Could Running Change Your Brain?

Running an entire marathon takes a lot of energy. Neuroscientist Carlos Matute https://www.neurobiologylab.org/people/carlos-matute knows this: he's run 18 of them. He wondered how runners' bodies get the energy they need to make it to the finish line. His new research in the journal Nature Metabolism https://www.nature.com/articles/s42255-025-01244-7 may be the first step in answering the question – and suggests their brains might be (temporarily) depleting a fatty substance that coats nerve cells called myelin. Have other questions about the brain? Let us know by emailing [email protected] mailto:[email protected]! Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave http://plus.npr.org/shortwave. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

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• 0:16Speaker 01

  You're listening to Short Wave from NPR.

• 0:21Regina Barber?

  Hey, Short Wavers. Regina Barber here.

• 0:23Speaker 01

  And Rachel Carlson.

• 0:24Regina Barber?

  With our biweekly science news roundup, featuring Juana Summers, of all things considered. Hey, Juana.

• 0:29Speaker 01

  Hi, excited to be here. I hear we're talking about one of my favorite things, running, and how running a marathon can change your brain.

• 0:35Regina Barber?

  Yep. Plus, we're talking about fermenting food in space and what it does to its taste.

• 0:40Speaker 01

  And scientists have solved a longstanding mystery of how hordes of bats emerging from caves avoid bat-on-bat collisions.

• 0:47Regina Barber?

  I'm intrigued, y'all. All of that on this episode of Short Wave, the science podcast from NPR.

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• 2:25Speaker 04

  All right, just to start off, tell me about marathon running. I'm training for one myself, so I'm really interested in this story.

• 2:30Speaker 01

  Yeah, OK, so especially if you're training for a marathon, I think we can both imagine that running one would take a lot of energy.

• 2:37Speaker 04

  Yes.

• 2:37Speaker 01

  Neuroscientist Carlos Matute told me he's done 18 marathons, so he really knows it's exhausting. And he told me that he wondered, how do runners' bodies get the energy they need to make it to the finish line? His new research in the journal Nature Metabolism suggests their brains might be depleting a fatty substance called myelin.

• 2:56Speaker 04

  So it's sort of like your brain is eating itself when it's running low on energy?

• 3:00Speaker 01

  Yeah, that's kind of how I was thinking about it. Myelin coats nerve cells and helps electrical signals travel, and it makes up about 40% of the brain.

• 3:08Regina Barber?

  And after marathons, they saw that myelin decreased in the runners' brains, especially in the areas of the brain that are important for things like motor coordination, like how we move our bodies, and sensory processing.

• 3:18Speaker 04

  So after a marathon, there's less myelin. Is that a bad thing?

• 3:22Speaker 01

  Well, the changes were all temporary. The researchers followed up with the runners two months after the marathon and scanned their brains again. And they saw that the amount of myelin returned to normal.

• 3:30Regina Barber?

  But there are some neurological diseases where myelin decreases and doesn't return to normal. Carlos thinks studying runners could help us better understand these disorders, like multiple sclerosis.

• 3:40Speaker 05

  It may be useful to develop new lines of treatment for multiple sclerosis, for slowing aging, and perhaps neurodegenerative diseases.

• 3:53Speaker 04

  Like neurodegenerative diseases. OK, so for marathon runners, or marathon runner hopefuls like me, it sounds like we're all OK to keep on running.

• 4:01Speaker 01

  Yeah, and the study has a few limitations. One of them is that they only looked at 10 runners' brains, so it was a very small sample size.

• 4:08Regina Barber?

  Another neuroscientist in the field, Yanik Poitelot, told us the kind of scans the researchers took makes it hard to say for sure that running caused the change in myelin. But he says that this study was really exciting. It's one of the first to show that human myelin could be used as an energy source. And he thinks it could inspire lots of new work in the field.

• 4:25Speaker 04

  All right. So next up, we've got fermenting food in space. I'm always good for food stories. So what kind of food are we talking about here?

• 4:32Regina Barber?

  Yeah, it was miso.

• 4:33Speaker 04

  Yum.

• 4:33Regina Barber?

  The paste created from like fermented soybeans or grains. It's used a lot in Japanese cooking. And part of this study is in service of astronaut nutrition. Like, how do we make their diets more delicious, more nutritious, more diverse?

• 4:44Speaker 01

  And the researchers were also wondering, how does this specific space environment, the space station, shape microbial life in unique ways? And understanding that's important for any kind of space travel.

• 4:54Speaker 04

  So how did this miso make its way into space?

• 4:56Regina Barber?

  Well, Wana, it almost didn't. I spoke to Maggie Koblenz and Josh Evans, who published their study in the journal I Science This Week. And Josh reminded me that like most fermented things have a really strong smell. And this fact almost stopped them from getting the experiment into space.

