font size

Intestinal Gas (Belching, Bloating, Flatulence) (cont.)

Medical Author:
Medical Editor:

What causes flatulence (gas)?

Flatulence, also known as farting, is the act of passing intestinal gas from the anus. Gas in the gastrointestinal tract has only two sources. It is either swallowed air or is produced by bacteria that normally inhabit the intestines, primarily the colon. Swallowed air rarely is the cause of excessive flatulence.

The usual source of excessive gas is intestinal bacteria. The bacteria produce the gas (primarily hydrogen and/or methane) when they digest foods, primarily sugars and nondigestible polysaccharides (for example, starch, cellulose), that have not been digested during passage through the small intestine. The bacteria also produce carbon dioxide, but the carbon dioxide is so rapidly absorbed from the intestine that very little passes in flatus.

Sugars

Sugars that are commonly digested poorly (maldigested) and malabsorbed are lactose, sorbitol, and fructose.

  • Lactose is the sugar in milk. The absence of the enzyme lactase in the lining of the intestines, which is a genetic trait, causes the maldigestion. Lactase is important because it breaks apart the lactose so that it can be absorbed.
  • Sorbitol is a commonly used sweetener in low calorie foods.
  • Fructose, primarily as high fructose corn syrup, is a commonly used sweetener in all types of candies and drinks.

Polysaccharides

Starches are another common source of intestinal gas. Starches are polysaccharides that are produced by plants and are composed of long chains of sugars, primarily fructose. Common sources of different types of starch include wheat, oats, potatoes, corn, and rice.

  • Rice is the most easily digested starch, and little undigested rice starch reaches the colon and the colonic bacteria. Accordingly, the consumption of rice produces little gas.
  • In contrast, some of the starches in wheat, oats, potatoes, and, to a lesser extent, corn, all may reach the colon. These starches, therefore, may result in the production of appreciable amounts of gas.
  • The starch in whole grains produces more gas than the starch in refined (purified) grains. Thus, more gas is formed after eating foods made with whole wheat flour than with refined wheat flour. This difference in gas production probably occurs because of the fiber (similar to a complex starch) present in the whole grain flour. Much of this fiber is removed during the processing of whole grains into refined flour.
  • Finally, certain fruits and vegetables, for example, beans and cabbage, also contain poorly digested starches that reach the colon and are easily converted by bacteria into gas.
  • Most vegetables and fruits contain cellulose, another type of polysaccharide that is not digested at all as it passes through the small intestine. However, unlike sugars and other starches, cellulose is used only very slowly by colonic bacteria. Therefore, the production of gas after the consumption of fruits and vegetables usually is not great unless the fruits and vegetables also contain sugars or polysaccharides other than cellulose.

Small amounts of air are continuously being swallowed and bacteria are constantly producing gas. Contractions of the intestinal muscles normally propel the gas through the intestines and cause the gas to be expelled. Flatulence (passing intestinal gas) prevents gas from accumulating in the intestines.

However, there are two other ways in which gas can escape the intestine.

  • First, it can be absorbed across the lining of the intestine into the blood. The gas then travels in the blood and ultimately is excreted in the breath.
  • Second, gas can be removed and used by certain types of bacteria within the intestine. In fact, most of the gas that is formed by bacteria in the intestines is removed by other bacteria in the intestines. (Thank goodness!)
Medically Reviewed by a Doctor on 2/28/2014

Patient Comments

Viewers share their comments

Intestinal Gas - Effective Treatments Question: What kinds of treatments have been effective for your intestinal gas?
Intestinal Gas - Causes Question: What was the cause of your intestinal gas?
Intestinal Gas - Bloating Causes Question: For some, it's eating a certain food. What is the usual cause of your bloating (intestinal gas)?
Intestinal Gas - Flatulence Causes Question: It may be embarrassing, but what is often the cause of your flatulence (intestinal gas)?
Source: MedicineNet.com
http://www.medicinenet.com/intestinal_gas_belching_bloating_flatulence/article.htm

GI Disorders

Get the latest treatment options.

Intestinal Gas (Belching, Bloating, Flatulence) Related Articles
advertisement
advertisement
Use Pill Finder Find it Now See Interactions

Pill Identifier on RxList

  • quick, easy,
    pill identification

Find a Local Pharmacy

  • including 24 hour, pharmacies

Interaction Checker

  • Check potential drug interactions
Search the Medical Dictionary for Health Definitions & Medical Abbreviations

NIH talks about Ebola on WebMD