Flatulence

Flatulence is the release of a mixture of gases known as flatus produced by symbiotic bacteria and yeasts living in the gastrointestinal tract of mammals. Flatus is released under pressure through the anus, often accompanied by odor and sound. Releasing flatus gases is known as farting in colloquial English.

Explanation

The average human releases 0.5 to 1.5 litres (1 to 3 U.S. pints) (measured at NTP) of flatus a day by flatulating 12 to 25 timesLevitt MD, Bond JH. "Volume, composition, and source of intestinal gas." Gastroenterology. 1970;59:921-928.Levitt MD. "Volume and composition of human intestinal gas determined by means of an intestinal washout technique." N Engl J Med. 1971;284:1394-1398.Levitt MD, Lasser RB, Schwartz JE, et al. "Studies of a flatulent patient." N Engl J Med. 1976;295:260-262.. The primary constituents of flatulence are the non-odorous gases nitrogen (ingested), carbon dioxide (produced by aerobic microbes or ingested), and hydrogen (produced by some microbes and consumed by others), as well as lesser amounts of oxygen (ingested) and methane (produced by anaerobic microbes)Suarez F, Furne J, Springfield J, Levitt M. "Insights into human colonic physiology obtained from the study of flatus composition." Am J Physiol. 1997;272(5 Pt 1):G1028-33.. Odors result from trace amounts of other components (often containing sulphur, see below).

Composition of flatus gases

Nitrogen is the primary gas released. Methane and hydrogen, lesser components, are flammable, and so flatulence is susceptible to catching fire. Not all humans produce flatus that contains methane. For example, in one study of the feces of nine adults, only five of the samples contained bacteria capable of producing methaneMiller TL, Wolin MJ, de Macario EC, Macario AJ. "Isolation of Methanobrevibacter smithii from human feces." Appl Environ Microbiol. 1982;43(1):227-232.. Similar results are found in samples of gas obtained from within the rectum. The gas released during a flatus event frequently has a foul odor which mainly results from low molecular weight fatty acids such as butyric acid (rancid butter smell) and reduced sulfur compounds such as hydrogen sulfide (rotten egg smell) and carbonyl sulfide that are the result of protein breakdown. The incidence of odoriferous compounds in flatus increases from herbivores, such as cattle, to omnivores to carnivorous species, such as cats. Flatulence odor can also occur when there is a number of bacteria and/or feces in the anus while being expelled. A small amount of solid or liquid fecal matter in fine particulate aerosol form may also be expelled, and included, along with flatulence.

Causes

Intestinal gas is composed of 90% exogenous sources (air that is ingested through the nose and mouth) and 10% endogenous sources (gas produced within the digestive tract). The exogenous gases are swallowed (aerophagia) when eating or drinking or during times of excessive salivation (as might occur when nauseated or as the result of gastroesophageal reflux disease). The endogenous gases are produced as a by-product of digesting certain types of food.

Flatulence producing foods are typically high in polysaccharides (especially oligosaccharides such as inulin) and include beans, lentils, milk, onions, radish, sweet potatoes, cheese, cashews, broccoli, cabbage, Jerusalem artichokes, oats, yeast in breads, etc. In beans, endogenous gases seem to arise from oligosaccharides, carbohydrates that are resistant to digestion. These pass through the upper intestine largely unchanged, and when they reach the lower intestine, bacteria feed on them, producing copious amounts of flatus (McGee 1984 pp.257–8).In the case of those with lactose intolerance, intestinal bacteria feeding on lactose can give rise to excessive gas production when milk or lactose-containing substances have been consumed.

Interest in the causes of flatulence was spurred by high-altitude flight and the space program; the low atmospheric pressure, confined conditions, and stresses peculiar to those endeavours were cause for concern (McGee, 1984 pp.257–8).

Mechanism of action

The noises commonly associated with flatulence are caused by the vibration of the anus. The sound varies depending on the tightness of the sphincter muscle and velocity of the gas being propelled, as well as other factors such as moisture and body fat. The pitch of the flatulence outburst can also be affected by the anal embouchure. Among humans, sometimes farting happens accidentally, such as incidentally to coughing or sneezing; on other occasions, intentional farting occurs through the tensing and releasing of the anal sphincter.

Flatus is brought to the rectum in the same peristalsis method as feces, causing a similar feeling of urgency and discomfort. Nerve endings in the rectum learn to distinguish between flatus and feces, although loose stool can confuse these nerves, and sometimes results in accidental defecation.

Remedies

Dietary

Certain spices counteract the production of intestinal gas, most notably cumin, caraway and the closely related ajwain, turmeric, asafoetida (hing), epazote, and konbu kelp (a Japanese seaweed). Many people report that by reducing intake of most refined carbohydrates (such as rice, pasta, potatoes and bread), the amount of flatulence may decrease significantly. The water-soluble oligosaccharides in beans that contribute to production of intestinal gas can be reduced through a regime of brief boiling followed by a long period of soaking, but at a cost of also leaching out other water-soluble nutrients. Also, gas can be reduced by fermenting the beans, and making them less gas-inducing, by cooking them in the liquor from a previous batch. Lactobacillus casei and Lactobacillus plantarum have recently been proven responsible for this effect ^*. Some legumes also stand up to prolonged cooking, which can help break down the oligosaccharides into simple sugars. Fermentation also breaks down oligosaccharides, which is why fermented bean products such as miso and tofu are less likely to produce as much intestinal gas.

