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What causes belching (burping)?
The ability to belch is almost universal. Belching, also
known as burping (medically referred to as eructation), is the act of expelling gas from the stomach out through the
mouth. The usual cause of belching is a distended (inflated) stomach caused by
swallowed air. The distention of the stomach causes abdominal discomfort, and the
belching expels the air and relieves the discomfort. The common reasons for
swallowing large amounts of air (aerophagia) are gulping food or drink too
rapidly, anxiety, and carbonated beverages. People are often unaware that they
are swallowing air. "Burping" infants during bottle or
breastfeeding is important in order to expel air in
the stomach that has been swallowed with the formula or milk.
Excessive air in the stomach is not the only cause of belching. For some
people, belching becomes a habit and does not reflect the amount of air in their
stomachs. For others, belching is a response to any type of abdominal discomfort
and not just to discomfort due to increased gas. Everyone knows that when they
have mild abdominal discomfort, belching often relieves the problem. This is
because excessive air in the stomach often is the cause of mild abdominal
discomfort. As a result, people belch whenever mild abdominal discomfort is felt
regardless of its cause.
Belching is not the simple act that many people think it is. Belching requires the coordination of several activities.
The larynx must be closed-off so that any liquid or food that might return with the air from the stomach won't get into the lungs.
This is accomplished by voluntarily raising the larynx as is done when swallowing.
Raising the larynx also relaxes the upper esophageal sphincter so that air can pass more easily from the esophagus into the throat.
The lower esophageal sphincter must open so that air can pass from the stomach into the esophagus.
While all this is occurring, the
diaphragm descends just as it does when a breath is taken.
This increases abdominal pressure and decreases pressure in the chest.
The changes in pressure promote the flow of air from the stomach in the abdomen to the esophagus in the chest.
One unusual type of belching has been described in individuals who
habitually belch. It has been demonstrated that during their belches,
air in the room enters the esophagus and is immediately expelled
without even entering the stomach, giving rise to a belch. This in and out flow of air also is likely to be the explanation for the ability of many people to belch at will, even when there is little or no air in the stomach.
Such belching is referred to as esophageal belching.
If the problem causing the discomfort is not excessive air in the stomach, then belching
does not provide relief from the discomfort. When belching does not ease the discomfort, the
belching should be taken as a sign that something may be wrong within the abdomen,
and the cause of the discomfort should be sought. Belching by itself, however,
does not help the physician determine what may be wrong because belching can
occur in virtually any abdominal disease or condition that causes abdominal discomfort.