Intestinal Gas (Belching, Bloating, Flatulence) (cont.)
What causes 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 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. Bloating and even very mild cases of distention may be
caused by relaxation of the muscles of the abdominal wall.
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 any of these three factors are very
different from one anther. Therefore, it is important to determine which of them
is distending the abdomen.
There are two types of distention; continuous and intermittent.
- Continuous
distention may be caused by the enlargement of an intra-abdominal (within the
abdomen) organ, an intra-abdominal tumor, a collection of fluid around the
intra-abdominal organs (ascites), or just plain
obesity.
- Intermittent distention
is usually due to the occasional accumulation of gas and/or fluid within the
stomach, small intestine, or colon.
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 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 (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
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
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.
- 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, some of the starches in wheat,
oats, potatoes, and, to a lesser extent, corn, all may reach the colon. These starches, therefore,
may 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 of the fiber
(similar to a complex starch) present in the whole grain flour. 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.
- 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!)
Next: What are the causes of intermittent abdominal bloating/distention? »
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