Everyone has gas and eliminates it by burping or passing it
through the rectum. However, many people think they have too much gas
when they really have normal amounts. Most people produce about 1 to 3
pints a day and pass gas about 14 times a day.
The most common symptoms of gas are belching, flatulence, abdominal
bloating, and abdominal pain. However, not everyone experiences these
symptoms. The determining factors probably are how much gas the body
produces, how many fatty acids the body absorbs, and a person's
sensitivity to gas in the large intestine. Chronic symptoms caused by
too much gas or by a serious disease are rare.
Gas is made primarily of odorless vapors-carbon dioxide, oxygen,
nitrogen, hydrogen, and sometimes methane. The unpleasant odor of
flatulence comes from bacteria in the large intestine that release
small amounts of gases that contain sulfur.
Although having gas is common, it can be uncomfortable and
embarrassing. Understanding causes, ways to reduce symptoms, and
treatment will help most people find relief.
Air swallowing (aerophagia) is a common cause of gas in the stomach.
Everyone swallows small amounts of air when eating and drinking.
However, eating or drinking rapidly, chewing gum, smoking, or wearing
loose dentures can cause some people to take in more air.
Burping, or belching, is the way most swallowed air--which contains
nitrogen, oxygen, and carbon dioxide--leaves the stomach. The remaining
gas moves into the small intestine where it is partially absorbed. A
small amount travels into the large intestine for release through the
rectum. (The stomach also releases carbon dioxide when stomach acid and
bicarbonate mix, but most of this gas is absorbed into the bloodstream
and does not enter the large intestine).
The body does not digest and absorb some carbohydrates (the sugar,
starches, and fiber found in many foods) in the small intestine because
of a shortage or absence of certain enzymes.
This undigested food then passes from the small intestine into the
large intestine, where harmless and normal bacteria break down the
food, producing hydrogen, carbon dioxide, and, in about one-third of
all people, methane. Eventually these gases exit through the rectum.
People who make methane do not necessarily pass more gas or have
unique symptoms. A person who produces methane will have stools that
consistently float in water. Research has not shown why some people
produce methane and others do not.
Foods that produce gas in one person may not cause gas in another.
Some common bacteria in the large intestine can destroy the hydrogen
that other bacteria produce. The balance of the two types of bacteria
may explain why some people have more gas than others.
Most foods that contain carbohydrates can cause gas. By contrast, fats and proteins cause little gas.
Sugars
The sugars that cause gas are: raffinose, lactose, fructose, and sorbitol.
Raffinose:
Beans contain large amounts of this complex sugar. Smaller amounts are
found in cabbage, brussels sprouts, broccoli, asparagus, other
vegetables, and whole grains.
Lactose:
Lactose is the natural sugar in milk. It is also found in milk
products, such as cheese and ice cream, and processed foods, such as
bread, cereal, and salad dressing. Many people, particularly those of
African, Native American, or Asian background, have low levels of the
enzyme lactase needed to digest lactose. Also, as people age, their
enzyme levels decrease. As a result, over time people may experience
increasing amounts of gas after eating food containing lactose.
Fructose:
Fructose is naturally present in onions, artichokes, pears, and wheat.
It is also used as a sweetener in some soft drinks and fruit drinks.
Sorbitol:
Sorbitol is a sugar found naturally in fruits, including apples, pears,
peaches, and prunes. It is also used as an artificial sweetener in many
dietetic foods and sugarfree candies and gums.
Starches:
Most starches, including potatoes, corn, noodles, and wheat, produce
gas as they are broken down in the large intestine. Rice is the only
starch that does not cause gas.
Fiber:
Many foods contain soluble and insoluble fiber. Soluble fiber dissolves
easily in water and takes on a soft, gel-like texture in the
intestines. Found in oat bran, beans, peas, and most fruits, soluble
fiber is not broken down until it reaches the large intestine where
digestion causes gas.
Insoluble fiber, on the other hand, passes essentially unchanged
through the intestines and produces little gas. Wheat bran and some
vegetables contain this kind of fiber.
The most common ways to reduce the discomfort of gas are changing
diet, taking medicines, and reducing the amount of air swallowed.
Many nonprescription, over-the-counter medicines are available to
help reduce symptoms, including antacids with simethicone and activated
charcoal. Digestive enzymes, such as lactase supplements, actually help
digest carbohydrates and may allow people to eat foods that normally
cause gas.
Activated charcoal tablets (Charcocaps) may provide relief from gas
in the colon. Studies have shown that when taken before and after a
meal, intestinal gas is greatly reduced. Both the number of flatus
events and breath hydrogen levels were measured. These experiments
showed that orally administered activated charcoal was effective in
preventing the large increase in the number of flatus events and
increased breath hydrogen concentrations that normally occur following
a gas-producing meal. The usual dose is 2 to 4 tablets taken just
before eating and 1 hour after meals.
The enzyme lactase, which aids with lactose digestion, is available
in liquid and tablet form without a prescription (Lactaid, Lactrase,
and Dairy Ease). Adding a few drops of liquid lactase to milk before
drinking it or chewing lactase tablets just before eating helps digest
foods that contain lactose. Also, lactose-reduced milk and other
products are available at many grocery stores (Lactaid and Dairy Ease).
Beano, an over-the-counter, digestive aid, contains the an oral
solution of alpha-galactosidase (sugar-digesting enzyme) that the body
lacks to digest the sugar in beans and many vegetables. The enzyme
comes in liquid form. Three to 10 drops are added per serving just
before eating to break down the gas-producing sugars. Beano has no
effect on gas caused by lactose or fiber.
In another study it has been shown that proper cooking (especially
of beans and peas) can reduce the incidence and discomforts of
flatulece.
Abdominal discomfort after eating cowpeas is known to be a major
constraint on their greater consumption. Problems associated with
cowpea consumption were identified by questionnaire in 448 randomly
selected families. Some (28%) of the respondents had never experienced
flatulence. Those who did said it occurred when cowpeas were eaten at
all (16.7%), as dinner (42%) or without other foods (15%). A subsample
of 40 people who complained of serious abdominal discomfort were fed
cowpeas cooked by eight different methods at three consecutive dinners
for each method. The problems reported were indigestion, vomiting,
diarrhoea, increased belching, bad breath, offensive stool, flatulence,
constipation, mild abdominal discomfort and sleepiness. Many
respondents complained of mild abdominal discomfort with undehulled
cowpeas (72.5%) and dehulled cowpeas (42.5%) that had been cooked at
atmospheric pressure. Only 12.5% of the respondents complained of
discomfort with dehulled cowpeas cooked under extra pressure. Thus,
dehulling resulted in substantial reduction in the frequency and
incidence of reported discomforts but pressure cooking also had
beneficial effects, probably because of the higher cooking temperature
attained.
- Ndubuaku VO, Uwaegbute AC, Nnanyelugo DO, "Flatulence and other
discomforts associated with consumption of cowpea (Vigna
unguiculata).", Appetite, v13, n3, Dec 1989, pp. 171-81.
