TORONTO - So you think your husband's a little too adept at playing the colonic calliope? Wish your sleep wasn't interrupted by a fusillade of flatulence?

Well, if you think you've taken up residence in Beantown but he insists his output is normal, you can both at least take heart from the fact that debates like yours are raging all over.

You both should know this as well: Whether it takes the form of stealth bombers or noisy bottom burps, flatulence is a normal byproduct of the human body. Everybody farts, multiple times throughout the day and night.

But the whens and the hows can turn a basic bodily function into an inconvenient, unpleasant or downright embarrassing occurrence. And that leads some people to question what is normal and whether there's any way to turn down the tap, as it were, on the frequency, noise or odour quotients.

The fact of the matter is that while humankind has learned how to split the atom, manipulate genes and travel to the moon, it doesn't know all that much about how to reduce the production of natural gas.

"I know a lot about gas,'' says Dr. Michael Levitt, the American gastroenterologist who has unravelled much of what is known about human flatulence.

"I really can't treat anybody.''

Levitt is a veritable gas guru, a leading expert on the underappreciated field of flatus -- intestinal gas that escapes via the southern route. He admits his unusual expertise has put his three kids (one of whom is economist and "Freakonomics" co-author Steven Levitt) through expensive universities.

Levitt has gone to extraordinary lengths to plumb the mysteries of flatulence. He's captured farts in specially made Mylar pantaloons, measured the cocktail of gases they contain, even conducted a study devised to get to the bottom of what may be the most contentious question in the field: Which gender emits the smelliest farts?

So what have he and others learned about the fine art of flatulating?

It's a pretty common occurrence. Studies in which volunteers tracked their gas passage suggest people fart 10 to 20 times a day, with some hitting the 30, 40, even 50 mark, says Levitt, who is with the VA Medical Center in Minneapolis, Minn.

An Australian study that followed a group of men and women for a couple of months concluded men let rip on average 10 times a day, while women lag with eight emissions.

But producing less gas may create another problem for women -- and the people around them. Levitt's research suggests women's flatulence is more ... aromatic.

The study was the first ever attempt to provide an objective evaluation of the odour of flatus, Levitt explains. Volunteer judges, blinded to the identity of the generating gender, were asked to rank the potency of the end product.

Volunteer producers -- primed by a diet of pinto beans -- farted into aluminum bags via a rectal tube. The contents of the bags were measured for volume and for sulphur concentration. (Sulphur gases give farts their foul odour.) Syringes full of gas were withdrawn from the bags and wafted by the nostrils of the unfortunate judges.

"Some journal reviewed the worst jobs ever performed in science and this became the number 1,'' Levitt says with a chuckle.

"Now I might say the judges were paid well. Some of them complained of being dizzy and having a headache at the end of session.''

The conclusion: "Women had more sulphur gas and were judged to have more potent odour.''

Sulphur gases make up a tiny fraction of the overall volume of farts, Levitt says. But if that punch is concentrated, well, watch out.

"Individual passage of gas by males is appreciably greater than the individual passage by females -- in volume,'' Levitt explains. "So females could have a higher concentration of sulphur gases but the total amount passed per passage would be about the same.''

But who complains most about a partner's farts? Again, the distaff contingent takes the prize.

"It's often the women who are bringing the husband and saying: 'He's got a problem with gas.' And he says: 'No I don't,''' says Dr. Bruno Salena, a gastroenterologist at McMaster University in Hamilton.

Levitt concurs: "When I go to various parties, etc., I've never had a male complain about the gas passage of his female partner. But I've had so many complaints from the opposite direction it's ridiculous.''

In the main, flatulence is made up of five gases -- nitrogen and oxygen, which are swallowed while talking, chewing or drinking fizzy beverages, and carbon dioxide, hydrogen and methane, which are produced in the gastrointestinal tract during digestion of food.

Gas produced or trapped in the intestine only has three possible routes it can follow. Some will be absorbed into the body. Some will be burped out. And some will pass as flatulence.

People who lack bacteria that break down certain food components -- say lactose, the sugar in milk or some of the sugars in carbohydrates -- may produce more gas when they consume those foods.

That explains the potency of beans. They contain sugars humans can't break down. "So it's automatic that they're delivered to your large intestine, these sugars, where they churn out and make gas," Levitt says.

As for the noise, well, that's a product of restriction and pressure, says Salena, likening the process to whistling.

"Depends on the variables: the volume and pressure and the restriction," he explains.

"It's like making a sound with your lips, blowing air through your lips. And you can make that sound by some restriction and pressure. Similarly it (farting) is a combination of restriction and pressure. So it's a vibration of basically tissue, just like the lips."

As for cutting back on flatulence production, Salena suggests trying to reduce the amount of swallowed gas. Levitt is pessimistic about that option, insisting breaking that habit is hard to do. That's because people who swallow air are generally unaware they are doing it, he says.

Diets with extremely low carbohydrate intake produce little gas, but are hard to live on, Levitt notes. And many of the foods those regimes eschew should be part of a healthy diet, Salena says.

Maybe years of exposure to the subject have inured Levitt, but he says he doesn't give a hoot about the occasional toot.

"I don't worry one bit about gas. And I don't worry one thing about what I eat. I eat everything.''

Some weird factoids about flatulence through the ages:

  • Blue angels: Only certain people have bacteria in the gastric systems that produce methane, Dr. Levitt says. And only methane-producers can perform the time-honoured frat house trick of igniting a blue flame when they hold a match to an escaping fart.
  • Musical toots: In the 1800s Frenchman Joseph Pujol apparently became so adept at controlling his flatulence flow he could sound musical notes. Called "le Petomane'' _ the fartiste _ he was reputedly the highest paid performer in France at his prime.
  • Colonic explosions: In the early days of colonoscopies, attempts to burn off polyps in the colon ignited explosive hydrogen gas in the colon of several unlucky people, sometimes with tragic results. The colon-cleansing preparations people now take the night before a colonoscopy have solved the problem. Says Levitt: "I've never heard of an explosion in someone who's had a decent prep. But until they used these prep solutions, there was a problem with explosions.''