Reviewed By Michael Smith
It's happened to everyone at least once. In an awkward silence on a date, or during your fifth grade clarinet solo, or in the middle of a business presentation, your body suddenly betrays you. You burp. Or your stomach begins to growl and roar. Or worst of all, you have -- to put it delicately -- an outburst of intestinal gas.
But what causes these noisy, embarrassing, and sometimes foul-smelling eruptions? And is there a way to prevent them?
How Common Is Gas?
Gas is a great leveler. From the pauper to the king, from the slovenly frat boy to the prim grandmother, everyone has intestinal gas.
"We've all got gas, whether we admit it or not," says C. Mel Wilcox, MD, professor of medicine at the University of Alabama and spokesman for the American Gastroenterological Association. "But because everyone is different, some people have more than others."
According to the National Institutes of Health, the average person passes intestinal gas from 14 to 23 times a day and produces about 1 to 3 pints of the stuff.
That may be more than you expect. Many people who believe that they are excessively gassy actually have perfectly ordinary amounts, says Steven Edmundowicz, MD, chief of endoscopy at Washington University School of Medicine in St. Louis. However, it may be that it's just more distressing -- both emotionally and physically -- to some people than it is to others.
So where does gas come from? There are two major sources: some comes from air that you swallow and the rest is a by-product of digestion.Eating the Air
For the most part, burping is caused by air that you swallow. Aside from teenage boys engaging in belching contests, most of us don't swallow air on purpose. But eating air is easier to do than you might think. You can increase the chances of swallowing air by:
- Chewing gum
- Drinking through a straw
- Sucking on hard candies
- Drinking a lot of carbonated beverages
- Eating or drinking too quickly
- Wearing loose dentures
In addition, any medical condition that might cause you to swallow frequently can increase the amount of air you get into your stomach. For instance, allergies or sinus infections that cause postnasal drip can make you swallow more often. That may increase the amount of gas in your system.
Edmundowicz tells WebMD that people with severe heartburn are also likely to swallow air. The natural reaction to the backwash of stomach acid into the esophagus is to swallow in order to force the acid back down. The more you swallow, the more air gets into your stomach.
Some people develop an unconscious nervous habit of swallowing. "There are a lot of closet air swallowers out there who don't realize that they're doing it," says Wilcox.Bacterial Fermentation
Some of the air that you swallow goes through the intestinal tract and out the other end. But the major source of intestinal gas derives from the action of harmless, naturally occurring bacteria in your intestine.
Gas is a by-product of bacterial breakdown of undigested food that makes its way to the large intestine. Most of the gas is hydrogen, oxygen, nitrogen, carbon dioxide, and, in about one-third of people, methane. The signature stink of intestinal gas comes from sulfur.
The volume of intestinal gas is directly related to the amount of undigested food that goes into the large intestine. If you're eating things that can't be absorbed by the small intestine, or if your small intestine can't absorb certain foods normally, the bacteria in the large intestine will pick up the slack and manufacture more gas in the process.
The Growling Stomach
Intestinal gas can also cause the familiar sounds of the "growling stomach," a term that's actually a misnomer, says Munsey Wheby, MD, president of the American College of Physicians.
"It's not usually the stomach making the noise," says Wheby, who is also senior associate dean and a professor of medicine at the University of Virginia School of Medicine. "Instead, it's caused by the intestines as they contract."
Everyone knows that a growling "stomach" can mean that you're hungry. But the noise often stems from the movement of air through the intestines, whether there's food there or not. So if you've been swallowing a lot of air, or if you've been eating things that your small intestine can't digest, you may hear some grumbling, or even a whole symphony of bizarre and embarrassing noises.
But like burping and flatulence, occasional growling from the intestines isn't anything to worry about, says Edmundowicz.
What Foods Cause Gas?
Obviously, some foods cause more gas than others. As any schoolboy will tell you, the most notorious offender is baked beans, but there are plenty of others, including grains (for instance, the word pumpernickel is believed to stem from Middle German and mean, roughly, "goblin that breaks wind").
Any food that is high in soluble fiber, for instance, is only broken down by bacteria in the large intestine, so that can mean more gas. Foods that may cause gas include:
- Vegetables such as cauliflower, broccoli, cabbage, brussels sprouts, onions, artichokes, and asparagus
- Fruits such as apples, pears, and peaches
- Whole grains, such as whole wheat and bran
- Sodas and fruit drinks
- Foods with sorbitol, often used as a sweetener in sugar-free gums and candies
As you may have noticed, many of those foods are the bedrock of healthy diets.
"People sometimes do get confused when they find out that a healthy high-fiber diet with lots of fruits and vegetables can cause excess gas symptoms," says Edmundowicz.
