Flatulence is the expulsion through the
rectum of a mixture of gases that are byproducts of
the digestion process of
mammals and other
animals. The mixture of gases is known as
flatus,
(informally)
fart, or simply
gas,
and is expelled from the
rectum in a process
colloquially referred to as "passing gas" or "
farting". Flatus is brought to the rectum by the same
peristaltic process which causes feces
to descend from the large intestine. The
noises commonly associated with flatulence are caused
by the
vibration of the
anal sphincter, and
occasionally by the closed
buttocks.
Composition of flatus gases
Nitrogen, the main constituent of
air, is the primary
gas released
during flatulence, along with
carbon
dioxide, which is present in higher quantities in those who
drink
carbonated beverages
regularly. The lesser component gases
methane and
hydrogen are
flammable, and so flatus containing
adequate amounts of these can be
ignited. However, 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
archaea capable of producing
methane. Similar results are found in samples of gas obtained from
within the
rectum.
The gas released during a flatus event frequently has an unpleasant
odor. For many years, this was thought to be due to
skatole and
indole, which are
byproducts of the
digestion of
meat. However,
gas
chromatography testing in 1984 revealed that
sulfur-containing compounds, such as
methanethiol,
hydrogen sulfide (rotten egg smell) and
dimethyl sulfide, were primarily
responsible for the scent.
The incidence of odoriferous compounds in flatulence emissions
increases from
herbivores, such as
cattle, through
omnivores to
carnivorous species, such
as
cats. Such odor can also be caused by the
presence of large numbers of microflora
bacteria and/or the presence of feces in the
rectum.
The major components of the flatus, which are odorless, by
percentage are:
Mechanism of action
Flatus is brought to the
rectum by the same
process which causes
feces to descend from the
large intestine, and may cause a similar feeling of urgency and
discomfort. Nerve endings in the rectum usually enable individuals
to distinguish between flatus and feces,
although loose stool can confuse the individual, occasionally
resulting in accidental defecation.
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 water and body fat. The auditory pitch (sound) of
the flatulence outburst can also be affected by the anal
embouchure. Among humans, flatulence occasionally
happens accidentally, such as incidentally to
coughing or
sneezing or during
orgasm; on other occasions, flatulence can be
voluntarily elicited by tensing the
rectum or
"bearing down" on stomach or bowel muscles and subsequently
relaxing the anal sphincter, resulting in the expulsion of a
flatus.
Causes
Intestinal gas is composed of varying quantities of exogenous
sources (air that is ingested through the nose and mouth) and
endogenous sources (gas produced within the digestive tract). The
exogenous gases are swallowed (
aerophagia) when eating or drinking or increased
swallowing during times of excessive salivation (as might occur
when nauseated or as the result of
gastroesophageal reflux disease).
The
endogenous gases are produced either
as a by-product of digesting certain types of
food, or of incomplete
digestion. Anything that causes food to be
incompletely digested by the
stomach and/or
small intestine may cause flatulence
when the material arrives in the large intestine, due to
fermentation by
yeast or
prokaryotes
normally or abnormally present in the
gastrointestinal tract.
Flatulence-producing foods are typically high in certain
polysaccharides, (especially
oligosaccharides such as
inulin). Those foods include
beans,
lentils,
dairy products,
onions,
garlic,
scallions,
leeks,
turnips,
rutabagas,
radishes,
sweet potatoes,
potatoes,
cashews,
Jerusalem artichokes,
oats,
wheat, and
yeast in
breads.
Cauliflower,
broccoli,
cabbage,
Brussels sprouts and other
cruciferous vegetables that belong to
the
genus Brassica are
commonly reputed to not only increase flatulence, but to increase
the pungency of the flatus. In beans, endogenous gases seem to
arise from complex
oligosaccharide
(
carbohydrates) that are particularly
resistant to digestion by mammals, but which are readily digestible
by
microorganisms (methane-producing
archaea;
Methanobrevibacter smithii)
that inhabit the
digestive tract.
These
oligosaccharides pass through
the upper
intestine largely unchanged, and
when they reach the lower
intestine,
bacteria feed on them, producing copious
amounts of flatus. In the case of people who have
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. In the field of mountaineering,
high altitude flatus
expulsion was first noticed over two hundred years ago.
Remedies
Dietary
Certain
spices have been reported to
counteract the production of intestinal gas, most notably
cumin,
coriander,
caraway and the closely related
ajwain,
turmeric,
asafoetida (Hing),
epazote, and
kombu kelp (a Japanese
seaweed). Most
starches, including potatoes, corn, noodles, and wheat, produce gas
as they are broken down in the large intestine. Rice is the only
starch that does not cause gas. The amount of water-soluble
oligosaccharide in beans that may
contribute to production of intestinal gas is reputed to be reduced
by a long period of soaking followed by boiling, but at a cost of
also leaching out other water-soluble nutrients. Also, intestinal
gas can be reduced by fermenting the beans, and making them less
gas-inducing, and/or by cooking them in the liquor from a previous
batch.
Lactobacillus casei and
Lactobacillus
plantarum have recently been hypothesized as being
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 are less likely to produce as much
intestinal gas).
Probiotics (
live
yogurt,
kefir, etc.) are reputed to reduce
flatulence when used to restore balance to the normal
intestinal flora. Live yogurt contains
Lactobacillus
acidophilus which may be useful in reducing flatulence.
L. acidophilus
may make the intestines more acidic, thus maintaining the natural
balance of fermentation processes.
L. acidophilus is available
in supplements (some believe non-dairy is best).
