Excessive gas

 | January 1, 2008

Excessive gas

Aside from causing embarrassment, too much gas in the digestive system can result in considerable pain, bloating, and discomfort — symptoms that may appear on their own or in conjunction with functional dyspepsia or irritable bowel syndrome. Sometimes, you may even hear and feel air and liquid swirling around inside. But there are practical steps you can take to control this problem.

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Where does gas come from?

There are only two ways for gas to get into the GI tract. Either you swallow it (aerophagia), or it's manufactured in the gut (often producing flatus).

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Aerophagia

Aerophagia — excessive swallowing of air — produces belching or burping. The upper gastrointestinal gas that erupts from the mouth comes from swallowed air that forces itself back up. There are actually two kinds of belching. One is a fairly innocuous condition that stops on its own about an hour after eating and is caused by air swallowed while eating. The other is more persistent and is caused by constant air swallowing, a nervous habit most people don't even know they have.

Technically called eructation, belching occurs when the upper esophageal sphincter relaxes and lets the pressurized gas that has been swallowed escape from the mouth. A study has found that healthy young people belch an average of 11 times in 20 hours, excluding mealtimes.

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Flatus

Also known as flatulence, this term describes gas that escapes from the rectum. The gas is mostly the byproduct of the fermentation of undigested food by bacteria in the colon. It contains carbon dioxide, hydrogen, and, in some people, methane. Tiny amounts of volatile chemicals produced by bacterial metabolism of residual fats and proteins are responsible for the distinctive foul odor of flatus.

Gas that escapes from the far end of the GI tract may be natural, but nowhere is it an accepted part of society. The average human intestine holds 0.1 to 0.2 liters of gas, but researchers have found that in 24 hours, production of flatus averages 2 liters. This gas originates in the intestine, and its quantity and composition depend largely on the foods you eat. Studies using hydrogen breath testing have found that up to one-fifth of the complex carbohydrates eaten by average, healthy individuals is turned into gas.

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A gas primer

The air we breathe is made up mostly of nitrogen (N₂ ) and oxygen (O₂ ), the gas the human body needs to sustain life. After being swallowed, air enters the GI tract. As it moves along, its makeup changes as oxygen passes into the blood and nitrogen is removed from the blood. Another intestinal gas is carbon dioxide (CO₂ ), a byproduct of a chemical reaction with acid in the stomach. Hydrogen (H₂ ) is released in the colon when undigested carbohydrates undergo bacterial fermentation.

Bacteria in the gut produce foul-smelling gases when they ferment undigested foods that have not been absorbed in the small intestine. These foods consist mostly of carbohydrates, sugars, and fats. The carbohydrates found in high-fiber foods, such as beans, broccoli, cauliflower, and Brussels sprouts, are the worst culprits. These foods release gases such as methane and hydrogen sulfate, which smells like rotten eggs. The worst odor is related to strong-smelling sulfurs that make up just 1% of flatus.

Methane is detected in about one-third of adults. Studies show that Americans and Europeans are more likely to produce methane than Asians are, possibly because of diet. Women also produce more than men do. Genes may play a role in methane production, as the trait is passed along in families.

Additional carbon dioxide is produced in the colon as the byproduct of bacterial fermentation of unabsorbed sugars and starches. Eating beans will substantially increase CO₂ production, as will taking sodium bicarbonate for heartburn. Thus, it doesn't make sense to use bicarbonate-containing seltzers for gas.

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Gas in the intestine

You hardly notice gas when it enters your digestive system, but once it's there, the discomfort can be intense. As for its escape, everyone knows the effect created by powerful gaseous emissions.

People who suffer the symptoms of gas pain and bloating usually have the same volume of gas as anyone else, or just a little bit more. But it affects them more because they are more sensitive. Some people with chronic gas pain have impaired peristalsis and significant reflux of gas from the small intestine into the stomach.

Although gas pain and bloating are usually not significant health concerns, it is important to see a doctor if the symptoms persist because they are occasionally a sign of some more serious condition. Severe distension immediately following a meal is called magenblase (stomach bubble) syndrome and may be mistaken for heart pain. Splenic flexure syndrome is a painful spasm in the left upper abdomen below the rib cage, produced by localized areas of trapped gas in the colon.

Borborygmi is an onomatopoeic word that refers to sounds created by peristaltic activity. Although disconcerting to the person whose insides are grumbling, it often goes unnoticed by anyone else.

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Eating habits and gas

Throughout history, certain foods have been notorious for producing gas (see "Foods that may cause gas"). Beans are the most obvious example. Beans contain the complex carbohydrates stachyose and raffinose, which the intestine can't absorb but the bacteria in the colon love. The problem is most serious in people who have been eating a low-fiber diet and switch to a diet rich in beans and other high-fiber foods. Their digestive tracts don't have enough of the enzymes needed to digest bean sugars, which now pass undigested into the lower intestine where the bacteria metabolize them and generate gas. If people eat beans on a regular basis, the problem usually lessens as the body begins to produce the enzymes it needs.

