So—if you assume as I did that Mary Roach’s Gulp will be straight narration down the alimentary canal (into the mouth, down the throat, into the stomach, into the intestines and beyond)—you’re going to be more than surprised by the book’s structure. Not strictly an in/out affair. “Adventures” from the sub-title is the most accurate description of Roach’s “story,” though that’s not exactly the right word. So let’s start again.
Mary Roach (who has been described as “America’s funniest science writer” [in part because of her earlier work, Stiff, about corpses]) carefully sets her own boundaries at the end of her introduction, “You will occasionally not believe me, but my aim is not to disgust…. I don’t want you to say, ‘This is gross.’ I want you to say, ‘I thought this would be gross, but it’s really interesting.’ Okay, and maybe a little gross.” But, I’d say, ALWAYS interesting.
After the introduction, Roach begins with the nose, with a very revealing title (“Nose Job”) and sub-title (“Tasting Has Little to Do with Taste”) for her first chapter. Most of what we taste is because of what we smell. “Eighty to ninety percent of the sensory experience of eating is olfaction.” Which “is why dogs stick their heads out of the car window.” Not to feel the wind but to catch the smells. That fact may not be a surprise to many people because we’ve all learned how sensitive dogs’ noses are. But this is why “I’ll Have the Putrescine,” the second chapter, dwells on the manufacturing of dog food that will attract canines but not give them what they really want—smells so offensive that their owners will not buy the product. It’s a fascinating chapter about a huge business (including cat food) in the United States. Getting the smell of dog food (mostly coverings of various grains) right is a tricky business because “the average dog’s nose is about a thousand times more sensitive than the average human’s.”
Roach’s discussion of the mouth is mostly about food, and what we eat is largely determined by culture. Probably availability or lack of availability also. I do remember a guide in Vietnam telling me that anything that flys, crawls, walks, or swims is fair game, i.e., everything, so I decided that I would taste dung beetles. I also remember catching locusts the last year they invaded our yard and sautéing them for a delicious, crunchy appetizer. Even our children ate eat them, as they’ve been eaten around the world for their protein.
But I digress. Roach is equally fascinated by mastication and its various fads down through the years. Consider Horace Fletcher, the formulator of “Fletcherizing.” What’s that? Well, we’ve all been told not to eat too quickly, to chew our food. Horace concluded that 722 (not 721 or 723, but 722) mastications were necessary before swallowing, “by chewing each mouthful of food until it liquefies, the eater could absorb more or less double the amount of vitamins and other nutrients.” The plan was economic, sounding like some Tea Party gimmick to balance the budget, because if double the amount of necessary nutrients were absorbed, think how much less food would need to be conserved.
In 1901, Horace wrote in a letter that “Half the food commonly consumed is sufficient for man.” Too many people, including scientists, took him seriously. Various institutions and government agencies were interested. Consider how much money could be saved feeding the poor. (Half the number of food stamps?) There was just one major problem. A modest meal would take half the day to masticate. Who had time for that? Who has the time for most dimwit ideas that temporarily electrify the public?
Much of what we know about what happens to food in the stomach is the result of one doctor (William Beaumont) and his patient, Alexis St. Martin. In 1822, St. Martin (a Canadian trapper) was shot in the stomach, and the puncture left a “protruding portion large enough” to accommodate a finger and—more importantly—an observation opening into the activities within. Dr. Beaumont realized the extraordinary window of opportunity the hole provided, making it possible to insert and remove various objects in order to observe what happened to them as they were digested. Experiments were undertaken in the man for years, decades. Beaumont eventually published his observations in Experiments and Observations on the Gastric Juice, and the Physiology of Digestion, but (no surprise) the book did not become a best-seller.
Moving on to saliva, Roach informs us that the average human being produces two to three pints each day. Saliva so effectively begins the breakdown of food particles that laundry detergent has evolved so that it uses some of the same enzymes. “Laundry detergent is essentially a digestive tract in a box.” Saliva is also healthy. Dogs lick their wounds in order to heal them with the saliva. “Human saliva contains histatins, which not only kill bacteria but also speed wound closure….”
If the stomach juices are so strong, why doesn’t the stomach digest itself? The stomach “swiftly rebuilds what it breaks down. A healthy adult has a new stomach lining every three days.” In a side note, Roach observes that “Penguins can shut down digestion by lowering the temperature inside their stomach to the point where the gastric juices are no longer active. The stomach becomes a kind of cooler to carry home the fish they’ve caught for their young.” That remark comes in the text of Roach’s book but some of her most revealing—and hilarious—observations are left for its numerous footnotes. This is one book where you do not want to skip those footnotes.
Or an observation about over-eating such as this one:
“…a pair of Dade County medical examiners reported the case of a thirty-one-year-old bulimic psychologist found seminude and fully dead on her kitchen floor, her abdomen greatly distended by two-plus gallons of poorly chewed hot dogs, broccoli, and breakfast cereal. The MEs found the body slumped against a cabinet, ‘surrounded by an abundance of various foodstuffs, broken soft drink bottles, a can opener and an empty grocery bag’ and—‘the coup de grace’—a partially empty box of baking soda, the poor man’s Alka-Seltzer. In this case, the greatly ballooned stomach had not burst; rather, it killed her by shoving her diaphragm up into her lungs and asphyxiating her. The pair theorized that the gas could have forced one of the poorly chewed hotdogs up against the esophageal sphincter, at the top of the stomach, and held it there, preventing the woman from burping and vomiting.”
So, yes, you can die of over-eating. Chew your food properly. Maybe not 722 times.
Moving further south, Roach talks about the dangers of rectal transporting, i.e., “the alimentary canal as criminal accomplice,” with incredible lists of objects that have been hidden therein, though some people insert things there simply for kinks. I mean kicks. Then she discusses the inflammable gases that may do a number on you, though this is not very common and perhaps not necessary to put at the top your list. There are scientists who have devoted their careers to studying flatulence. Let them worry for you. Roach further opines about scientists who have speculated that eating feces may have some nutritional value, since what has been definitely proven is that both mice and rabbits eat their first droppings because they contain “nutrients that are synthesized in the lower intestine” and necessary for their growth. Without them, they would be stunted.
In case you are still reading this (and more importantly intending to read Gulp), the concluding chapters deal with constipation and some revealing facts about Elvis Presley’s colon and, finally, the current cutting-edge experiments going on in the colectrical community with fecal transplants (as a cure for c. diff). And Roach’s conclusion, because it’s not drawn solely on fecal matter: “I predict that one way or another, within a decade, everyone will know someone who’s benefited from a dose of someone else’s body products.” Which adds new meaning to “neither a borrower nor a debtor be.”
I haven’t had so much fun reading a book in years as Gulp. There’s actually a zinger on almost every page. So read Mary Roach’s hilarious commentary on why we are what we process.
Mary Roach: Gulp: Adventures on the Alimentary Canal
W. W. Norton, 336 pp., $26.95
Charles R. Larson is Emeritus Professor of Literature at American University in Washington, D.C. Email: firstname.lastname@example.org.