There can be nothing as embarrassing and painful as gas. It gurgles and squelches through the intestines during pauses in conversations, sometimes squeaking like a rusty door and sometimes roaring like an express train in a tunnel. It can get trapped by spasms causing pain and such gross bloating and distension that women can look as if they’ve acquired a five month pregnancy within the space of half an hour. It can rise up in the mouth and be expelled with a cavernous belch but worst of all, it can escape downwards, silent and deadly at five paces or with a distinctive sound that instantly identifies your shame.


Doctor Janet Tomlin, who worked in my laboratory, had the dubious privilege of measuring colonic gas expulsion by means of a rectal tube attached to a gas proof bag.  Her ‘normal’ volunteers expelled between 200ml and 2 litres of gas depending on the diet they consumed.  



Most of this gas is generated in the colon by the fermentation of carbohydrate or protein that has escaped absorption in the small intestine. Indeed the colon can be thought of a large fermenting vat of bacteria, converting sugars and starches and some protein to short chain fatty acids (mainly acetic acid, propionic acid and butyric acid), a little alcohol and a lot of gas. Colonic gas is predominantly 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 obtained on camping trip when I was just 14 years of age. During one particular riotous evening, one of my friends, John Bishop, offered to ignite his intestinal gas in exchange for a pint of beer. So later, back at the tent, he prepared himself, his bottom emerging pale like the risen moon from between the tent flaps, while we readied ourselves with the matches. On the muffled order of ‘Now!’, we lit a match and held it close to the pale globe.  There was hiss of gas, a slight flutter, and the field was instantly illuminated by a bright 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! So let this be a solemn warning to any who might be tempted to repeat this experiment at home.   



In the early days, explosions were also reported during the endoscopic 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 surgeon 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 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 skatoles, cadaverine and putrescine, which are formed by the bacterial putrefaction of proteins. Intestinal gas also contains very small amounts of hydrogen sulphide, the gas of school chemical laboratories that smells like rotten eggs. In the colon, hydrogen sulphide is generated from the breakdown of sulphur containing amino acids as well as the reduction of sulphite preservatives by populations of sulphide producing bacteria.


And what produces the noise? As we are all aware, the expulsion of gas from the anus can generate a variety of sounds. 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. As any trumpeter knows, the more tension there is in the muscles surrounding an orifice, the higher the pitch. So if a person is squeezing the anus and trying to stop gas being expelled, 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! But this need not always be such a disadvantage.



The entertainer, Joseph Pujol discovered early in life that by exquisitely timed contractions and relaxations of the muscles of his diaphragm, abdomen and anal sphincter, he could suck gas into the rectum and expel it at will. Not only that, but by delicate adjustments in its expulsion, he could play tunes and generate sound effects. His fame spread far and wide and under the pseudonym of ‘Le Petomane’ (‘le pet’ is the French word for ‘fart’) he was soon the star of Le Moulin Rouge, performing before the rich and famous. The King of the Belgians was a notable fan. Pujol’s ‘piece de resistance’, Tchaikovsky’s 1812 Overture complete with cannonade, never failed to bring the house down!


Not everybody is fortunate enough to turn their disability into an art form. But there again, not everybody would want to! Neither are people generally 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 graces.  So it’s not so much the actual expulsion of wind that is the problem, it is what it represents; 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!



Farting is frequently associated with intestinal illness, particularly conditions, like celiac disease, pancreatitis, or lactase deficiency, that reduce absorption of carbohydrate or protein.  Indeed, the world’s gasiest man, the pseudonymous Mr Sutalf, had lactase deficiency.  He was recorded to fart 144 times in a single hour, generating enough gas to launch a weather balloon.


Farting is also a source of considerable embarrassment for patients with the Irritable Bowel Syndrome; those with diarrhoea because rapid passage through the gut reduces the absorption of protein and carbohydrate, adding fuel for fermentation; those with constipation because they have a extra large pool of bacteria in the colon, which is fed by the soluble fibre (methylcellulose and isphagula husk) and unabsorbed sugars (lactulose syrup and prebiotics) that are used to treat the symptom. 



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 such material.


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 bananas, apples, pears, reheated potatoes, cereal fibre and Jerusalem artichoke are also very gassy. Unfortunately these foods 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’s the offensive odour is the problem, 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 (  Simethicone (Gas X, Mylicon, Phazyme, Flatulex, Mylanta Gas) reduces the surface tension of gas bubbles in the gut so that small bubbles join to produce big bubbles which are more easily expelled.  Beano is a capsule that contains enzymes 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.


There is even a product called Fartypants, tight underwear containing a fart filter of activated carbon ( They are hardly a fashion statement but they may nevertheless be a useful aid to socialisation.  And now, hot from the factory, is ‘GasBGon’, your own personal cushion containing a gas absorbent (  



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!