Prebiotics, which generally are non-digestible
oligosaccharides, such as
fructooligosaccharide, generally
increase flatulence in a similar way as described for lactose
intolerance.
Medicinal
activated charcoal
tablets (brand name CharcoCaps) 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 may
significantly reduce the amount of flatulence caused by some
components of foods not being digested by the body and thereby
promoting the action of microbes in the small and large
intestines. It has been suggested that
alpha-galactosidase enzymes, which can digest certain complex sugars,
are effective in reducing the volume and frequency of flatus. The
enzymes alpha-galactosidase ),
lactase,
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, may reduce both the production of intestinal gas and
the frequency of flatus events.
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.
Preparations containing simethicone reportedly operate by promoting the coalescence of smaller bubbles into larger ones more easily passed from the body, either by burping or flatulence. Such preparations do not decrease the total amount of gas generated in or passed from the colon, but make the bubbles larger and thereby allowing them to be passed more easily.
Often it may be helpful to ingest small quantities of
acidic liquids with meals, such as
lemon juice or
vinegar,
to stimulate the production of
gastric
hydrochloric acid. In turn, acid
ingestion may increase normal
gastric
enzyme and acid production, facilitating normal
digestion and perhaps limiting intestinal gas
production. Ingestion of
bromelain- or
papain-containing supplements (such as raw
pineapple or
papaya,
respectively,) may be helpful.
Odor from flatulence, caused by the intestinal
bacteria called microflora in the bowel, can be treated by taking
bismuth subgallate, available
over-the-counter as Devrom.
Bismuth
subgallate is commonly used by individuals who have had
ostomy surgery,
bariatric surgery,
fecal incontinence and
irritable bowel syndrome.
Post-release
In 1998,
Chester "Buck" Weimer of Pueblo, Colorado
received a patent for the first undergarment that contained a replaceable
charcoal filter. The
undergarments are
air-tight and
provide a pocketed
escape
hole in which a charcoal filter can be inserted.
A similar product was released in 2002, but rather than an entire
undergarment, consumers are able to purchase an insert similar to a
pantiliner that contains activated
charcoal.
The inventors, Myra and Brian Conant of
Mililani,
Hawaii
still claim on their website to have discovered the
undergarment product in 2002 (eight years after Chester Weimer
filed for a patent for his product), but state that their tests
"concluded" that they should release an insert
instead.
Health effects
As a normal body function, the action of flatulence is an important
signal of
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.
Flatulence is not
poisonous; it is a
natural component of various intestinal contents. However,
discomfort may develop from the build-up of gas pressure if an
attempt is made to refrain from releasing them. In theory,
pathological distension of the bowel, leading to
constipation, could result if a person holds in
flatulence.
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
involuntarily 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.
Environmental impact
Flatulence is often blamed as a significant source of
greenhouse gases, owing to the erroneous
belief that the methane released by
livestock is in the flatus. While livestock
account for around 20% of global
methane
emissions, 90-95% of that is released by
exhaling or
burping. Only 1–2%
of global methane emissions come from livestock flatus.
Since
New
Zealand
produces large amounts of agricultural product it
is in a unique position of having high methane emissions livestock
compared to other greenhouse gas sources. The New Zealand
government is a signatory to the
Kyoto
Protocol and therefore, attempts are being made to reduce
greenhouse emissions. To achieve this an
agricultural emissions
research levy was proposed, which promptly became known as a
"fart tax" or "flatulence tax". It encountered opposition from
farmers, farming lobby groups and opposition politicians.
In
Fresno,
California
, a system to harvest methane by-product from dairy
cattle and convert it to usable bio-gas is being used, in a
partnership with Pacific Gas
& Electric (PG&E) and BioEnergy Solutions, in which
BioEnergy Solutions sells the methane harvested from cows to
PG&E, who then converts the methane to usable bio-gas, which is
very similar to natural gas.
In June 2009
Paul McCartney and other
celebrities launched a "Meat Free Monday" campaign in order to
reduce greenhouse gas emissions from the world's livestock.
Social context
In many
cultures, human flatulence in public
is regarded as embarrassing but, depending on context, can also be
considered humorous . People will often strain to hold in the
passing of gas when in polite company, or position themselves to
conceal the noise and scent. In other cultures, it may be no more
embarrassing than
coughing.
While the act of passing flatus in said cultures is generally
considered to be an unfortunate occurrence in public settings,
flatulence may, in casual circumstances and especially among
children, be used as either a humorous supplement to a joke
("
pull my finger"), or as a comic
activity in and of itself. The social acceptability of
flatulence-based humor in entertainment and the mass media varies
over the course of time and between cultures.
In 2008, a farting application for the
iPhone
raked in nearly $10,000 in one day.
Farting at will
Historical comment on the ability to fart at will is observed in
St. Augustine's
The City of God. Augustine, not
otherwise noted for his
levity, mentions men
who "have such command of their bowels, that they can break wind
continuously at will, so as to produce the effect of singing." The
fact that mankind in general has lost this ability he attributes to
the first sin of
Adam and Eve and its
consequences with respect to body control.
Le Pétomane ("The Fartiste") was a
famous French performer in the 19th century, as well as many
professional farters before him,
did flatulence impressions and held shows. The performer
Mr. Methane carries on Le Pétomane's tradition
today.
See also
References
Bibliography
- Allen, V. (2007) On Farting: Language and Laughter in the
Middle Ages. Palgrave MacMillan. ISBN 978-0-312-23493-5.
- Persels J. & Ganim, R. (2004) Fecal Matters in Early
Modern Literature and Art: Studies in Scatology. (Chap. 1: The
Honorable Art of Farting in Continental Renaissance). ISBN
0754641163
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