“Fecal microbial transplants” treat someone’s unhealthy gut with poop from someone else’s healthy gut, and proponents of FMT claim it can help treat everything from IBS to autism. But if your doctor isn’t ready to fill you up with someone else’s poop, the internet will happily oblige.  Guest:  Luke Winkie, Slate staff writer who published “The Poop Broker.” Want more What Next TBD? Subscribe to Slate Plus to access ad-free listening to the whole What Next family and all your favorite Slate podcasts. Subscribe today on Apple Podcasts by clicking “Try Free” at the top of our show page. Sign up now at slate.com/whatnextplus to get access wherever you listen. Learn more about your ad choices. Visit megaphone.fm/adchoices