Probiotics (yogurt, kefir etc.) often reduce flatulence when they are used to restore balance to the normal intestinal flora. Prebiotics, which generally are non-digestible oligosaccharides, such as FOS, generally increase flatulence in a similar way as described for lactose intolerance.

Medicinal activated charcoal tablets have also been reported as effective in reducing both odor and quantity of flatus when taken immediately before food that is likely to cause flatulence later.

Pharmacological

Digestive enzyme supplements can significantly reduce the amount of flatulence that is caused by some components of foods not being digested by the body and feeding the microbes in the small and large intestines. It has been shown that alpha-galactosidase enzymes, which can digest complex sugars, are effective in reducing the volume and frequency of flatusGaniats TG, Norcross WA, Halverson AL, Burford PA, Palinkas LA. "Does Beano prevent gas? A double-blind crossover study of oral alpha-galactosidase to treat dietary oligosaccharide intolerance." J Fam Pract. 1994;39:441-445.. The enzymes alpha-galactosidase (brands Beano, Bean-zyme), lactase (brand Lactaid), amylase, lipase, protease, cellulase, glucoamylase, invertase, malt diastase, pectinase, and bromelain are available, either individually or in combination blends, in commercial products.

The antibiotic rifaximin, often used to treat diarrhea caused by the microorganism E. coli, has been shown to reduce both the production of intestinal gas and the frequency of flatus eventsDi Stefano M, Strocchi A, Malservisi S, Veneto G, Ferrieri A, Corazza GR. "Non-absorbable antibiotics for managing intestinal gas production and gas-related symptoms." Aliment Pharmacol Ther. 2000;14:1001-1008..

While not affecting the production of the gases themselves, surfactants (agents which lower surface tension) can reduce the disagreeable sensations associated with flatulence, by aiding the dissolution of the gases into liquid and solid fecal matter.

Often it is helpful to ingest small quantities of acidic liquids with meals, such as lemon juice or vinegar, to stimulate the production of hydrochloric acid, which in turn increases enzyme production. This facilitates digestion and may limit gas production.

Health effects

As a normal body function, the action of flatulence is an important signal of normal bowel activity and hence is often documented by nursing staff following surgical or other treatment of patients. However, symptoms of excessive flatulence can indicate the presence of irritable bowel syndrome or some other organic disease. In particular, the sudden occurrence of excessive flatulence together with the onset of new symptoms provide reason for seeking further medical examination.

There is no particular harm to come from holding in flatus. Flatulence is not poisonous; it is a natural component of various intestinal contents. However, discomfort may develop from the build-up of gas pressure. In theory, pathological distension of the bowel, leading to constipation, could result if a person holds in flatus.

Not all flatus is released from the body via the anus. When the partial pressure of any gas component of the intestinal lumen is higher than its partial pressure in the blood, that component enters into the bloodstream of the intestinal wall by the process of diffusion. As the blood passes through the lungs this gas can diffuse back out of the blood and be exhaled. If a person holds in flatus during daytime, it will often be released during sleep when the body is relaxed. Some flatus can become trapped within the feces during its compaction and will exit the body, still contained within the fecal matter, during the process of defecation.

Recording flatulence events

The term meteorism is defined as the presence of gas within the abdomen or intestines. However, it is sometimes also used to describe the condition of excessive flatulence. Since subjective judgements vary considerably about what constitutes normal and elevated levels of flatulence, medical personnel sometimes instruct a patient complaining about excessive flatulence to maintain a personal flatulence diary. Researchers studying flatulence have also developed what is called a flatulogram. Its horizontal axis represents time (typically 24 hours, with each hour being marked on the time line). The subject is instructed to make a pencil mark on this line at each point in time that they notice flatus passing through the anus. The acoustic volume of the event is indicated by the vertical distance that the pencil mark rises above the time line. Inaudible events are indicated by a short mark that extends only below the time line.

Environmental impact

Livestock are a significant contributing factor to the greenhouse effect, accounting for around 20% of global methane emissionsLess than 10% of the total greenhouse gas emissions from livestock is produced by animal flatulence; most is produced by animal burping. Livestock in New Zealand account for 60% of the country's greenhouse gas emissionsAustralia contribute approximately 14% of that country's greenhouse gas emissions [http://www.mycattle.com/health/dsp_health_article.cfm?storyid=4086" target="_blank" >^*.

Social context

The Neutral point of view of this article or section may be compromised by "Avoid weasel words".
Please see the relevant discussion on the Articles with weasel words

In many cultures, excessive human flatulence is regarded as embarrassing and impolite, even to the point of being a taboo subject; and hence a natural subject for toilet humour.

People will often strain to hold in the passing of gas when in polite company, or position themselves to conceal the noise and smell.

