Yogurt's probiotics aren't the magical health bullet we think they are

Probiotics aren't actually improving our gut health. Or at least they're not as scientifically sound as yogurt marketers lead us to believe. 

Ed Yong, author of I Contain Multitudes, a new book about gut microbiota, tells Terry Gross of Fresh Air that store-bought probiotics aren't very good at populating our guts with helpful bacteria, and yogurt isn't much better. 

"I think of them as, like, a breeze that blows between two open windows," Yong told Gross. "It might rattle a couple of objects in the way, but it doesn't have a lasting impact." 

Jamie Lee Curtis was lying to us in those Activia yogurt commercials. In fact, there was a $35 million class-action lawsuit against the company for false advertising in 2009: Clinical studies did not support Activia's claim that the yogurts can regulate digestion in two weeks, the Canadian Society of Intestinal Research noted. 

Probiotics are having a moment — but the hype exceeds the science. Stroll through a grocery aisle and you'll see yogurts, protein bars, kombucha and baking mixes adorned with labels bragging about probiotic content. But the evidence in favor of the allegedly good-for-you bacteria is complicated. There are tons of different strains of probiotics, and studies often investigate blends of strains, meaning it's hard to isolate cause and effect for a single strain, FiveThirtyEight reported. 

Yong noted that some strains of probiotics are chosen for food products because they're easy to manufacture, not because they are necessarily better at aiding gut health. 

Luckily, there's salvation for those with a gut starved of good bacteria. Yong noted that fecal transplants are one of the best microbiome treatments right now. It's "spectacularly effective" at treating reoccurring severe diarrhea. 

Who knew poop problems could be cured with more poop? Sounds crappy, but it allegedly makes tummies (and toilets) happy. 

August 19, 2:25 p.m.: This story has been updated.