Belching, also known as burping, ructus, or eructation, involves the release of gas from the digestive tract (mainly esophagus and stomach) through the mouth. It is usually accompanied with a typical sound and, at times, an odor.
Belching is typically caused by eating or drinking too fast, and thereby swallowing (aerophagia
) and subsequently expelling air
, in which the expelled gas is a mixture of nitrogen
. Burps can also be caused by drinking carbonated
drinks such as beer
, soft drinks
, or champagne
, in which case the expelled gas is carbon dioxide
from the drink itself. Common diabetes drugs metformin and Byetta can cause belching, especially at higher doses. This often resolves in a few weeks. Belching combined with other symptoms such as dyspepsia
may be a sign of an ulcer
or hiatal hernia
, and should be reviewed by a physician.
The sound of burping is caused by the vibration of the upper esophageal sphincter as the gas passes through it. The current Guinness world record for the loudest burp is 118.1 dB, set by Paul Hunn from London, England in 2000. (This would be noticeably louder than a chainsaw at a distance of 1 meter.)
Social context and etiquette
In many parts of the world, audible burping is not much appreciated and is therefore considered to be somewhat impolite (although generally not as much as flatulence
). However, in other areas it can be considered a sign of completion of a meal or a form of applause for the cook. Sometimes, children and teenagers engage in burping contests to determine who can produce the loudest burp, the longest burp, the most guttural burp, the burping of words, songs, or even the alphabet.
are particularly subject to accumulation of gas in the stomach while feeding, and this can cause considerable agitation to the child unless it is burped
. The act of burping an infant involves placing the child in a position conducive to gas expulsion (for example holding the infant up to the adult's shoulder, with the infant's stomach resting on the adult's chest) and then lightly patting it on the lower back so that he or she burps.
Because burping can cause vomiting in infants, the burp cloth or burp pad is sometimes employed on the shoulder to protect the adult's clothing.
Many other mammals
, such as cattle
, and sheep
also burp. In the case of ruminants
, the gas expelled is actually methane
produced as a byproduct of the animal's digestive process
. Anaerobic organisms
such as Escherichia coli
) and methanogenic archaea
produce this effect. An average cow is thought to emit between 542 litres
(if located in a barn) and 600 litres (if in a field) of methane per day through burping and exhalation, making commercially farmed cattle a major contributor to the greenhouse effect
. 95% of this gas is emitted through belching. This has led scientists at the Commonwealth Scientific and Industrial Research Organisation
, to develop an anti-methanogen vaccine to minimize methane in cattle burps.
Some fish are also known to expel air from their gills; here the burp is produced by gas being expelled from the gas bladder.