Farting: The questions you’re too embarrassed to ask

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WHATEVER you’re celebrating, the holidays are a good excuse to eat, drink and make merry. Flatulence is one of the most immediate consequences of overindulging and a perennial topic of mirth. But it also raises genuine questions that you’re probably too embarrassed to ask. We’re here to help.

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Are some foods fartier than others?

Beans are not the only musical foods: flatus happens when we eat any complex carbohydrates. They are abundant in beans and pulses, but are also found in fruit and vegetables, dairy products, meat, alcoholic beverages and other goodies (yes, that’s practically everything – the list of foods that can reduce your toots is short and filled with caveats).

“Joseph Pojul made a career entertaining theatregoers with his fartistry”

These compounds cannot be broken down in the small intestine, where most foods are digested, so pass unadulterated into the colon. Here, they are set upon by some 2 kilograms of bacteria, including the deceptively cuddly sounding Firmicutes and Bacteroidetes, which ferment the recalcitrant foodstuffs. The inevitable by-product is gas.

Gut microbes are particularly perky when you indulge in festive meals, largely due to the glut of carbohydrates. However, turkey with all the trimmings packs a double punch. Brussels sprouts, onions, dried fruit, red wine and the bird all contain sulphates, which are the key component of the most noxious intestinal gases.

How much wind is normal?

This is a tough one because you have to rely on honest answers. Studies asking volunteers to monitor their own emissions suggest 10 to 20 toots a day is normal. However, Terry Bolin at the University of New South Wales, Australia, found that men let rip an average of 12 times a day to women’s seven – which may result from a female tendency to suppress emissions.

In keeping with such wide variations, other research indicates that healthy people pass between 0.4 and 2.5 litres of gas daily. Not all of this is food-induced, though. About half the total volume derives from swallowed gases. Still, what you eat makes a huge difference, so much so that regular punters given a “flatulogenic diet” have been found to produce two-and-a-half times as much gas “per anus” as they do on their normal diet.

What’s in a fart?

Even the untrained nose can ascertain that the composition of flatus is highly variable. The percentage of swallowed gas can be far higher for people with ill-fitting dentures or an addiction to fizzy drinks. These gases are mainly nitrogen and oxygen. The remainder, produced by gut bacteria, is mostly hydrogen, along with carbon dioxide and methane.

So what makes the stink?

As in any perfume, the aroma comes from tiny quantities of pungent molecules. Flatulence guru Michael Levitt at the University of Minnesota, Minneapolis, has traced its noxiousness to three sulphurous gases, which together account for less than 1 part in 10,000 of an expulsion of wind. With help from two stalwart “odour judges”, he discovered that a fart’s potency derives from hydrogen sulphide, the “rotten-egg” gas. The overall bouquet, however, depends on how this intermingles with two other main culprits: methanethiol, which smells of “decomposing vegetables”, and the “sweet” odour of dimethyl sulphide.

Are silent ones deadlier?

Although sometimes described as a “bottom burp”, a fart is more like a whistle. The greater the volume and pressure of air passing through your rear, the louder the noise. This “instrument” has been played to considerable effect by professional trumpers, most notably the Frenchman “Le Pétomane”, aka Joseph Pojul, who from 1887 made a career entertaining theatregoers with his fartistry. Pojul had taught himself to suck up air through his anus and expel it under pressure to create farts that were thunderous but fairly innocuous.

By contrast, low volume and pressure give rise to a more discreet trump. But is it more noxious? Perhaps. Levitt found that women’s flatus contained significantly more pungent hydrogen sulphide than men’s, and his judges rated it as smellier.

Women also tend to produce less flatus than men, perhaps because of suppression – suggesting they are also more likely to control the pressure of their emissions to avoid drawing attention. This logic hints that a fart’s bark may indeed be inversely correlated with its bite.

Are farts really flammable?

Some people’s are. Glenn Gibson, who builds working models of the human colon at the University of Reading, UK, says all farters fall into one of two groups, “smelly” or “inflammable”. About a third of us are in the latter camp, with methane-producing bacteria in our bowels acquired from our mothers.

Methane, otherwise known as natural gas, is odourless and highly combustible. In fact, at concentrations above 4 or 5 per cent, it is explosive, so it’s fortunate that the act of passing wind mixes it with air, diluting the methane to safe levels. Place a match close enough to the source, however, and the seemingly innocuous flatus of an “inflammable” can be made to ignite.

Is it better out than in?

Every day, your gut generates a whopping 20 litres or more of gas. But most of this is not destined to become flatus: almost all of it is either recycled by the bacteria in your colon or absorbed into your body and exhaled in your breath.

For the bit that remains, there is evidence that smelly hydrogen sulphide prevents inflammation of the gut lining, maybe reducing your risk of bowel disease and cancer. So perhaps it might actually be good to hold that fart in. Gibson is sceptical, however. “Hydrogen sulphide is as toxic as cyanide,” he says. “Get rid of it.”

What’s to be done?

Well, there are products that contain the same enzymes used by the bacteria in your colon. Take one with your festive lunch and it will get to work straight away, breaking down the complex carbohydrates into simpler sugars that are more easily digested in the small intestine.

If it’s not wind but the nasty niffs that bother you, Levitt has found that bismuth can help, and there are stomach-remedy products available that contain it. However, a daily dose is not recommended because they can irritate the gut. And stay away from those charcoal knickers advertised on international flights: for all their promise, they’re full of hot air.

In any case, the experts agree that for most of us, flatus is nothing to worry about – a “blessing in disguise” that indicates you have healthy gut bacteria. Besides, is there a better butt for a joke than a fart?

(Image: Modern Toss)

This article appeared in print under the headline “Clearing the air”

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