Who ya gonna call? GasBusters. (Cover Story).

Got a question about gas? Michael Levitt is, arguably, the best person on earth to answer it.

The gastroenterologist at the Minneapolis Veterans Affairs Medical Center has authored dozens of articles on the subject. From the direct ("Identification of gases responsible for the odor of human flatus and evaluation of a device purported to reduce this odor") to the philosophical ("An understanding of excessive intestinal gas") to the provocative ("Colonic gas explosion--is a fire extinguisher necessary?"), he has written, seen, and sniffed it all. Well, almost all. In the odor study, he hired other people to judge the smell and rate the intensity of each "passage" collected by 16 volunteers. "The judges got paid better than the participants," deadpans Levitt.

When it comes to figuring out what causes gas, Michael Levitt is the man to call. (That's not to say that you should call him. If Levitt fielded questions from the public, he'd have no time for his research.) Whether it's beans, milk, vegetables, or swallowed air, he has challenged anecdotes with topnotch experiments.

Much of Levitt's research has zeroed in on individual foods that have a bad rap as gas producers.

Milk

Milk ranks high on the list of foods that supposedly cause gas. Many people assume that the culprit is lactose intolerance--gas, cramps, and other symptoms caused by an inability to digest the sugar (lactose) in milk. It's those people that Levitt studied.

"We didn't take all comers," he explains. "We advertised for people who thought they had terrible symptoms ... people who thought they had the greatest intolerance."

Twice a day--once at breakfast and once at dinner--Levitt gave them a glass of either ordinary milk or lactose-free milk. (1) (He made it by doctoring regular milk with lactase, an enzyme that breaks lactose into its component sugars--glucose and galactose. The sugars don't cause symptoms.) And the study was double blind--neither Levitt nor the volunteers knew which milk they were drinking.

"Most of the participants felt that the symptoms would be so awful that they would have to leave the study," says Levitt. "But the symptoms were trivial. And we found no difference in symptoms when they drank milk with or without lactose."

Levitt isn't saying that lactose never causes gas.

"Our results shouldn't be construed to say that most people can drink a quart of milk at a time," he notes. "If you flood the large intestine with lactose, you'll get symptoms."

Slim-Fast

Levitt's study refers to it as a milk-based "nutritional supplement used in weight control programs," but any dieter will recognize it as Slim-Fast. Instead of eating food for breakfast and lunch, dieters mix the milk-based powder with a glass of fat-free milk.

"The company was getting complaints about gas," says Levitt. So they came to the gas expert to find out why.

Levitt gave ten women a serving of Slim-Fast at 7 a.m. and another at noon. (2) On some days they got regular Slim-Fast, which has about 14 grams of lactose (a glass of milk has 12 grams); on other days they got a lactose-free taste-alike. Sure enough, "small flatus frequency" catapulted from eight to 20, while "large flatus" leaped from three to ten on the days the women drank the regular Slim-Fast. (We didn't ask Levitt to expand on those definitions.)

Why?

"If you take milk without food, you're more likely to get gas, because food slows the milk down," he explains. "Without food, the lactose hits the large intestine in one shot." (The company now makes a lactose-free Ultra Slim-Fast, which dieters mix with water.)

So it's not just how much, but how quickly, lactose arrives in your gut that matters. The bacteria that live there release hydrogen and carbon dioxide when they ferment the lactose. But that's not a problem if you've had only one glass of milk with food. Some of the gases get absorbed and some are gobbled up by other bacteria.

It's only when you overwhelm the system--with either too much lactose or lactose too quickly--that you might want to put a "do not disturb" sign on your office door and plan a quiet evening alone.

"Everything in moderation," says Levitt.

Beans

Beans. Now there's a food with a bad gas rap. "The whole bean thing is blown out of proportion," says Levitt, no pun intended.

A company once asked him to see if its specially bred beans caused less gas than ordinary beans. The results:

"The amount of gas was underwhelming even in the ordinary beans," he reports. People had more hydrogen in their breath when they ate the ordinary beans than when they ate the specially bred beans, but they didn't complain in either case.

"If you want to cause bloating, distension, or too much farting, you have to give a lot of beans," Levitt concludes. (People who devote a career to studying gas apparently save the euphemisms for their published work.)

