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Gas is a healthy sign

In medicine, it can be hard to talk about "passing gas from below" appropriately. If you use the medical word "flatus," you risk sounding stuffy. If you use the other "f-word," you can sound crude.

Euphemisms are not always clear. And yet flatus is important. It's a sign of a healthy gastrointestinal tract: the average person passes gas up to 20 times a day. The corresponding social embarrassment, though, has consequences.

An extreme example is the forced landing of an American Airlines flight in Nashville earlier this month after a passenger politely lit a match to hide an odor. But more typically, the fear of flatus either keeps a patient from going out in public, or becomes a matter of personal obsession that itself becomes a pathology.

So gas is worthy of attention.

Flatus either comes from swallowed air or fermentation of food. The fermentation is usually of carbohydrates and by the many types of bacteria, usually friendly, that live in our intestines. Bacteria actually comprise the bulk of the weight of stool.

The main gaseous products of fermentation are hydrogen, methane and carbon dioxide. Hydrogen and methane, of course, are flammable, the source of certain rumored practices involving lighters and brief explosions. (Please don't try it.) Nitrogen and oxygen are the two gases that are swallowed and appear in flatus.

If you were actually to collect your gas, you would be able to tell how much came from swallowing and how much from fermentation. This isn't done very often. However, it has been done at the University of Minnesota, a place where flatus seems to get respect.
Gastroenterologist Michael Levitt has been studying it for decades. His lab workers collect flatus from volunteers, who reportedly are well paid. These individuals, as reported in the literature, have rectal tubes placed, and flatus is collected in mylar bags. To ensure that the volunteers actually pass gas, they in at least one experiment were fed beans and the laxative lactulose.

The flatus is analyzed by gas chromatography. Also, the smells are judged for offensive qualities. There is only one way to do that. Therefore, the experimenters required a second set of volunteers, who are actually paid more.

This research process has determined that the offensive odors in flatus are caused by sulfur-containing chemicals, like hydrogen sulfide. However, few remedies are available to eliminate these sulfur compounds from stool and flatus.

Charcoal was a candidate, as it absorbs just about everything. Taking it orally doesn't seem to work much, and anyway puts you at risk of absorbing things you need, like vitamins. However, one can buy charcoal-containing underwear that does a relatively good job of reducing or eliminating odors.

Levitt's lab tested this. Charcoal pads, placed on chairs in offices for example, are not nearly as effective at trapping and eliminating the odor of flatulence as the charcoal pants, according to Levitt's research. Bismuth (Pepto-Bismol and other preparations) reduces the odor of flatus, but you shouldn't take it every day as it can build up and become toxic. So you might try it if you have a special date.

What else can we do about flatus? Many adults can't digest lactose, the main sugar in milk. By the time we grow up, the enzyme that digests milk sugar tends to disappear from intestines. So when the sugar reaches the intestines, bacteria ferment it into fatty acids and gas. You could try eliminating dairy foods for a few days to see if this helps. A supplement of the "probiotic" bacteria Lactobacillus might help decrease intestinal gas production and bloating.

In some people, swallowing air is a major cause of gas passage throughout the gastrointestinal tract. This can be helped by eating and drinking more slowly.

The enzyme Beano, put on carbohydrates before eating, can help reduce gas production. Tofu may have been invented as a way to consume bean protein without causing flatulence, and likewise wine a way to eat grapes safely.

In the end, we may be left with Benjamin Franklin's advice, which, to paraphrase, enjoins us to pass gas without shame.

Dr. Mike Merrill is an internist practicing in Buffalo. His column appears once a month on this page. E-mail your comments to him at

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