Flatulence is a potential source of humor, either due to the foul smell or the sounds produced. Some find humor in flatulence ignition, which is possible due to the presence of flammable gases such as hydrogen and methane, though the process can result in burn injuries to the rectum and anus.

The History of Farting by Benjamin Bart is a collection of assorted limericks, facts, and blurbs on farting, while Who Cut the Cheese: A Cultural History of the Fart by Jim Dawson gives a more complete cultural discussion of the historical and social significance of farting.

Literature and the arts

In Dante's Divine Comedy, the last line of Inferno Chapter XXI reads: ed elli avea del cul fatto trombetta ("and he used his buttocks as a trumpet"), in the last example the use of this natural body function underlined a demoniac condition.

In Chaucer's "Miller's Tale" (one of the Canterbury Tales), the character Nicholas hangs his buttocks out of a window and farts in the face of his rival Absolom. Absolom then sears Nicholas's bum with a red-hot poker ("Nicholas quickly raised the window and thrust his ass far out...At this Nicholas let fly a fart with a noise as great as a clap of thunder, so that Absolom was almost overcome by the force of it. But he was ready with his hot iron and smote Nicholas in the middle of his ass."). (Lines 690–707)

In James Joyce's Ulysses, the main character Leopold Bloom breaks wind in the "Sirens" chapter of the book. ^*

In Emile Zola's La Terre (the 15th volume of the series Les Rougon-Macquart), the eldest Fouan son can fart at will and keeps winning free drinks by betting on his skill.

In the translated version of Penguin's 1001 Arabian Nights Tales, a story titled "The Historic Fart" tells of a man that flees his country from the sheer embarrassment of farting at his wedding.

Montaigne, in his essay "Of the Force of Imagination", includes a discussion of flatulence. Of "the vessels that serve to discharge the belly", he writes "I myself knew one so rude and ungoverned, as for forty years together made his master vent with one continued and unintermitted outbursting, and 'tis like will do so till he die of it"^*.

In the cinema, flatulating has been featured in films intended for adult audiences such as Blazing Saddles, however this caused some controversy in the United States: when it was run as a movie of the week by ABC the farting sounds were overdubbed with sounds from the surrounding horses, so the scene had cowboys sitting around a campfire standing up and leaning over for no apparent reason (Dawson, 1999, p. 125).

The Gas We Pass is a popular children's book in the United States about flatulence.

An episode of MythBusters featured myths about flatulence and determined the chemical composition of a typical flatus.

"I fart in your general direction" is a popular phrase from Monty Python and the Holy Grail.

Curiosities

According to "The Great Fart Survey" ^*, 39% of those who participated like the smell of their own farts.

Le Petomane "the Fartiste" a famous French performer in the nineteenth century as well as many professional farters before him did flatulence impressions and held shows.

An apocryphal story about Edward de Vere, Earl of Oxford is that he flatulated while swearing loyalty to Queen Elizabeth I and consequently went into self-imposed exile for seven years. After his return, the Queen was reported to have reassured de Vere: "My Lord, I had quite forgotten the fart." (John Aubrey, Brief Lives)

Emperor Claudius passed a law legalizing flatulating at banquets out of concern for people's health. There was a widespread misconception that a person could be poisoned by retaining flatus.

In August 2005, New Scientist magazine reported that inventors Michael Zanakis and Philip Femano had been awarded a US patent () for a "toy gas-fired missile and launcher assembly". The abstract of the patent makes it clear that this is, in fact, a fart-powered rocket:
"A ... missile is composed of a soft head and a tail extending therefrom formed by a piston. The piston is telescoped into the barrel of a launcher having a closed end on which is mounted an electrically activated igniter, the air space between the end of the piston and the closed end of the barrel defining a combustion chamber. Joined to the barrel, and communicating with the chamber therein, is a gas intake tube having a normally closed inlet valve. To operate the assembly, the operator places the inlet tube with its valve open adjacent ^* his anal region, from which a colonic gas is discharged. The piston is then withdrawn to a degree producing a negative pressure to inhale the gas into the combustion chamber to intermix with the air therein to create a combustible mixture. The igniter is then activated to explode the mixture in the chamber and fire the missile into space."

British inventors have also patented fart-related ideas, such as "A fart collecting device," which includes a drawing of the invention deployed and ready for action, with helpful numbers to identify the various components. "It comprises a gas-tight collecting tube 10 for insertion into the rectum of the subject. The tube 10 is connected to a gas-tight collecting bag (not shown). The end of the tube inserted into the subject is apertured and covered with a gauze filter and a gas permeable bladder 28."

Mambo Graphics, an Australian surfwear label, features the iconic "Farting Dog" design ^* in its lineup. Here the flatulence is depicted as a musical note emanating from the dog's backside.

References

"Burp vaccine cuts greenhouse gas emissions" by Rachel Nowak, New Scientist website, 25 September 2004, retrieved December 3 2005.
"Farmers raise stink over New Zealand 'fart tax'" by David Fickling,Guardian Unlimited, September 5 2003, retrieved December 3 2005.

Nontechnical Resources

External links

Reflexes | Flatulence | Gastroenterology

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