Mary Roach - Gulp

Whereupon Kligerman frowned. Earlier, when Len tried to tell a story that began, “There was a guy on my floor freshman year…,” Kligerman threw this particular bucket of cold water: “This is not a humorous subject.”

When Kligerman got up to take a phone call, I scooted my chair over to Betty Corson’s side. I wanted to know who’d been calling the Beano Hotline lately. She told me about a woman whose boyfriend kept pulling over to “check the air in the tires.” More typically, it is women, mostly of my mother’s generation, who don’t want anyone, ever, under any circumstances, to hear them. Like the gassy nun at the Holy Spirit–Corpus Christi Monastery, who had called earlier in the day. “She talked very quietly,” said Corson.

Why not just avoid legumes? Some people can’t, said Corson. I challenged her to provide a single instance of a human being forced to eat beans. She came back with “refried-bean tasters.” They exist and they have called the hotline. “Can you imagine?” She slapped the table. “Honest to God.” With Kligerman gone from the table, the conversation had loosened its tie a little.

I know one other example of beans eaten against one’s will. Inmates in solitary confinement in state prisons are sometimes fed a single, nutritiously complete but wholly unappetizing food called Nutraloaf. (Often these are convicts who’ve attacked someone with their silverware. Nutraloaf is an entire meal you can pick up and eat by hand.) Beans are invariably a main ingredient, as are bread crumbs, whole wheat flour, and cabbage: major gas generators all. Inmates in several states have sued on the grounds that Nutraloaf three times a day constitutes cruel and unusual punishment. In the article I read, taste was the issue, but an elderly convict could probably build a case out of gas pain.

When Kligerman returned, he was carrying what looked like a potato chip bag with a snorkel apparatus at one end. He explained that he needed to get a baseline reading before I ate my beans. He handed the device to me. “When you do your blows—”

It was unlike Kligerman to employ slang in reference to flatus. It quickly became clear that the snorkelly thing, like any snorkelly thing, went in the mouth, not the rectum. I was both relieved and disappointed: he was doing a breath hydrogen test. If you know the amount of hydrogen someone is exhaling orally, it’s a simple matter to extrapolate the amount they’re exhaling rectally. This is because a fixed percentage of the hydrogen produced in the colon is absorbed into the blood and, when it reaches the lungs, exhaled. The breath hydrogen test has given flatus researchers a simple, consistent measure of gas production that does not require the subject to fart into a balloon.

Up through the 1970s, however, that’s how it was done. A retired bean scientist told me the story of a flatus research project carried out by the extremely appropriately named Colin Leakey, at a food science facility in Chipping Campden, near Stratford-upon-Avon. If I’d been a tourist passing through, I might have skipped the Shakespeare and gone over to Chipping Campden to have a peek. “People walked around in gowns”—hospital, presumably, not ballroom—“with a tube coming down and around and up into a balloon.” Stateside, in 1941, J. M. Beazell and A. C. Ivy rigged up something similar: “The gas was collected in a thick-walled rubber balloon by means of a 22 French colon tube which was inserted into the rectum about 10 cm [4 inches]. In order to hold the tube in place, a broad strip of dental rubber dam was attached to it at the point where it emerged from the rectum and this was brought up snugly along the gluteal fold and fixed to the abdomen and back by means of adhesive tape. With this arrangement the subjects were able to remain ambulatory with surprisingly little discomfort.”

The researchers were fooling themselves, says Michael Levitt. “The rectal tube is… uncomfortable, tends to plug, and cannot be used for prolonged periods in free-living subjects,” he wrote in a 1996 paper. For studies of gas volume, he preferred the “flatographic recording” technique, wherein the subjects would make a notation in a special diary of each “passage.” The method isn’t entirely dependable, however, because different people’s passages may contain widely varying amounts of gas, depending on whether… how shall I put this? On whether they are my husband or my mother-in-law. On whether they expel it with gusto or try to hold it in, letting it out in many tiny squeakers and falsely upping their flatographic tally.

Len pointed out a related shortcoming to the breath hydrogen test. When people, stereotypically women, hold in their gas, they absorb more of it into their bloodstream, “so it comes out in the breath.” This artificially raises their breath hydrogen numbers and may serve to explain the occasional highly counterintuitive finding that women are more flatulent than men.

“Right, Alan?”

Kligerman stirred his chili. “I don’t know, Len. I don’t know what the ultimate fate of a suppressed fart is.”

RECTAL TUBES AND breath hydrogen bags have their drawbacks, but either is an improvement on the original methodology. One of the earliest flatus studies on record was carried out by the Parisian physician François Magendie. In 1816, Magendie published a paper entitled “Note on the Intestinal Gas of a Healthy Man.” The title is misleading, for although the man in question suffered no illness, he was dead and missing his head. “In Paris,” Magendie wrote in Annales de Chimie et de Physique , “the condemned ordinarily, one hour or two before their execution, have a light meal.” With red wine. So French! “Digestion is thus fully active at the moment of their death.” From 1814 to 1815, the city fathers of Paris, seeming also to have lost their heads, agreed to release the bodies of four guillotined men to Magendie’s lab for a study on the chemical makeup of flatus. One to four hours after the blade had dropped, Magendie extracted gas from four points along the digestive tract and measured what he could.

One of the prisoners Magendie “opened” had consumed lentils as part of his last meal. I would have expected this man to have had the highest hydrogen level—legumes, as we just learned, being the largest supplier of unabsorbed carbohydrates to hungry colon bacteria. Oddly, the highest hydrogen level came out of the prisoner who had eaten “ pain de prison et du fromage de Gruyère. ” Gruyère cheese and “prison bread.” Were Paris jailers serving some sort of early French precursor to Nutraloaf? Probably not. For many people, unabsorbed carbohydrates from wheat are a sizable contributor to gas. And if you’re going to be dead in two hours, there’s no reason not to fill up on bread.

What amazed me about Magendie, aside from his zest for gore, was this: using instruments available in 1814, he was able to detect hydrogen sulfide, a gas that typically makes up one-ten-thousandth of the gas produced in the human colon. It’s possible the instrument Magendie used was, in fact, his nose. The human olfactory system detects the rotten-egg smell of hydrogen sulfide at the practically nonexistent rate of .02 parts per million. Though present in no more than trace amounts, hydrogen sulfide is, in the words of Michael Levitt, “the most important determinant of flatus odor.” He would know.

MICHAEL LEVITT DID not set out to make his mark on the world by parsing the secrets of noxious flatus. His fellowship advisor had the idea. The gas chromatograph had just come into use as a laboratory tool, and no one had yet had the ingenuity—or nerve—to apply the technology to human emissions. “He called me into his office,” Levitt recalls. “He said, ‘I think you ought to study gas.’ I said, ‘Why’s that?’ He said, ‘Because you’re pretty much of an incompetent, and this way if you discover anything, at least it’ll be new, and you’ll be able to publish something.’”