People who are lactose intolerant often describe distressing flatulence if they consume milk products (see "Understanding food intolerance"). Other factors, such as disturbances in motility or metabolism, also influence how often and how much flatus is passed. For instance, people with slowed intestinal motility may produce more gas simply because bacteria have more time to work their magic on complex carbohydrates. Gas production may also increase when people take antibiotics, which lead to changes in the types of bacteria in the colon, or when the acidity level in the bowel goes down.

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Diagnosing and treating aerophagia and flatus

The important thing for a doctor to consider in diagnosing a belching, bloating, or flatulence problem is whether it's occurring alone or in conjunction with one or more of the various functional GI disorders or a more serious GI illness. He or she should be alert to problems that may suggest organic disease, such as weight loss or anemia. Of course, a physician may be able to determine quickly that the problem is the result of eating too many beans or swallowing too much air. In most cases, evaluating complaints of gassiness will not require extensive diagnostic testing.

To assess your gassiness, your doctor will first question you about your symptoms and dietary patterns. If upper GI bloating and belching are the major problems, excessive air swallowing may be the culprit. The doctor will ask about possible lactose intolerance as well as habits such as gulping down meals, drinking carbonated beverages, sipping through a straw, chewing gum, smoking cigarettes, or chewing tobacco.

The doctor will also want to know about anxiety and psychological problems that may contribute to air swallowing and predispose people to symptoms, including gas and cramping. Likewise, he or she will want to review the medications you are taking, since some — especially drugs that are encapsulated with a sorbitol filler — can induce gas, bloating, and diarrhea.

An abdomen distended with air can be detected by listening for a hollow sound when tapped. Organic causes of intestinal distension include obstruction of the bowel or fluid or a mass in the abdomen. But other signs usually accompany these more serious problems, and they usually can be readily confirmed by an imaging study such as a CT scan. Some, such as gastric distension, can be identified with a simple abdominal x-ray. Some doctors may want to run a lactose absorption test or hydrogen breath test to check for lactose intolerance.

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Treating belching

The key here is to reduce the amount of air you swallow. Quitting chewing gum and smoking — and maybe trading in loose dentures for snugger ones — should cut down on air gulping. One easy fix is to avoid carbonated drinks and whipped desserts, which trigger burping. Some people swear by including certain foods in the diet, such as brown rice or barley broth. Papaya and pineapple are also said to help. Make sure to chew foods slowly, avoid washing food down with liquids, and try to eat smaller meals. And don't eat when you are anxious, upset, or overtired. If you have aerophagia, antidepressants and tranquilizers may calm the nerves or lessen anxiety, but they must be used carefully and only under a doctor's close supervision.

Taking a brisk stroll after eating, rather than taking a nap, is a good idea. It promotes gastric emptying and helps relieve the bloated feeling. When it's time to go to bed, try sleeping on your stomach or right side to aid in the escape of gas and alleviate fullness.

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Treating flatulence

The first step is easy. Stop eating the foods that cause gas: beans, fruits, and other complex carbohydrates, as well as the artificial sweetener sorbitol. But don't eliminate all fruits and vegetables, because these foods are the basis of a healthy diet. A product called Beano, which contains the enzyme alpha-galactosidase, can help metabolize difficult-to-digest complex carbohydrates when taken before meals. And preparations containing the pancreatic enzymes lipase, trypsin, and amylase may reduce gassy emissions by helping to digest proteins, starches, and fats when taken with meals. These enzymes are sold over the counter in capsule form (a product called Super Digestive Enzymes is one example), at stores that sell nutritional supplements.

For some people, a drastic reduction in dietary sugars and some cutback in refined starches and wheat flour may help. Activated charcoal, a tasteless black powder, absorbs gas and for some people cuts down on gassiness, particularly after a high-carbohydrate meal. Occasional use is not harmful. Pepto-Bismol may reduce the odor of flatus.

Some people have had success with anticholinergics, drugs such as dicyclomine (Bentyl) and hyoscyamine (Levsin). These agents block nerves that stimulate the digestive tract. A course of the broad-spectrum antibiotic rifaximin (Xifaxan) may also help reduce flatulence, without side effects.

When all else fails, wearing a deodorizing and absorbing pad containing activated charcoal beneath one's undergarments doesn't stop flatulence, but it can prevent others from noticing it. A 2005 study in the American Journal of Gastroenterology found that such devices are moderately effective.

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Review Date: 2008-01-01

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