Fruits, vegetables, and grains are important for digestion in other ways, so if you have gas, be cautious when trying to eliminate healthy foods from your diet. You may just need to eat a little less to ease your symptoms.Cutting Out the Cheese
Some people may have extra gas because can't digest certain foods normally. For instance, people who are lactose intolerant are missing the enzyme that processes lactose, the main sugar in dairy products. Because they can't digest it in the small intestine, the bacteria get a hold of the lactose in the large intestine, creating gas.
Although lactose intolerance is a common condition, especially among people of African, Native American, or Asian descent, you shouldn't immediately decide to cut out dairy products if you have excess gas.
"In my opinion, lactose intolerance certainly exists," says Wilcox. "But I think it's rarer than people think as a cause of symptoms."
Wilcox has seen many patients who have heard about lactose intolerance and diagnosed themselves. But even after eliminating dairy products, their symptoms linger. Cutting out dairy without good reason can lead to other problems in the long run, such as osteoporosis from the loss of calcium in the diet.
So if you're having excess gas, you shouldn't abruptly cut all dairy from your diet. Instead, see your doctor and talk about it. He or she might order some tests to find out. Edmundowicz also suggests that you try a more measured approach to zero-in on the particular foods that might be giving you trouble -- such as eliminating one food at a time and re-evaluating your symptoms.
Although lactose intolerance may be the best known, there are other types of known food intolerances. For instance, fructose intolerance is an inability to digest a different sugar that's in some vegetables and fruits and also used as an artificial sweetener.
But the individual reactions that people have to various foods are so diverse that they can't be categorized. For instance, once person may notice that peppers give her terrible intestinal gas, while another can't eat onions for the same reason.
Some of your digestive symptoms -- such as flatulence, bloating, and cramping -- may depend on what particular strains of bacteria have or have not set up shop in your large intestine. But that's probably not the whole story.
"We just don't have scientific and physiological explanations for some of these reactions," says Wheby.
Wilcox agrees. "It all just depends on your make-up and what you eat," he says, "and you learn what to avoid by trial and error."
How Can I Reduce my Gas?
Ultimately, there's only so much one can do to reduce the amount of gas you have. Everyone has to contend with some belching and intestinal gas every day.
But if it's really bothering you, or if you feel that the amount of gas you're producing is excessive, there are some steps you can take. All three experts agree that the most important steps are making changes to your diet by:
- Avoiding anything that might increase your chances of swallowing air, such as smoking, drinking through straws, and eating too quickly
- Avoiding or cutting down on problematic foods, such as carbonated drinks, beans, and some raw vegetables
- Considering a food diary. If you can't figure out what may be causing your increased gas, try keeping a journal of what you eat. You may find one or two foods that seem to increase your symptoms.
There are countless products sold in drugstores that may give you some relief, including antacids and digestive aids. But Wilcox and Edmundowicz caution that they may not help much.
"Antacids have very limited effects," says Edmundowicz. While simethicone, an ingredient in many antacids, seems to help some people with heartburn, it won't help with intestinal gas.
For people who are intolerant to lactose or the sugar in beans, enzymes are sold in over-the-counter products such as Lactaid and Beano, respectively, to help with digestion. However, their effectiveness varies from person to person, say Edmundowicz and Wilcox.
On the whole, Edmundowicz suggests that people use whatever over-the-counter or home remedies that help. "Because these symptoms aren't medically significant most of the time, we encourage people to use any safe remedy that works," he says.
When Should I See a Doctor?
Most of the time, gas symptoms aren't anything to worry about, but getting checked out is always a good idea. You should definitely see a doctor if:
- You notice new symptoms
- Your symptoms keep getting worse
- Your symptoms are associated with pain, vomiting, or weight loss
Certain conditions, such as Crohn's disease or tumors, can cause blockage in the intestines and increase gas symptoms.
However, if you've always had gas and you're not having more serious symptoms as well, you probably don't have to worry, say Wilcox and Edmundowicz.
"People come in with complaints about gas and want to be diagnosed with something," says Wilcox. "I think that's how Americans tend to be. But for a lot of these symptoms, we just don't have an answer. It just depends on the individual."
So for most of us, coping with gas -- while noisy, embarrassing, and sometimes malodorous -- is just a normal part of life.
Published Jan. 19, 2004.
SOURCES: Stephen Edmundowicz, MD, chief, endoscopy, Washington University School of Medicine, St. Louis. Munsey Wheby, MD, senior associate dean; professor, medicine, University of Virginia School of Medicine; president, American College of Physicians. C. Mel Wilcox, MD, professor, medicine, University of Alabama, Birmingham; spokesman, American Gastroenterological Association. The National Digestive Diseases Information Clearinghouse (National Institutes of Health) web site. The American College of Gastroenterology web site. Karry A. et al. Journal of the American College of Nutrition, 2001; vol 20: 198S-207S. Tuula H. et al. Journal of the American College of Nutrition, 2000; vol 19: 165S-175S.
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