What causes belching?
The ability to belch is almost universal. Belching, also known as burping, 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. Moreover, the act of belching may actually cause more air to be swallowed. "Burping" infants during bottle or breast feeding 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 is often the cause of mild abdominal discomfort. As a result, people belch whenever mild abdominal discomfort is felt-whatever the cause.
If the problem causing the discomfort is not excessive air, then belching does not provide relief. 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 discomfort.

What causes bloating?
In discussing bloating, it is important to distinguish between bloating and distention. Bloating is the subjective sensation (feeling) that the abdomen is larger than normal. Thus, bloating is a symptom akin to the symptom of discomfort. In contrast, distention is the objective determination (physical finding) that the abdomen is actually larger than normal. Distention can be determined by such observations as the inability to fit into clothes or looking down at the stomach and noting that it is clearly larger than normal. 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. Nevertheless, bloating should never be assumed to be the same as distention.

What causes flatulence?
Flatulence, also known as farting, is the act of passing intestinal gas from the anus. Gas in the gastrointestinal tract has only two sources. It is either swallowed air or it is produced by bacteria that normally inhabit the intestines, primarily the colon. Swallowed air is rarely the cause of excessive flatulence. The usual source is the production of excessive gas by intestinal bacteria. The bacteria produce the gas (hydrogen and/or methane) when they digest foods, primarily sugars and polysaccharides (e.g., starch, cellulose), that have not been digested during passage through the small intestine. Sugars that are commonly poorly digested (maldigested) and malabsorbed are lactose, sorbitol, and fructose. Lactose is the sugar in milk. The absence of the enzyme lactase in the lining of the intestines, which is a genetic trait, causes the maldigestion. Lactase is important because it breaks apart the lactose so that it can be absorbed. Sorbitol is a commonly used sweetener in low calorie foods. Fructose is a commonly used sweetener in all types of candies and drinks.
Starches are another common source of intestinal gas. Starches are polysaccharides that are produced by plants and are composed of long chains of sugars. Common sources of different types of starch include wheat, oats, potatoes, corn, and rice. Rice is the most easily digested starch and little undigested rice starch reaches the colon and the colonic bacteria. Accordingly, the consumption of rice produces little gas. In contrast, the starches in wheat, oats, potatoes, and, to a lesser extent, corn, all reach the colon and the bacteria in substantial amounts. These starches, therefore, result in the production of appreciable amounts of gas.
The starch in whole grains produces more gas than the starch in refined (purified) grains. Thus, more gas is formed after eating foods made with whole wheat flour than with refined wheat flour. This difference in gas production probably occurs because the fiber present in the whole grain flour slows the digestion of starch as it travels through the small intestine. Much of this fiber is removed during the processing of whole grains into refined flour. Finally, certain fruits and vegetables, for example, cabbage, also contain poorly digested starches that reach the colon and result in the formation of gas.

*Gaseousness
Most vegetables and fruits contain cellulose, another type of polysaccharide that is not digested at all as it passes through the small intestine. However, unlike sugars and other starches, cellulose is used only very slowly by colonic bacteria. Therefore, the production of gas after the consumption of fruits and vegetables usually is not great unless the fruits and vegetables also contain sugars or polysaccharides other than cellulose.
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. First, it can be absorbed across the lining of the intestine into the blood. The gas then travels in the blood and ultimately is excreted in the breath. Second, gas can be removed and used by certain types of bacteria within the intestine. In fact, most of the gas that is formed by bacteria in the intestines is removed by other bacteria in the intestines. (Thank goodness!)

Excessive production of gas: Excessive production of gas by bacteria is a common cause of intermittent abdominal bloating/distention. Bacteria can produce too much gas in three ways. First, the amount of gas that bacteria produce varies from individual to individual. In other words, some individuals may have bacteria that produce more gas, either because there are more of the bacteria or because their particular bacteria are better at producing gas. Second, there may be poor digestion and absorption of foods in the small intestine, allowing more undigested food to reach the bacteria in the colon. The more undigested food the bacteria have, the more gas they produce. Examples of diseases of that involve poor digestion and absorption include lactose intolerance, pancreatic insufficiency, and celiac disease. Third, bacterial overgrowth can occur in the small intestine. Under normal conditions, the bacteria that produce gas are limited to the colon. In some medical conditions, these bacteria spread into the small intestine. When this bacterial spread occurs, food reaches the bacteria before it can be fully digested and absorbed by the small intestine. Therefore, the bacteria in the small intestine have a lot of undigested food from which to form gas. This condition in which the gas-producing bacteria move into the small intestine is called bacterial overgrowth of the small intestine (bowel). Excessive production of gas by bacteria is usually accompanied by more flatulence. Increased flatulence may not always occur, however, since gas potentially can be eliminated in other ways-absorption into the body, utilization by other bacteria, or possibly, by elimination at night without the knowledge of the gas-passer.

Physical obstruction: 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.

How is excessive intestinal gas treated?
The treatment of excessive intestinal gas depends on the cause. If there is maldigestion of specific sugars-lactose, sorbitol, or fructose--the offending sugars can be eliminated from the diet. In the case of lactose in milk, an alternative treatment is available. Enzymes that are similar to intestinal lactase can be added to the milk in order to break down the lactose prior to its ingestion so that it can be absorbed normally. Some people find that yogurt, in which the lactose has been broken down partially by bacteria, produces less gas than milk. There also are certain types of vegetables and fruits that contain types of starches that are poorly digested by people but well digested by bacteria. These include beans, lentils, cabbage, brussel sprouts, onions, carrots, bananas, apricots, and prunes. Reducing the intake of these vegetables and fruits, as well as foods made from whole grains, should reduce gas and flatulence. However, the list of gas-producing foods is rather long, and it may be difficult to eliminate them all without severely restricting the diet.
When maldigestion is due to pancreatic insufficiency, then supplemental pancreatic enzymes can be ingested with meals to replace the missing enzymes. If maldigestion and/or malabsorption is caused by disease of the intestinal lining, the specific disease must be identified, most commonly through a small bowel biopsy. Then, treatment can be targeted for that condition. For example, if celiac disease is found on the biopsy, a gluten-free diet can be started.
An interesting form of treatment for excessive gas is alpha-D-galactosidase, an enzyme that is produced by a mold. This enzyme, commercially available as Beano, is consumed as either a liquid or tablet with meals. This enzyme is able to break down some of the difficult-to-digest polysaccharides in vegetables so that they may be absorbed. This prevents them from reaching the colonic bacteria and causing unnecessary production of gas . Beano has been shown to be effective in decreasing the incidence of intestinal gas.
Two other types of treatment have been promoted for the treatment of gas; simethicone and activated charcoal. It is unclear if simethicone has an effect on gas in the stomach. However, it has no effect on the formation of gas in the colon. Moreover, in the stomach, simethicone would be expected only to affect swallowed air, which, as previously mentioned, is an uncommon cause of excessive intestinal gas. Nevertheless, some individuals are convinced that simethicone helps them. Activated charcoal has been shown to reduce the formation of gas in the colon, though the way in which it does so is unknown.