麻豆传媒

WHATEVER you鈥檙e 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鈥檙e probably too embarrassed to ask. We鈥檙e 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鈥檚 practically everything 鈥� ).

鈥淛oseph Pojul made a career entertaining theatregoers with his聽fartistry鈥�

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 , 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 . However, Terry Bolin at the University of New South Wales, Australia, found that 鈥� which may result from a female tendency to suppress emissions.

In keeping with such wide variations, other research indicates that healthy people pass between . 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 鈥渇latulogenic diet鈥� have been found to produce two-and-a-half times as much gas 鈥減er anus鈥� as they do on their normal diet.

What鈥檚 in a fart?

Even the untrained nose can ascertain that the composition of flatus . The percentage of swallowed gas can be far higher for people with . 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 , which together account for less than 1 part in 10,000 of an expulsion of wind. With help from two stalwart 鈥渙dour judges鈥�, he discovered that a fart鈥檚 potency derives from hydrogen sulphide, the 鈥渞otten-egg鈥� gas. The overall bouquet, however, depends on how this intermingles with two other main culprits: methanethiol, which smells of 鈥渄ecomposing vegetables鈥�, and the 鈥渟weet鈥� odour of dimethyl sulphide.

Are silent ones deadlier?

Although sometimes described as a 鈥渂ottom burp鈥�, a fart is more like a whistle. The greater the volume and pressure of air passing through your rear, the louder the noise. This 鈥渋nstrument鈥� has been played to considerable effect by professional trumpers, most notably the Frenchman , 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鈥檚 flatus contained significantly more pungent hydrogen sulphide than men鈥檚, and his .

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

Are farts really flammable?

Some people鈥檚 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, 鈥渟melly鈥� or 鈥渋nflammable鈥�. 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鈥檚 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 鈥渋nflammable鈥� 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聽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聽evidence that smelly , 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. 鈥淗ydrogen sulphide is as toxic as cyanide,鈥� he says. 鈥淕et rid of it.鈥�

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

In any case, the experts agree that for most of us, flatus is nothing to worry about 鈥� a 鈥渂lessing in disguise鈥� 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 鈥淐learing the air鈥