Beans cause some gas because some of their sugars are indigestible ... except by those famished bacteria in your gut. "But something beyond just the sugars in beans produces gas," says Levitt. "It's just nowhere near as much gas as people claim to have."

That would explain how entire cultures have subsisted on beans and rice for centuries. "An awful lot of people eat beans on a daily basis," he points out. "And they're surviving just fine."

Vegetables

Levitt hasn't tested broccoli, cabbage, and other vegetables, largely because people would know what they were eating.

"Milk is easy to test because you can disguise it," he explains. Ditto for the beans he studied. But so far, no one's figured out how to rid vegetables of their gas-producing elements (if there are any) without altering the taste.

"I don't know how much is folklore and how much is real," Levitt explains. "Almost no vegetables have been put to a double-blind test, and if a study isn't double-blind, I don't pay attention to it."

Why? "There's a huge psychological component to food intolerance," he explains. "Expectations are really important with eating."

And meals offer endless possibilities for analysis and blame. "That's the beauty of food," says Levitt. "Whenever you don't feel good, you can blame it on a previous meal. People say: `Oh, there must have been a little milk in those potatoes ... that's why I had gas.' It's a perfect scapegoat."

And the more people worry about gas, says Levitt, the worse it gets. "Sometimes, if we can just get people to get their brain off their gut--say, with an exercise program--they feel better. Others are really worried about colon cancer. Once we do a colonoscopy, their symptoms are suddenly gone."

Mylar Pantaloons

Of course, sometimes it's not all in your head. It could be right there in your gut ... or, worse, in the room. As one of Levitt's papers noted, "the social significance of flatus derives mainly from its odor." Indeed.

Yet, he adds, "previous studies have focused on the non-odoriferous components of rectal gas." That's partly because the odoriferous component is so small.

"It's the gas with sulfur that causes the odor," he explains. "The volume of sulfur gases is trivial, but their potency is high."

What can keep you from wishing there were a quick way out of an elevator? Levitt tried giving people activated charcoal--which binds the sulfur ... at least in test tubes. It didn't work. (3)

"If you treat a fart with activated charcoal, you take out the odor," he says. "But you can't give enough activated charcoal by mouth to bind all the sulfur in the gut. You'd have to eat a pound of it."

Activated charcoal is apparently rather indiscriminating. "By the time the charcoal binds to everything it wants to, there isn't enough left over to bind all the sulfur."

However, Levitt did test cushions lined with activated charcoal. (4) Each of his 16 healthy (and brave) subjects was issued a cushion inside a set of gas-tight Mylar pantaloons (to collect what managed to get through the cushion). Then Levitt fed the volunteers a hefty amount of pinto beans and lactulose, a poorly absorbed sugar, "to enhance flatus output." (You can tell when Levitt is writing and when he's speaking.)

He compared how much sulfur escaped into the pantaloons with or without the cushion. "I didn't think the activated charcoal layer would be adequate to absorb all of the sulfur," he recounts. "It was only a thin layer. But it worked." (The pantaloons aren't for sale, but seat cushions coated with activated charcoal are--see "Have Cushion, Will Travel.")

Another remedy: Pepto-Bismol or some other brand of bismuth subsalicylate. "It binds sulfur gases and reduces the odor in the intestine," says Levitt. "But it turns stools black, and you can't take it forever." The black color isn't harmful (when the bismuth binds the sulfur in your gut, it produces bismuth sulfite, which is black). But take Pepto-Bismol every day and you could end up with bismuth toxicity. It causes a dementia that can sometimes masquerade as Alzheimer's disease.

Unfortunately, there's no easy way to get rid of the sulfur in your intestines. "Sulfur is in the mucus that lines the intestines and bacteria can make sulfur gases from many foods," says Levitt. "We've manipulated the diets of rats and we can't change the amount of sulfur they produce." In rat studies, antibiotics knocked out the bacteria that produce sulfur, he adds, but that's not a practical solution.

Surprisingly, odor isn't the chief complaint that Levitt hears about from his (human) subjects.

Air Head

"The most common complaint I get is bloating and distension," says Levitt. Take the case of the "extremely flatulent patient."

"I had a patient who farted an average of 170 times a day. We collected all of his rectal gas, and it was all nitrogen, so we knew it was mostly swallowed air."

