There can be nothing as embarrassing and painful as gas. It gurgles and squelches through the intestines during pauses in conversations, squeaking like a rusty door or roaring like an express train. It gets trapped by spasms causing pain or such gross bloating and distension that you can look like you’re five months pregnancy. It can be expelled from the mouth with the cavernous belch of a lion, but worst of all, it can escape downwards, silent, deadly at five paces or with a high pitched squeak that instantly identifies your shame.
Most of this gas is generated in the colon by bacterial fermentation of carbohydrate or protein that has escaped absorption in the small intestine and is an explosive mixture of hydrogen and carbon dioxide with variable amounts of methane and some nitrogen.
My first insights into the explosive capabilities of intestinal gas was gained on a camping trip when I was just 14 years of age. During one particularly riotous evening, one of my friends, John Bishop, offered to ignite his intestinal gas in exchange for a pint of beer. Later, we gathered around the tent and waited while John readied himself. The tent flaps then parted to reveal a white bottom, while seemed to hang there like a full moon. Brian prepared the matches. On the muffled command of ‘Now!’, he lit a match and held it close to the pale globe. There was hiss of gas, a slight flutter, and the whole field was instantly illuminated by a dragon’s tongue of flame that was just as quickly extinguished.
Pain sensation is not immediate. There was a pause, as our eyes adjusted to the dark. This was followed by a scream as a half naked figure rushed from the tent and half ran, half jumped across the field, heading for the river. Blowback! Please let this be a solemn warning to any of you who might be tempted to repeat this experiment at home.
In the early days of enoscopy, such explosions were reported during the removal of a rectal polyps using diathermy. In one such incident, so the story goes, the sigmoidoscope was expelled out the rectum with the force of a rocket, slamming the surgeon against the opposite wall of the operating theatre. As the dazed practioner slid slowly to the floor, the patient raised himself on one elbow, looked round and with wonderful understatement, said, ‘Gee doc, you could do someone an injury doing that.’
But for most people the greatest risk of inadvertent gas production is psychological embarassment and occasioned by the smell and of course the noise of the escaping gas.
So why should intestinal gas smell so bad? After all, carbon dioxide, hydrogen, methane and nitrogen are all odourless. The answer is that just as water carries the taste of orange juice dissolved in it, so odourless intestinal gases carry small quantities of volatile compounds such as cadaverine and putrescine, which are formed by the bacterial putrefaction of proteins as well as hydrogen sulphide, the gas of school chemical laboratories that smells like rotten eggs. Hydrogen sulphide is generated in the colon by sulphide producing bacteria that break down sulphur containing amino acids as well as sulphite preservatives.
And what produces the noise? The ‘farty’ noise is produced by the floppy walls of a relaxed anal canal behaving like a flutter valve, opening and closing as the gas escapes. But what about the toots and squeaks? Buglers increase the pitch of their instrument by increasing both the pressure of expulsion and the tension in their lips. The same principle works at the other end. So if you have gas in the rectum and are squeezing the anus to stop it being expelled, then any increase in abdominal pressure that might be caused, for example, by getting up from chair or laughing, forces the gas out and creates a loud toot!
Some entertainers have been able to turn this knowledge to their advantage. Joseph Pujol, whose stage name was ‘Le Petomane’ (‘le pet’ is the French word for ‘fart’), had discovered early in life how to suck air into the rectum by coordinated contractions and relaxations of the muscles of his diaphragm, abdomen and anal sphincter. Then by delicate adjustments of abdominal pressure and anal tension, he could play tunes and generate sound effects. Pujol’s ‘piece de resistance’ was Tchaikovsky’s 1812 Overture complete with cannonade. It never failed ‘to bring the house down’ and he soon became a star turn at Le Moulin Rouge in Montmartre. Leopold, King of the Belgians was a notable fan.
Not many of us would have the confidence or the desire to turn flatulence into an art form. Neither are we as ‘gung-ho’ about farting as Robbie Burns, who advised his readers, ‘Where’re ye be, let ye’r wind gang free’. Most of us strive to contain our wind in company. Not to do so is indicative of a singular lack of social grace. So it’s not so much the actual expulsion of wind that is the problem, it is what it represents; the loss of control, a lack of social competence, a deficiency of manners and even dirtiness. Such notions were inculcated in most of us at a very early age!
