We all know what belching or burping is, but what causes it? Some of the common causes for belching are:
- Swallowing large amounts of air
- Gulping food or drinking too rapidly
- Carbonated beverages...
We all know what belching or burping is, but what causes it? Some of the common causes for belching are:
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.
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.
It is important to distinguish between bloating and distention.
In some instances, bloating may represent a mild form of distention since the abdomen does not become physically (visibly or measurably) enlarged until its volume increases by one quart. Bloating and even mild cases of distention may be caused by relaxation of the muscles of the abdominal wall and downward movement of the diaphragm.
There are three ways in which abdominal distention can arise. The causes are an increase in air, fluid, or tissue within the abdomen. The diseases or conditions that cause an increase of air, fluid, or tissue are very different from one another. Therefore, it is important to determine what (air, fluid, tissue) is distending the abdomen.
There are two types of distention; continuous and intermittent.
Flatulence, also known as farting, is the act of passing intestinal gas from the anus. The average person farts less than 20 times per day. Gas in the gastrointestinal tract has only two sources. It is either swallowed air or is produced by bacteria that normally inhabit the intestines, primarily the colon. Swallowed air rarely is the cause of excessive flatulence.
The source of excessive gas is intestinal bacteria. The bacteria produce the gas (primarily hydrogen and/or methane) when they digest foods, primarily sugars and nondigestible polysaccharides (for example, starch, cellulose), that have not been digested during passage through the small intestine. The bacteria also produce carbon dioxide, but the carbon dioxide is so rapidly absorbed from the intestine that very little passes in flatus.
Sugars that are commonly digested poorly (maldigested) and malabsorbed are lactose, sorbitol, and fructose.
Starches are another common source of intestinal gas. Starches are polysaccharides that are produced by plants and are composed of long chains of sugars, primarily fructose. Common sources of different types of starch include wheat, oats, potatoes, corn, and rice.
Small amounts of air are continuously being swallowed and bacteria are constantly producing gas. Contractions of the intestinal muscles normally propel the gas through the intestines and cause the gas to be expelled. Flatulence (passing intestinal gas) prevents gas from accumulating in the intestines.
However, there are two other ways in which gas can escape the intestine besides flatulence.
Foods that cause gas fall into a category summarized by the acronym, FODMAP, which stands for "fermentable oligosaccharides, disaccharides, monosaccharides, and polyols." Many people attempt a FODMAP elimination diet, but it can be difficult to eliminate these dietary constituents because they are present in a majority of foods. Any condition causing flatulence will respond to a low FODMAP diet, but the diet is not an easy one to follow, and may require the assistance of a dietician. If the diet is successful it may be possible to add back some of the excluded foods without a recurrence of flatulence. Examples of FODMAP foods include:
With such an extensive list of foods to be avoided, it is no surprise that a low FODMAP diet is difficult to initiate and maintain. That is why it is most important to look for a medical condition that is responsible for the excessive gas.
Excessive production of gas by bacteria is a common cause of intermittent abdominal bloating/distention. Theoretically bacteria can produce too much gas in three ways.
Excessive production of gas by bacteria usually is accompanied by flatulence. Increased flatulence may not always occur; however, since gas can be eliminated in other ways such as absorption into the body, utilization by other bacteria, or possibly, by elimination at night without the awareness of the gas-passer.
An obstruction (blockage) can occur virtually anywhere from the stomach to the rectum. When the blockage is temporary or partial, it can cause intermittent abdominal bloating/distention. For example, scarring of the pylorus (pyloric stenosis) can obstruct the opening from the stomach into the intestines, thereby blocking the complete emptying of the stomach. After meals, the stomach is normally filled with food and swallowed air. Then, during the next hour or two, the stomach secretes acid and fluid, which mix with the food and assist in digestion. As a result, the stomach distends further. When the obstruction is incomplete, the food, air, and fluid eventually pass into the intestines and the bloating/distention resolves.
An obstruction in the small bowel, which is most commonly due to adhesions (scarring that kinks the intestines) from a previous surgery, is another cause of intermittent abdominal distention. To make matters worse, the distention that is caused by the physical obstruction stimulates both the stomach and intestines to secrete fluid, which adds to the distention.
