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Flatulence is a mixture of gases that are produced by symbiotic bacteria and yeasts living in the gastrointestinal tract of mammals, and aerosolized particles of feces, and it is released under pressure through the anus with a characteristic sound and odor. Flatulence is known colloquially as farting, but some people find the word fart offensive and will use a euphemism as an alternative. Most animals, birds, fishes and insects also fart.

Amount and constituents

The average human releases 0.5 to 1.5 litres (1 to 3 U.S. pints) of flatus in 12 to 25 episodes throughout the day.

The primary constituents of flatulence (collectively known as flatus) are the non-odorous gases nitrogen (ingested), oxygen (ingested), methane (produced by anaerobic microbes), carbon dioxide (produced by aerobic microbes or ingested), and hydrogen (produced by some microbes and consumed by others). Odors result from trace amounts of other constituents (often sulfuric, see below).

Nitrogen is the primary gas released. While methane is popularly associated with flatulence, evidence suggests that two-thirds of all humans do not release methane at all in their flatulence. Methane is mostly caused by bacteria within the anal opening. Methane and hydrogen are flammable and as such some flatulence is susceptible to catching fire. Gas released mostly has a foul odor which mainly results from butyric acid (rancid butter smell) and sulfur compounds such as hydrogen sulfide (rotten egg smell) and carbon disulfide that are the result of protein breakdown.

Aerosolized particles of feces are also present in flatus, though in miniscule amounts.

Causes

Intestinal gas comes from exogenous (90%) and endogenous (10%) sources. Exogenous gas is air that is ingested through the nose and mouth. Endogenous gas is produced within the digestive tract.

The endogenous gases are produced as a by-product of digesting certain types of food. Flatulence producing foods are typically high in complex carbohydrates especially oligosaccharides such as inulin and include beans, milk, onions, yams, sweet potatoes, citrus rinds, chestnuts, broccoli, cabbage, Jerusalem artichokes, 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 gas (McGee 1984 pp.257-8).

In the case of those with lactose intolerance (i.e., most non-Caucasian humans), 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 not by a flapping of the posterior, as commonly thought, but by the vibration of the anal opening. 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.

Flatus is brought to the anus 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.

Remedies

Dietary

Certain spices counteract the production of intestinal gas, most notably cumin, caraway and the closely related ajwain, turmeric, asafoetida (hing) and konbu (a Japanese culinary seaweed closely related to kelp).

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.

Probiotics (yogurt, kefir, acidophilus, bifidus, etc.) and prebiotics (such as FOS) may also reduce flatulence if they are used to restore balance to the normal intestinal flora; used in excess, however, they may create an imbalance which increases flatulence.

Mechanical

In social situations where the sound of flatulence would be particularly inappropriate a temporary remedy can be obtained by placing a piece of cotton wool or paper tissue about 4 cm in diameter onto the anus. If this is done whilst squatting then closure of the buttocks will hold it in place for a considerable period of time. This keeps the anus dry and reduces the velocity of the gas discharge, both of which help to prevent noisy events.

For acute situations, it is recommended to spread the buttocks, so as to stretch open the sphincter while the gas is passed. This is best accomplished by sitting on one buttock, shifting body weight laterally, then putting the body weight on the other buttock. The opening will not snap shut and the passage will be silent. If done incorrectly, however, this may result in a characteristic high-pitched squeal.

If sitting on a cushioned surface, the gases can be directed into the open-cell polyurethane foam and somewhat quarantined. Following the fart, standing will not release the odor, in fact, the gases will be further pushed to the center of the cushion. The gases will leak out and not be detectable, unless the cushion is compressed again under the weight of another person.

Pharmacological

Digestive enzyme supplements can significantly reduce the amount of flatulence when that flatulence is caused by some components of foods not being digested by the body and feeding the microbes in the small and large intestines. The enzymes alpha-galactosidase (brands Beano, Bean-zyme), lactase (brand Lactaid), amylase, lipase, protease, cellulase, glucomylase, invertase, malt diastase, pectinase, and bromelain are available, either individually or in combination blends, in commercial products.

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

Cosmetic

Activated charcoal underwear and pads can be somewhat effective at reducing the odors of flatulence, but these products do not muffle the sound. Additional security can be obtained with common deodorizers and perfumes. Care should be taken to select a perfume that combats the odor, with floral and citrus notes, instead of musk, which would complement the offending odor.

Health effects

Breastfeeding mothers are advised to avoid gas producing food in their diet because breastfed babies can vomit when there is too much gas in their stomach.

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.

There is no particular harm to come from holding in farts. Farts are not poisonous, they are a natural component of intestinal contents. However, discomfort may develop from the buildup of gas pressure. In theory, pathological distention of the bowel could result if a person holds in farts.

Environmental impact

It is sometimes perceived that bovine flatulence is a source of greenhouse gas and may contribute to the greenhouse effect, however only one sixth of the total greenhouse gas emissions from livestock is produced by animal flatulence; the remainder is produced by animal burping. Livestock in New Zealand are said to produce about half of New Zealand's greenhouse gas emissions. Livestock in Australia contribute approximately 14 percent of that country's greenhouse gas emissions.

Social context

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 a fart when in polite company, or position themselves to conceal the noise and smell of a fart.

Flatulence can be considered humorous to some people, either due to the scent or the sounds produced. Some find humor in lighting farts, which works well due to the methane content.

Not all cultures consider flatulence an embarassing or amusing subject. People from the Punjab find it no more amusing or embarassing than sneezing.

Literature and the arts

The flatulence had a role in literature since the mists of time, as In Rabelais' Gargantua's cycle reads several times the word pet (fart).

In Dante's Divine Comedy, the last line of Inferno Chapter XXI reads: ed elli avea del cul fatto trombetta ("and he used his ass 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 arse out a window and farts in the face of his rival Absolom. Absolom then sears Nicholas's bum with a red-hot poker. (Lines 690 - 707)

A few individuals, such as Le Pétomane, have brought flatulence onto the stage in one-man shows.

In the cinema, farting is featured in Blazing Saddles, Kangaroo Jack, Fart: The Movie, American Pie, and Austin Powers, among others.

Farting is no longer summarily censored from television broadcasts. During the telecast of Super Bowl XXXVIII in the United States, a beer advertisement featured a horse passing gas.

Curiosities

Edward de Vere, Earl of Oxford farted 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 farting at banquets out of concern for peoples' health. There was a widespread misconception that a person could be poisoned by retaining farts.

See also

• professional farter

References

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External links

• The Merck Manual of Diagnosis and Therapy, Gas
• Facts on Farts
• Dictionary of Fart Slang
• Farting Cartoon

• Reflexes
• Flatulence
• Gastroenterology