The guy was an air gulper. "Most people swallow three times as much air as liquid," says Levitt. "Some people belch it up, and some don't. This guy would try to belch and end up swallowing more air."

Other people don't have more gas ... it just feels like it. "In some patients, we do a CT scan and don't see more gas than normal," he says.

Those people may simply be more sensitive to the gas in their gut. "The gas may irritate their intestine or they may not move gas normally," he explains. "Maybe a segment of the intestine clamps down."

"Most of them say, `If I could just pass the gas, I'd be lucky,'" he adds.

Lucky them.

Michael Levitt is a gastroenterologist and associate chief of staff for research at the Minneapolis Veterans Affairs Medical Center. He has authored or co-authored more than 100 scientific articles on flatulence. Levitt is much in demand as a lecturer (his slide show is legendary).

RELATED ARTICLE: The bottom line.

* Dairy. If you think dairy foods give you gas, try drinking no more than one glass of milk at a time with food. You can also try a low-lactose brand of milk. Cheese has much less lactose than milk (process cheese has slightly more than other types). Check the label for "sugars" (which, for cheese, is the same as lactose) to see if a serving has more than a gram or two. Yogurt is also low in lactose (its friendly bacteria digest the milk sugar), but some brands contain added milk.

* Beans. Use canned beans or dried beans that are thoroughly cooked (undercooked starch can cause gas). Discard the cooking water (it contains some undigestible sugars). Try Beano, an over-the-counter enzyme that digests bean sugars.

* Swallowed air. Eat slowly, make sure that any dentures fit properly, and don't chew gum or suck on hard candies.

* Vegetables. Don't swear off any vegetable (or other healthy food) because you think it once gave you gas. It may have been coincidence.

* Odor-busters. Try a seat cushion that's lined with activated charcoal (see "Have Cushion, Will Travel"). It won't curb gas, but it should help trap odor-causing sulfur compounds. Another tip: Keep a book of matches in the bathroom (or wherever). Light one and wave it around before blowing it out and you shouldn't smell anything but the match.

* Over-the-counter drugs. Antacids and activated charcoal supplements don't work. Pepto-Bismol does, but it should only be taken occasionally (check with your doctor if you're taking blood-thinning drugs).

* Food additives. Avoid foods that contain Olean (the trade name for the non-absorbable fake fat olestra), quorn (a chicken and meat substitute made from fungus), and sugar alcohols (like sorbitol, mannitol, and xylitol). All can cause gas, diarrhea, and cramps.

RELATED ARTICLE: Have Cushion, Will Travel.

You may never experience the thrill of participating in a study on gas. But, thanks to UltraTech Products of Houston, you can now conduct your own research at home or the office.

The company has been shipping its Flatulence Filters to satisfied customers since 1994. (They used to call it the "Toot Trapper," but people thought the product was a practical joke.)

The inch-thick, inconspicuous gray or black tweed polyurethane foam cushion is coated with activated charcoal, which traps about 90 percent of the odor-causing hydrogen sulfide gas that it comes in contact with. Researcher Michael Levitt tested the Flatulence Filter in his studies (though he doesn't endorse any commercial products).

Put the cushion on your chair, have a seat, and you're ready for just about anything. (If anyone asks, just tell them you need more height to see your computer screen or you have a lower-back problem.) Use it at the office, at home, or when you travel. ("Barbara from Minnesota told us that she used hers on a 9-hour flight to Europe," says the company's Web site. "`Boy, was life more pleasant for the passengers.'")

We haven't tried the cushion, but it does come with a 90-day unconditional money-back guarantee (minus shipping costs). When the activated charcoal becomes saturated with sulfur--every 12 months or so, "depending on usage"--you'll need a new cushion. But for many people--and their family and friends--that's a small price to pay.

The filters are $39.95 ($34.95 for two or more), with a $5 per cushion discount if you order online, via fax, or by mail. For more information, including shipping charges, visit the company's Web site (www.flatulencefilter.com) or call [phone] or [phone] (it's a small company, so you may have to leave a message).

(1) Amer. J. Clin. Nutr. 65: 1502, 1997.

(2) J. Amer. Diet. Assoc. 101: 1447, 2001.

(3) Am. J. Gastroenterol. 94: 208, 1999.

(4) Gut 43: 100, 1998.