Each and every day, Americans collectively fart between 2.5 and 6.3 billion times, unloading up to 466.7 million liters of gas into the atmosphere. Approximately 99% of an "anal gas evacuation" is composed of odorless gases, mostly hydrogen, carbon dioxide, and methane, along with smaller amounts of nitrogen and oxygen. The remaining 1% of compounds grant the fart its notorious scent. Hydrogen sulfide is the chief culprit.
A fart's life begins with food. After entering your mouth and traveling down the esophagus, a meal makes its way to the stomach to be digested and, soon after, the small intestine, where nutrients are absorbed. Some dregs, however, survive the acidic gauntlet and continue to the next leg of the journey: the large intestine. There, what began as a meal for you becomes a feast for resident bacteria. They ferment the leftover food, releasing gas in the process, gas which must be expelled.
Flatulence's omnipresence, smell, sound, and social stigma make it a frequently explored topic in popular culture. Men gathered around restaurant feasts of beer, buffalo wings, and nachos perform much of the experimentation and discussion. Scientists' contributions, while noteworthy, pale in comparison. Sure, they've calculated the average volume of a fart (between 5 and 375 millileters), identified two strains of bacteria to make beans "flatulence-free," and documented the causes of extreme flatulence, but they haven't characterized the magnificence and grandeur of a fart's flammability with anywhere near the precision of the common man equipped with a camera and a YouTube account.
With two new papers, one published in the journal Gut in June 2013, and the other just published to Neurogastroenterology and Motility, Spanish researcher Fernando Azpiroz takes the attention off of fart jokes (at least temporarily) and bolsters our scientific knowledge on passing gas.
Most recently, he tested how two different diets affected flatulence. For the longest time, experts have been recommending foods to reduce gassiness, but surprisingly, there actually hasn't been a study conducted that gauges how eating those foods affects the frequency of farting.
Until now, that is.
Azpiroz assigned a group of 15 subjects to a low-flatulence diet restricted to foods like meat, fish, fowl, eggs; lettuce, tomatoes, avocado, olives; rice, gluten-free bread, rice bread; dairy products; strained orange juice, berries; and sugar, chocolate, coffee, wine, vinegar, oil. He assigned 15 more subjects to a Mediterranean diet of 2-3 portions of meat, fowl, fish, or eggs; two portions of vegetables, salad or legumes; four portions of bread, rice, pasta, potatoes, or cereals; two portions of dairy products; two portions of fruit; and three portions of oil or butter. Subjects consumed their diets for seven days and used a counter to register "every passage of anal gas."
Azpiroz found that the low-flatulence diet reduced subjects' incidents of farting by 54%, while the Mediterranean diet reduced them by 28%. The low-flatulence diet offered a statistically significant improvement over subjects' base diet, but not over the Mediterranean diet. While the result wasn't a completely undisputed victory for so-called low-flatulence foods, Azpiroz noted that they do appear to be beneficial.
"In patients with gas-related symptoms, a low-flatulogenic diet produces immediate beneficial effects with digestive, cognitive, and emotive dimensions," he said. In other words, subjects reported that they felt better.
Last June, Azpiroz teamed up with 15 other doctors and researchers to examine which of the bacteria inhabiting our large intestine, if any, correlate to increased frequency of farting. Bacteroides uniformis, Bacteroides ovatus and Parabacteoides distasonis were indicted, though no causal mechanism has yet been found linking them to the smelly crimes.
Such an examination is likely needed. A cursory Google search on the treatments for flatulence yields a range of recommendations, from diets, to probiotics, to woo. Most lack sufficient scientific substantiation, or any at all. If researchers could pinpoint the gut flora's role in farting, future treatment strategies may be revealed.