I think most people would assume that running is good for your body. After all, exercise is good, and given that running is free (if you can afford a good pair of shoes), it’s what many people turn to when they want to get into shape.

Now scientists say they’ve found some evidence that running long distances might physically impact your brain.

Or at least, your brain.

This study has not been peer-reviewed yet, but is claiming that the bodies of marathon runners could use brain tissue as a way to refuel mid-race.

Specifically, that it would devour the myelin layer of fatty tissue that coats our brain and nerve fibers.

Until now, these myelin layers – or sheaths – have been thought to be “inert structures of insulation that don’t change much after they’re made.”

This paper claims the opposite. They say that marathoner brain scans reveal it to be a dynamic and adaptable tissue that can and is used as a replenishable source of fuel.

Carlos Matute, a neurobiologist at the Achucarro Basque Center for Neuroscience, headed the study. It included taking images of four marathon runners’ brains immediately before and after a big race.

The scans taken afterward show stark declines in the myelin sheath, which seemed to support their hypothesis that their bodies cannibalized it in order to finish the race.

A neuroimaging scientist who was not involved weighed in on the potential finding.

“This is definitely an intriguing observation. It is quite plausible that myelin lipids are used as fuel in extended exercise.”

When two of the original runners came back for another scan two-weeks later, an even more fascinating image turned up – the myelin appeared to have completely rebounded.

Of course, this study hasn’t been peer-reviewed and the sample size is quite small. Some also wonder whether the difference between scans could simply be caused by dehydration.

The scientists involved don’t think so, though.

“In our opinion, this is not the case. We saw that there is no shrinkage of the brain at all.”

This is important because dehydration will cause the brain to shrink overall.

I imagine we’ll be hearing more about this in the future.

For now, it doesn’t look like you have an excuse to give up running.

At least for now.

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