Severe constipation or fecal impaction (hardened stool in the rectum) also can obstruct the flow of the intestinal contents and result in distention. In this case, however, the bloating or distention usually is constant and progressive and is relieved by bowel movements or removal of the impacted stool.
A functional obstruction is not caused by an actual physical blockage, but rather by the poor functioning of the muscles of the stomach or intestines that propel the intestinal contents. When these muscles are not working normally, the intestinal contents will accumulate and distend the abdomen. Examples of functional obstruction include:
There is accumulating evidence that some patients with abdominal bloating and distention due to gas may have a functional abnormality of the intestinal muscles that prevents gas from being normally transported through the intestine and expelled. Instead, their gas accumulates in the intestine. Among patients with irritable bowel syndrome (IBS) with abdominal bloating or distention as an important symptom, the gas accumulates in the small intestine and not the colon. The gas accumulates during the day and is greatest in the evening.
Fats in food have an effect on the intestine that mimics a functional obstruction. Dietary fat reaching the small intestine causes transport of digesting food, gas, and liquid within the intestines to slow. This can promote the accumulation of food, gas, and liquid and lead to bloating and/or distention.
Dietary fiber or fiber used for treating constipation can cause bloating without increasing the production of gas in the intestine. It is believed that this sensation of bloating (and possibly even distention) is caused by the slowed passage of gas through the intestine which is caused by fiber. Of course, some types of fiber may lead to increased production of gas because they are digested to some extent by the colonic bacteria.
Some people appear to be very sensitive (hypersensitive) to distention of their intestines, and they may feel bloated even with normal amounts of digesting food, gas, and fluid in the intestine after a meal. The bloating may be aggravated or even progress to distention if the meal contains substantial amounts of fat, perhaps because fat slows the transit of gas and digesting food out of the stomach and small intestine.
Excessive gas, belching, bloating, and flatulence are usually treated by a gastroenterologist. Often a dietician can be of great help in dealing with specialized diets and identifying foods that can be most at fault.
A patient's medical history is important because it directs the evaluation.
Simple X-rays of the abdomen, particularly if they are taken during an episode of bloating or distention, often can confirm air as the cause of the distention since large amounts of air can be seen easily within the stomach and intestine. Moreover, the cause of the problem may be suggested by noting where the gas has accumulated. For example, if the air is in the stomach, emptying of the stomach is likely to be the problem.
X-rays of the small intestine, in which barium is used to fill and outline the small intestine, are particularly useful for determining if there is an obstruction of the small intestine.
These studies measure the ability of the stomach to empty its contents. For gastric emptying studies, a test meal that is labeled with a radioactive substance is eaten and a Geiger counter-like device is placed over the abdomen to measure how rapidly the test meal empties from the stomach. A delay in emptying of the radioactivity from the stomach can be caused by any condition that reduces emptying of the stomach (for example, pyloric stenosis, gastroparesis).
Imaging studies, including ultrasound examination, computerized tomography (CT), and magnetic resonance imaging (MRI), are particularly useful in defining the cause of distention that is due to enlargement of the abdominal organs, abdominal fluid, and tumor.
Two types of tests are used to diagnose maldigestion and malabsorption; general tests and specific tests.
The best general test is a 72 hour collection of stool in which the fat is measured; if maldigestion and/or malabsorption exist because of pancreatic insufficiency or diseases of the lining of the small intestine (for example, celiac disease), the amount of fat in the stool will increase before proteins and starches.
Specific tests can be done for maldigestion of individual sugars that are commonly maldigested, including lactose (the sugar in milk) and sorbitol (a sweetener in low calorie foods). The specific tests require ingestion of the sugars followed by hydrogen/methane breath testing. (See below.) The sugar fructose, a commonly used sweetener, like lactose and sorbitol, also may cause abdominal bloating/distention and flatulence. However, the problem that can occur with fructose is different from that with lactose or sorbitol. Thus, as already described, lactose and sorbitol may be poorly digested by the pancreatic enzymes and small intestine. Fructose, on the other hand, may be digested normally but may pass so rapidly through the small intestine that there is not enough time for digestion and absorption to take place.
