme lactase, which digests lactose, experience gas. This condition, known as lactose intolerance, is much more common among people of Asian, Native American, and African decent, than among people of European decent.
The sugars fructose and sorbitol are also gas producers of the carbohydrate clan. Fructose is found in many fruits and vegetables. Sorbitol is found in fruits, including apples, peaches, and pears. Sorbitol is an artificial sweetener commonly used in sugar-free food products and candy.
Starches and Fiber
Aside from sugars, starch and fiber camp out in the colon too. Starches include potatoes, pasta, and rice. (Rice does not lead to gas, though.) Soluble fiber found in oat bran, beans, peas, and most fruits can also give off gas.
You probably knew that eating food causes gas, but what about eating air? "Air swallowing is one of the most common causes of gas, and it can be caused by eating quickly and taking in large amounts of air," says dietitian Lisa Andrews, MEd, RD.
However, swallowed air primarily escapes through belching, not through the rectum, says Dr. Rao.
Air swallowing can also be completely unrelated to eating. Other causes of swallowed air, according to gastroenterologists and dietitians, include the following:
What Makes Gas Smell?
Of all the gas we pass, researchers estimate that less than 1% smells. Odorless gas consists of nitrogen, oxygen, hydrogen, methane, and carbon dioxide. Researchers suspect that odorous gas consists of sulfur.
What Is a Normal Amount of Gas?
The average person passes gas 14 times a day. In fact, passing gas less than 25 times a day is normal, says Dr. Rao.
How to Reduce Gas
Andrews recommends taking these five steps towards freedom from flatulence:
Should I See a Doctor For My Gas?
If still experience excessive gas (25 or more episodes a day) after trying these tips, see your doctor. Although gas is a normal part of life, it can also be a sign of a gastrointestinal illness.
American Dietetic Association
American Gastroenterological Association
The Canadian Association of Gastroenterology
Dietitians of Canada
American Gastroenterological Association website. Available at: http://www.gastro.org. Accessed February 18, 2008.
Gas in the digestive tract. National Institute of Diabetes and Digestive and Kidney Diseases website. Available at: http://digestive.niddk.nih.gov/ddiseases/pubs/gas/. Published January 2008. Accessed December 19, 2011.
Preventing gas and flatulence. Harvard Medical School website. Available at: http://www.health.harvard.edu/press_releases/gas-flatulence. Accessed December 19, 2011.
Last reviewed December 2011 by Brian Randall, MD