The gas we pass

Benjamin Franklin once wrote that “it is universally known that in digesting our common food there is produced in the bowels of human creatures a great quantity of wind.” As escaping gas is offensive because of its smell, and retained gas causes pain and disease, he wished one would discover a drug that “shall render the natural discharges of wind from our bodies, not only inoffensive, but agreeable as perfumes.”

Alas, no such agent has ever been discovered. Coming closest, as we learn from Jim Dawson's 1999 book Who Cut the Cheese: A Cultural History of the Fart (Ten Speed Press), was the Italian courtesan who in the company of her paramours would surreptitiously crush a vial of perfume while simultaneously making an audible sound.

Mr Dawson informs us that less than 1% of the intestinal gas (ammonia, skatole, hydrogen sulfide) is malodorous. The other gases (nitrogen, hydrogen, carbon dioxide, methane, oxygen) are odourless. The gases are produced by E coli and other bacteria fermenting oligosaccharides that originate from milk products, bread, fruits, and vegetables, especially beans. Each day a human generates a litre of gas; an elephant, a thousand litres of methane. Climatic changes have been attributed to emissions from dinosaurs; the greenhouse effect to methane from cows.

Hippocrates, Petronius, Montaigne, and Sir Thomas Moore believed that holding back gas was harmful. In AD 41 the emperor Claudius planned to legitimise passing wind at banquets. In 1975 Dr Wynne Jones proposed that retention of flatus caused diverticular disease and recommended passing flatus at every act of micturition (Lancet 1975;2: 211). He also advised exercise, as did the researchers who pumped air into volunteers and found that pedalling on a bike facilitated gas evacuation and relieved bloating (American Journal of Medicine 2004;116: 536-9).

In his book Mr Dawson classifies emissions into explosive, thunderous, repetitive, and musical. The word itself comes from the Indo-European root “pert.” Said to be more offensive to Protestant than to Catholic ears, it was labelled “not in decent use” in the early Oxford English Dictionary, omitted by Webster's in 1909, but reinstated in 1961. For many it remains what Edward Gibbon would have called “an indelicate subject of conversation.”