MANNHEIM, Germany — IF Giulia Enders had not contracted a mysterious illness as a teenager that left her covered with sores, she, like most of us, might never have thought much about her digestive tract, except when it was out of whack. She might never have enrolled in medical school, either, and she almost certainly would not have written a best-selling book about digestion last year that has captivated Germany, a nation viewed, fairly or not, as exceedingly anal-retentive.
Back in 2007, after a series of mostly ineffective treatments prescribed by doctors, Ms. Enders, then 17, decided to take matters into her own hands. Convinced that the illness was somehow associated with her intestines, she pored over gastroenterological research, consumed probiotic bacterial cultures meant to aid digestion and tried out mineral supplements.
The experiments worked (although she is not sure which one did the trick), leaving her with healthy skin and a newfound interest in her intestines. “I experienced with my own body that knowledge is power,” she writes of the episode in “Gut: The Inside Story of Our Body’s Most Underrated Organ,” which was published in North America last month after its surprising success in Germany, where it has sold almost 1.5 million copies since its release in March 2014.
Inspired by her successful self-experimentation, Ms. Enders enrolled in medical school in 2009 at Goethe University Frankfurt and is now working toward a doctoral degree in microbiology there.
DURING a recent interview in a cafe here next to the Neckar River, not far from her childhood home, Ms. Enders, now 25, sipped chamomile tea and described with characteristic enthusiasm the first stomach operation she saw in person. “The whole body moves like this or like that, but the intestines move in entirely a different way,” she said. “It’s incredibly harmonious!”
Ms. Enders’s wonder at the strange ways of the gut is matched only by her incredulity at the limited public knowledge on the subject. “I’m almost shocked,” she recalled thinking during her first years in medical school as she learned, for example, that it is easier to burp lying on your left side than your right because of the position at which the esophagus connects to the stomach. “Why doesn’t everybody know this?”
In 2012, she began taking it upon herself to fill people in. She had heard about a student event space in Freiburg that was hosting a “science slam,” an open-mike event where young researchers give presentations, and decided to prepare a short lecture on digestion.
Onstage, Ms. Enders was bouncy and jocular, as a video of the event shows. She speaks rapidly, hardly able to contain her excitement, describing the components of the digestive system and lamenting its poor reputation.
“It’s really too bad, because the intestines are totally charming,” she says, citing as evidence the sophisticated communication between our inner and outer sphincter muscles and the some hundred trillion bacteria in our guts that facilitate digestion.
The crowd was smitten. Ms. Enders won the competition and went on to participate in two more science slams in Karlsruhe and Berlin. Soon, videos of her presentations were attracting attention online, and a literary agent contacted her about writing a book.
FANS have praised Ms. Enders for translating abstruse gastroenterological research into breezy, entertaining prose. On a talk show here last April, she described the large intestine as the “chiller” of the two because it processes nutrients at a leisurely pace of about 16 hours on average, compared with the two to five hours that the small intestine needs.
In her book, she catalogs the myriad elaborate operations that our guts dutifully perform every day, like the cleaning mechanism that kicks in a few hours after we eat and keeps the small intestine — all 20 or so feet of it — remarkably tidy. This “little housekeeper,” as Ms. Enders calls it, turns out to be the real source of the grumbling that most attribute to the stomach and mistake as a sign of hunger.
Then there is the growing body of research indicating that our intestines may have a far greater influence on our feelings, decisions and behavior than previously realized. The primary evidence for this, Ms. Enders writes, is the vast network of nerves attached to our guts that monitors our deepest internal experiences and sends information to the brain, including to those regions responsible for self-awareness, memory and even morality.
Just how much your lunch will affect ethical decision making remains unclear; we still know very little about this “gut brain,” as Ms. Enders refers to it. But this byzantine neural architecture suggests that our intestines may play a large part in determining who we are and what we do.
These essential but little-known features of our guts — our identities at their most raw and visceral, Ms. Enders suggests — have riveted Germans. The surprising popularity of Ms. Enders’s book has itself become a topic for discussion, with some commentators invoking Freud to explain Germans’ apparent fascination with their bowels. Profanity here tends to skew to the scatological, and Germans are, according to stereotypes, obsessed with order and neatness.
Ms. Enders dismisses such talk, noting that the book has also topped best-seller lists in Finland, the Netherlands and elsewhere. She suggests that its appeal lies in its frank treatment of topics usually left undiscussed. “Shame always disappears when you really understand something,” she said.
MS. ENDERS grew up on the outskirts of Mannheim, a sleepy city of almost 300,000 residents that was largely flattened by Allied bombs in World War II and filled back in with prim, modern buildings. Her parents split up when she was young, and her father was an irregular presence during her childhood. “You can only say Lebenskünstler,” she said to describe him — a term that means “life artist” and connotes a bohemian disregard for societal conventions.
Instead, it was her mother, a former documentary filmmaker, and grandmother who raised Ms. Enders and her older sister, now a graphic designer based in Karlsruhe who contributed illustrations to the book. Her grandmother, an interpreter by training, proved particularly influential. “She showed us very early on that intellectuality doesn’t have to be so serious,” said Ms. Enders, who recalled free-form games of chess with her grandmother in which they ignored half of the rules.
But Ms. Enders’s interest in science is relatively new. She was, by her own assessment, a mediocre student in elementary school, owing mostly to self-described boredom with the rote exercises in primary education. While her grades improved in high school, her fascination with medicine began outside the classroom, with the unexplained sores she had as a teenager.
By her own account, Ms. Enders’s sudden fame has not changed her life very much. She still shares the same apartment in Frankfurt with five friends. She recently completed a state medical exam and will soon begin a yearlong residency at a hospital.
She does not have any immediate plans to write another book. “If I have that feeling again,” she said, referring to her surprise at how little most people knew about digestion, “then I’d do it. But only then. And if that feeling doesn’t come, then hopefully I’ll just be a good doctor.”