But let’s get back to the science. How much gas do we evacuate from our colons? Doctor Janet Tomlin, who had the dubious privilege of measuring colonic gas expulsion, while working under my supervision for her PhD back in the dark ages. Using a rectal tube attached to a gas proof bag, and tested in the bath for gas leaks, she found that her ‘normal’ volunteers expelled between 200ml and 2 litres of gas a day depending on the diet they consumed.
Excessive flatulence frequently associated with intestinal illness. Any condition that impairs absorption of protein or carbohydrate, such as coeliac disease, pancreatitis, lactase deficiency or small intestinal bacterial overgrowth, can increase gas production. Farting is also an embarrassing feature of IBS and is caused by a combination of intestinal sensitivity, rapid small bowel transit (which would restrict absorption of protein and carbohydrate) and consumption of significant amounts foods containing poorly absorbed, rapidly fermented carbohydrates (FODMAPs). Indeed, the world’s gasiest man, the eponymous Mr Sutalf (Sutalf is flatus spelt backwards) had lactase deficiency and IBS and was recorded to fart 144 times in a single hour, generating enough gas to launch a weather balloon.
Farting in IBS is not only a feature of those with diarrhoea and rapid transit, it may also afflict those with constipation because they have a extra large pool of bacteria in the colon fed by the soluble fibre (methylcellulose and isphagula husk) and unabsorbed sugars (lactulose syrup and prebiotics) that are used to treat the resistant bowel. The observation that people with constipation tend to harbour greater concentrations of methanogenic bacteria might, however, reduce gas production since conversion of carbon dioxide and hydrogen to methane occupies less volume (but might increase risk of explosion on exposure to naked flames).
So what can be done to reduce or modify the expulsion of gas? There are three approaches: diet, drugs and behavioural therapy. Since most gas is generated by poorly absorbed starches and sugars, it would seem sensible to reduce the intake of foods that contain fermentable carbohydrate.
Beans, beans the musical fruit; the more you eat, the more you toot! The flatulent properties of beans have been immortalised in the Hollywood film, Blazing Saddles, but onions plums, prunes, apples, pears, reheated potatoes, cereal fibre and Jerusalem artichoke are also very gassy. These are the foods the comprise dietary fibre and FODMAPs and as such are generally reckoned to be healthy, helping people to lose weight and reduce plasma lipids and blood sugar levels. So everything has its down side. But if it is the volume of gas that is the problem, then restricting foods containing FODMAPs will certainly help. If, however, it’s the odour that causes offence, cutting down the amount of meat in the diet from the diet can also help.
Many products claim to reduce intestinal gas. Charcoal biscuits have been used for many years and claim to adsorb the gas onto the charcoal matrix (www.charcoal.uk.com). Products containing the antifoaming agent Simethicone reduce the surface tension of gas bubbles in the gut so that small bubbles join to produce big bubbles which are more easily expelled. So they might reduce bloating by increasing farting. while they might re Beano (www.beanogas.com/) contains enzymes that break down the starches in beans before they can be fermented in the colon By changing the composition of colonic bacteria, probiotics might lead to a reduction of flatulence in some people, but in others they might actually cause more gas. Capsules containing peppermint (Colpermin or Mintec) may also help, not because they reduce the production of gas but because the gas generated smells more sweetly of peppermint.
Some companies even produce underwear with a gusset that contains fart filter of activated carbon. They are hardly a fashion statement but they may nevertheless be a useful aid to socialisation.
There is no easy answer for most people with gassy symptoms. Relaxation and complementary therapies, that help to build confidence, may reduce the sensitivity and reactivity of the colon allowing more gas to be retained and absorbed instead of voided. For people who work in an enclosed office, it may be useful to take frequent loo breaks or walks to expel the gas.
But symptoms frequently express meaning and there can be few more meaningful symptoms than farting. So for patients whose gas expulsions resist all dietary or behavioural modifications and do not respond to medications, it can be useful to address the meaning – whether this be fear of company, the seeking of attention or even expression of disapproval or anger. Gas leaks can be dangerous whatever the cause!