It's one of the most common -- and most socially unacceptable -- bodily functions. It's even awkward to talk about, unless you're a 4-year-old boy boasting about your prowess.

Nonetheless, everyone's got a fart story: The teacher who pretends an unexpected blast was really the sound of his shoe scuffing the floor. The high school date who attributes his passages to your sleeping dog. The woman who toots all the way down the aisle in church.

For some, flatulence is noticeable -- by sound or by scent -- a mere three or four times a day. But even if your intestinal blasts hit 30, which is not uncommon, it could be worse. "If we passed all the gas that we made, everybody would be farting a million times a day," says Michael Levitt, a gastroenterologist and director of research at Minneapolis Veterans Affairs Medical Center.

Levitt is an expert: He's been studying flatulence, the presence of gas in the intestine and stomach, for decades. He says the typical person's intestines process 10 liters of gas -- nitrogen, oxygen, carbon dioxide, hydrogen and methane -- every day.

The nitrogen and oxygen generally come from air that you draw into your digestive system. Just by swallowing the saliva in your mouth, for example, you've downed about 15 cubic centimeters (cc) of air. For people with a nervous habit of gobbling down air, that can add up to a bellyful of gas, Levitt says.

The other three gases are produced in the large intestine, primarily by bacteria. "These bacteria are starving to death, waiting for anything," says Levitt. Basically, any food that survives the initial digestive process gets fermented by these bacteria, and the result is a lot of gas. We don't pass most of it -- thank goodness -- because as soon as those hungry bacteria produce gas, others consume it. What little that's left over gets expelled. (Women's emissions are smaller than men's -- averaging 90 cc compared with 125 cc.)

The five major gases have little or no odor. Most of the unpleasant fumes come from trace amounts of sulfur in the intestine -- residue from meats and some other foods.

Dangerous? Not medically. But do you have an uncle who claims his gas can light a match? Well, Levitt says that in the 1980s, early colonoscopy procedures led to a few mini-explosions when stray electrical sparks reacted with intestinal hydrogen. That's why patients are required to fast -- and to drink large amounts of liquid to clean out the intestines -- before undergoing the procedure.

Mainstream Measures

There's no quick fix for excess flatulence, but if you present your primary care doctor with the problem, he or she will likely try to help you find the "gas triggers" in your diet. These often are hard-to-digest sugars such as lactose or fructose (which are particularly prevalent in some beverages, in dietetic candies and in chewing gum, especially the sugar-free kinds). More commonly recognized triggers are beans, cauliflower, broccoli, onions and cabbage.

In general, the more carbohydrates you eat, the more gas you'll produce. Vegetarians are likely to produce more gas than other people, especially when first switching to more legumes. Jennifer Grana, a registered dietitian with Lifestyle Advantage, the Dean Ornish diet program, says everybody who follows the Ornish diet (low fat, no meat, whole grains) initially produces a lot more gas, a discomfort that balances out in two to four weeks.

In trying to identify your triggers, it's important to consider not only what you just ate, but what you had eight or 12 hours earlier. So if you're feeling gassy in the morning, think about what you ate the day before.

Charlene Prather, a gastroenterologist and associate professor at St. Louis University School of Medicine, says about 80 percent of people complaining about their flatulence benefit from dietary changes. For example, lactose intolerance -- trouble digesting milk sugar, which can produce excess gas -- can be pinpointed with a breath test administered by your doctor. In such cases, dietary alterations and taking lactase (Lactaid) may reduce gas, though they probably won't solve the problem completely.

Sometimes the issue is not the excess gas itself but how it gets emitted, says Prather. "Many women lose anal sphincter control after childbirth," she says, and cannot delay release of their gas long enough to pass it in a private setting. In such cases, she teaches women to squeeze the anal sphincter without tightening the belly. For women who need extra guidance in getting started with these exercises, a physical therapist may be helpful.

Prather and Grana both suggest chewing food longer and taking time to enjoy each meal vs. gobbling on the run. If swallowed air is a problem, don't use straws, don't suck on hard candy and don't chew gum. Drinking more water and exercising can also help digestion, which can reduce gas.

In the "won't hurt, might help" category are several over-the-counter products: simethicone (brand names include Gas-X and Mylanta Gas), which breaks up gas bubbles, making them easier and less painful to pass; capsules of activated charcoal, which absorbs gas (but be aware that the charcoal will absorb medications, too); Beano, which contains an enzyme that neutralizes gas; and probiotics, which help establish healthy intestinal flora.

If you don't want to tinker with your bodily processes but just want to get rid of the odor, you can try a charcoal filter cushion. The Flatulence Filter -- formerly known as the Toot Trapper -- is available on the Internet; a cushion that's said to last for up to 18 months sells for about $40. A research team that included Levitt reported in a 1998 edition of the medical journal Gut that the filters absorbed about 90 percent of the odor generated by people who had eaten pinto beans.

Alternative Approaches

Like their mainstream counterparts, alternative practitioners suggest finding food triggers, eliminating swallowed air and trying over-the-counter preparations. They also recommend other options that have anecdotal if not scientifically conclusive evidence of effectiveness.

Mary Hardy, medical director of the Cedars-Sinai Integrative Medicine Medical Group in Los Angeles, recommends adding carminative herbs and spices to your diet. Among these ingredients, which aid in the digestion of foods likely to create excess gas, are chamomile, mint, ginger, fennel, cumin, coriander and oregano. To enhance digestion, Hardy, an internist who specializes in botanical medicine, also suggests animal-based enzymes, which are available by prescription, and plant-based varieties -- including bromelain (made from pineapple) and papain (made from papaya) -- which are available in health food stores.

Perhaps traditional cultures have the answer. In India a spice called hing is routinely used in bean dishes because it helps reduce gas, says Teresa Graedon, a medical anthropologist and co-author of the "People's Pharmacy" drug and health information books. "There are a number of things in the cooking process that other cultures are more tuned into," she says. In Mexico, black beans are always cooked with epazote, another carminative herb. The Chinese use fennel for what they call excess wind. "These cultures have traditional pairings" of foods that help keep flatulence in check, Graedon says.

Other cooking tips include a pinch of ground ginger in the lentil pot; adding fresh ginger to many foods; and boiling and soaking beans before cooking them.

Still, sometimes you need to find and avoid problem foods. Joe Graedon, a pharmacologist and Terry Graedon's husband and co-author, suggests keeping a "fart chart." "That's the only way to get a handle on it," he says. "Keep a fairly accurate food diary and [a log showing] when you pass gas," he says. "You discover surprising things."

Joe also suggests keeping a sense of humor about flatulence. "It's an attitudinal thing, the way you look at it. I think some cultures see it as sexually stimulating."

Terry's not so sure about that. Resources

* National Digestive Diseases Information Clearinghouse, a service of the National Institute of Diabetes and Digestive and Kidney Diseases: www.niddk.nih.gov/health/digest/pubs/whygas/whygas.htm and www.niddk.nih.gov/health/digest/pubs/gas/gas.htm

* American Gastroenterological Association: www.gastro.org/public/gas.html

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