Do you want to know “a few facts about feces”? Or “how does pooping work”? (And who doesn’t?) If so you’ve come to the right place. Giulia Enders, who is working on her medical doctorate, somehow became fascinated with these questions and many more involving our digestive system. The result is this book which won the 2014 Science Slam prize in Berlin and became an international bestseller.
We think of termites and ruminants as having most of their digestion done for them by microbes. But after reading this captivating book it is apparent that we are also totally dependent on our own microbes for digestion. Enders goes so far as to say that “Some scientists now support the theory that our gut microbiota can be considered an organ.” (p. 195)
One of the most interesting and charming aspects of this book and part of the reason for its success is the collaborative translation by David Shaw and Giulia Enders herself that owes so much to Enders’ use of idiom and metaphor, both English and German (sometimes in cute mixed translation). Enders, whose English is more than fluent (listen to her on YouTube) has an impish quality to her expression that adds enormously to the fun of reading this book.
Perhaps the central idea in the book is that the gut itself has a brain that rivals the one on top of our heads. So the old adage that the brain is the stomach’s slave may be more than just a witticism.
Another interesting idea comes in the later chapters dealing with the effects that gut bacteria have on our behavior. Yes, behavior. According to Enders, gut bacteria can send molecular signals to the brain that influence our choice of what foods we eat. Some bacteria want us to eat carbs that they like or foods that are not completely digested until they reach the large intestine where most of our gut bacteria live. Additionally gut bacteria can help us digest well or not so well thereby allowing some people to gain weight on the same diet that other people with different gut bacteria would not gain weight.
Enders speaks of our “microbial signature” noting that “Everyone has some outlandish items in their collection that almost no one else will share.” (p. 172) This made me think: maybe these microbial signatures could someday replace fingerprints or iris recognition for identification. Forensically speaking such signatures might be valuable in some cases.
Still another idea is that there is some evidence that some bacteria can lower cholesterol levels. (p. 193)
It’s obvious that Enders had a lot of fun reading the scientific literature. Take this bit about Toxoplasmata gondii, tiny one-cell organisms that inhabit the guts of cats. (p. 210) Apparently when these organisms get into the digestive system of rats or the rats smell cat urine they cause the rats to seek the company of cats since cats are the definitive hosts for toxoplasmata thereby endangering their little rat lives!
Enders dubs this a “feed myself to the cat instinct.” (p. 213) But could it work with larger mammals? Apparently yes. She writes, “The risk of being involved in a traffic accident is higher among toxoplasma carriers, especially when the infection is in the active stage…” (p. 214)
Even more fantastic is her analysis suggesting that our immune system produces an enzyme (IDO) to protect us from parasites like toxoplasma, and in doing so produces serotonin. Since serotonin makes us feel better (or more precisely, lack of serotonin makes us feel lethargic) toxoplasma can make us feel better. Toxoplasma can even affect the amygdala making us fearless. (See pages 214-215.) Enders mentions “a thirty-two-year-old woman” who cuts her wrists with a razor blade for the thrill of it. (p. 210) Enders concludes this wonderment with these words which are characteristic of her most interesting metaphorical style: “How can pain have become the hot sauce in the otherwise bland soup of her everyday life?” (p. 214)
And here’s a very telling, sad story: some “South Americans” took themselves to the South Pole to have their babies. “The plan was that the babies born there could stake a claim to any oil future reserves as natives of the region. The babies did not survive…The South Pole is so cold and germ-free that the infants simply did not get the bacteria they needed to survive.” (p. 240)
There are many references to the journal articles Enders has read but I wish she had provided endnotes so that we could pair the findings in the text with the confirming studies. For example exactly who did the study that showed that people identified as toxoplasma carriers were involved in more traffic accidents that those not carrying the organism?
Finally I want to say something about the line drawings in the book done by Giulia’s sister, Jill Enders: weird, but oddly amusing. I got a kick out of the one on the final page in which something, perhaps a gut bacterium, is mooning us.
--Dennis Littrell, author of “The World Is Not as We Think It Is”
Gut: The Inside Story of Our Body's Most Underrated Organ
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Last update: 05-10-2024
Top reviews from the United States
Dennis Littrell
Gut science explained with charm and candor
Reviewed in the United States on October 14, 2016
Molly
Lively writing and fun facts, not all of them true
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