• 5:10Speaker 06

  The miso was ready to be put into the shuttle in Houston. And then we got this kind of, or Maggie got this frantic call from someone from NASA, being like, um, your payload is like kind of smelling weird.

• 5:21Regina Barber?

  But fortunately, once NASA like got the explanation, they launched it anyway.

• 5:25Speaker 04

  So what did the researchers learn from this fermenting adventure?

• 5:28Speaker 01

  Well, Maggie's big takeaway is that it worked.

• 5:30Speaker 07

  Fermentation is possible in the International Space Station.

• 5:34Speaker 01

  So if this worked, who knows what astronauts could get into next when fermenting stuff in space? Maybe sourdough, kimchi. I guess there's also stinky cheese, but I feel like if I were an astronaut, I'd be a little worried about that one. Personal choice, though.

• 5:48Speaker 04

  I mean, as a cook, or an attempted cook, I'm sort of curious. Did fermenting this miso in space make it taste any different than making it on Earth?

• 5:56Regina Barber?

  Yeah, it did. When it came back to Earth, it tasted nuttier than the miso from the same batch like fermented on the ground.

• 6:02Speaker 04

  Interesting. Why do they think that happened?

• 6:04Regina Barber?

  So they don't know for sure. It could have been like radiation. It could be microgravity. It could be a combination of all of this. But the leading hypothesis is that it was mostly temperature swings inside the space station.

• 6:14Speaker 04

  All right, y'all, let's bring it home. We've got to end on bats. You say that scientists figured out how they avoid collisions?

• 6:20Regina Barber?

  Yeah. So this was a big mystery that perplexed researchers for a while. Like, basically, bats emerge from their caves like around dusk all at once. There can be hundreds, thousands, or even millions of bats in a group, all funneling out together. And for the most part, they don't crash into each other.

• 6:35Speaker 01

  And just a reminder, bats navigate using sound. It's called echolocation. They send out a vocalization, a call, and then they listen for its echo off objects in their path. But when a million bats are all flying out of a cave together, that's a lot of bat calls that could get mixed up. Here, let's take a listen.

• 6:55Speaker 04

  Oh my gosh.

• 6:56Regina Barber?

  Wow, that's incredible. So how did scientists sort of sort out all of these different calls? Yeah, lead researcher Aya Goldstein said one big innovation was tiny microphones. We can put microphone on bats. We can track many individuals at the same time. Aya says scientists used to put microphones in front of the caves to measure the sounds of bats emerging, or they would have like a few bats in captivity. But none of this really got to an individual bat's perspective while in a densely packed group.

• 7:24Speaker 04

  Maybe we need to let them borrow an NPR producer to mic up their bats next time.

• 7:28Regina Barber?

  Yes, yes. Aya did this work while at Tel Aviv University in Israel. She and her team also used some new tracking technology using these little tags they put on bats to monitor their location. And when they combined acoustic data from these personal bat microphones, they figured out how a bat changed its call based on the density of bats around them, which they reported on in the proceedings of the National Academy of Sciences this week.

• 7:52Speaker 04

  Well, you've got to tell me, how do they change their calls?

• 7:54Regina Barber?

  So they found that when the bats were like very densely packed, their calls were shorter, higher pitched, lower in volume, and more frequent. And all of this essentially allows a bat to hear its own call echoed back instead of disappearing in like the ruckus of other bat sounds. Bat behavioral ecologist Rachel Page at the Smithsonian Tropical Research Institute in Panama, who wasn't involved in this work, said that this was a major advance in the field. I think this is giving us insight that that really is unparalleled, like that

• 8:21Speaker 04

  you cannot get when you bring bats into a lab. Well, y'all, any lessons from this bat mystery that could help us humans?

• 8:28Regina Barber?

  Yeah, Aya says that understanding how bats navigate could help engineers design flying robots that could swarm, which might be helpful in agriculture or environmental sensing.

• 8:37Speaker 04

  Ooh, super interesting. That is something I would have never thought about.

• 8:40Regina Barber?

  Thanks for joining us, Wana. Yeah, thank you.

• 8:43Speaker 04

  Thanks for letting me come back.

• 8:44Regina Barber?

  You can hear more of Wana Summers on Consider This, NPR's afternoon podcast about what the news means for you. This episode was produced by Burleigh McCoy and Mia Venkat. It was edited by Jeff Brumfield and Christopher Ntolyanta. Tyler Jones checked the facts. Kwasi Lee and Jimmy Keely were the audio engineers. I'm Rachel Carlson.

• 9:01Speaker 04

  And I'm Regina Barber.

• 9:03Regina Barber?

  Thank you for listening to Short Wave, the science podcast from NPR.

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