The most convenient way to test for bacterial overgrowth of the small intestine is hydrogen/methane breath testing. Normally, the gas produced by the bacteria of the colon is composed of hydrogen and/or methane. For hydrogen/methane breath testing, a non-digestible sugar, lactulose, is consumed. At regular intervals following ingestion, samples of breath are taken for analysis. When the lactulose reaches the colon, the bacteria form hydrogen and/or methane. Some of the hydrogen or methane is absorbed into the blood and eliminated in the breath where it can be measured in the samples of breath.
In normal individuals, there is one peak of hydrogen or methane when the lactulose enters the colon. In individuals who have bacterial overgrowth, there are two peaks of hydrogen or methane. The first occurs when the lactulose passes and is exposed to the bacteria in the small intestine. The second occurs when the lactulose enters the colon and is exposed to the colonic bacteria. Hydrogen breath testing for overgrowth also may be done utilizing lactose, glucose, sorbitol, or fructose as the test sugar.
The treatment of excessive intestinal gas depends on the cause.
A recent study has shed additional light on the role of intestinal gas and the way in which it causes symptoms. Investigators studied 30 patients whose primary complaint was flatulence (although they also had other complaints such as abdominal bloating, distension and/or discomfort), and 20 healthy people (controls) without issues related to gas. The investigators studied the patients' and controls' production of gas and symptoms on their normal (basal) diet, during and following a standard meal, and during and following a meal that contained foods known to cause more gas (flatulent diet). During the basal period on their usual diet, not surprisingly, the patients had more symptoms than the controls and evacuated gas (farted) more often than controls (22 vs. 7 times during the day). Interestingly, however, the patients and controls produced the same total volume of gas while on the standard meal. This would suggest that the patients were NOT producing more gas than the controls. Two explanations for these observations would be 1) that the basal diet contained more gas-producing foods, or 2) that patients were more sensitive to gas, i.e., they developed more discomfort producing the same amount of gas as controls (farting more frequently, but with less gas per fart).
On the flatulogenic diet, the controls developed some symptoms, but the patients, not surprisingly, developed worse symptoms. The number of farts increased for both patients and controls but more so for the patients, (44 vs. 22 farts, respectively). Nevertheless, the total amount of gas that was produced on the flatulogenic diet was the same for controls and patients. This supported the probability that patients were more sensitive to gas, i.e., they developed more symptoms, and farted more even though they were producing the same amount of gas as controls.
The observations made in this study add considerably to our understanding of intestinal gas and the mechanism whereby gas causes symptoms. In the group of patients that was studied, the symptoms were caused by an abnormal sensitivity to gas and not to the production of more gas. It is important to recognize, however, that although this may be the mechanism for production of symptoms in this group of patients, there are undoubtedly other explanations or contributing factors in other patients with symptoms and flatulence. For example and as explained previously, some patients may retain more gas in the abdomen due to problems with the intestinal muscles leading to intestinal distention and discomfort. Some patients may be on a flatulogenic diet without realizing it, and some patients may indeed be producing more gas than others on the same diet.
Agrawal, A., et al. "Review Article: Abdominal Bloating and Distension in Functional Gastrointestinal Disorders -- Epidemiology and Exploration of Possible Mechanisms." Aliment Pharmacol Ther. 2008;27(1):2-10.
Azpiroz, et al. "Abdominal Bloating." Gastroenterology; September 2005 Vol. 129, Issue 3, p1060–1078.
Houghton , L. et al. "Relationship of Abdominal Bloating to Distention in Irritable Bowel Syndrome and Effect of Bowel Habit." Gastroenterology; July 2005. Vol. 131, Issue 4, p1003–1010.
Manichanh, C. et al. "Anal gas evacuation and colonic microbiota in patients with flatulence: effect of diet." Gut 2014;63:401-408.
Salvioli , B. et al. "Origin of gas retention and symptoms in patients with bloating." Gastroenterology; March 2005. Vol. 128, Issue 3, p574–579.
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