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Lay off the laxatives — even a short bout of diarrhea can ruin your gut microbes’ month

In each of our abdomens sit trillions of microbes, but a bout of diarrhea can induce a lasting round of gut-bug disruption, new research indicates.

A couple of years ago, I wrote an article called "Gut Bust" for our magazine, Stanford Medicine, about the prospect that our modern, civilized lifestyle might be destroying an environment we don't always think about: the one in each of our abdomens, in which sit trillions of microbes representing strains that have coexisted with us for eons.

The benefits of industrial civilization are too numerous to name, I wrote in that article:

Here are just a few: Abundant food supplies. Clean water. Indoor plumbing. Centralized heating. Refrigeration. Public sanitation. Vaccination. Antibiotics. An understanding of the value of hygienic practices such as washing hands and brushing teeth.

All of these, let's face it, miraculous advances have contributed to a potential evolutionary ambush: We have succeeded in decimating our internal microbial ecosystems, which supply all kinds of services in exchange for the abundant nutrients we furnish these resident lifeforms when we eat but then only partially digest all kinds of food, leaving the microbes with the happy job of sucking up much of what's left. This they do with aplomb, often to our mutual benefit because lots of byproducts of that bacterial binge-eating are items we can use but can't make on our own. Like loyal watchdogs, our microbial gut bugs also jealously guard our intestinal turf against invading pathogens.

The accumulation of intestinal-microbe deficits induced by our advanced Western lifestyle (in contrast to the one adhered to by the globe's dwindling remnant populations of active hunter-gatherers) places our ability to transmit healthy resident gut-microbial ecosystems to our offspring in peril.

One thing I didn't allude to in my lengthy laundry list of curses modernity has visited upon our gut-microbial colleagues: intentionally induced diarrhea.

I hadn't realized this was a common phenomenon. But this was brought to my attention with the recent publication of a new study in Cell, spearheaded by Stanford gut spelunker Justin Sonnenburg, PhD, and his bacteria-appraising colleague KC Huang, PhD. They and their fellow researchers showed that even a short bout of diarrhea can induce relatively lasting changes in the composition of the intestinal ecosystem, most likely to our detriment.

Of course, diarrhea is not exactly a new evolutionary phenomenon. What's new is that it's so often triggered deliberately. Over-the-counter laxatives are prevalent in the industrialized world, the Cell study's authors note:

Miralax [a commercial laxative] ... is the second-leading digestive remedy in the United States. ... [L]axitives are frequently abused by people with eating disorders; a reported 10-60 percent of patients with anorexia or bulimia nervosa use laxatives as a method of weight control, leading to chronic diarrhea.

A word to the wise: Lay off the laxatives, barring medical necessity. Killing off our intestinal ecosystems is easier than you might think. We're already too close for comfort.

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