Is your marathon eating your brain?

Have you ever finished a marathon and wondered if the resulting brain fog was something to be worried about? Turns out, your brain is probably adapting to the challenging task of going the distance in ways you weren’t aware of. New research, reported in Technology Networks, reveals that marathon running can temporarily deplete brain myelin, a fatty substance that helps transmit electrical signals between neurons. But don’t panic yet—this can actually be a normal response to intense endurance exercise.

What is myelin and why does it matter?

Myelin is essential for brain function. It insulates nerve fibres, ensuring that signals travel efficiently and quickly through the brain and spinal cord. It’s composed mostly of lipids, or fats, and has always been thought of as just a structural element. But researchers are starting to think that myelin may have a second, unexpected role—acting as an energy reserve. According to a recent study by Carlos J. Matute and his team at the University of the Basque Country, intense endurance exercise, like running a marathon, could tap into myelin lipids as an alternative fuel when the body is running low on glycogen (the stored form of carbohydrate). While this concept is still new, it raises intriguing questions about the long-term effects of frequent, intense exercise on the brain.

The science behind marathon running and myelin

The researchers used MRI technology to monitor brain myelin levels in 10 marathon runners before and after completing a 42.2 km race. The results were striking: the runners experienced a temporary reduction in myelin content, particularly in regions crucial for motor functions. These changes were most significant immediately after the race, but by two months post-race, the runners’ myelin levels had fully recovered. This suggests that marathon running does indeed impact brain myelin, but the changes are reversible.

A temporary setback for a big reward

While the drop in myelin is temporary, the concept of “metabolic myelin plasticity” is fascinating. During periods of intense metabolic stress, such as running a marathon, the brain may tap into myelin lipids for fuel, helping to support cognitive and neural function. This adaptive response ensures that the brain can keep functioning even when other energy sources, like glucose, are in short supply. However, it’s not known whether repeated cycles of myelin depletion and recovery have long-term consequences, especially for athletes who regularly engage in endurance sports.

What does this mean for runners?

If you’re a marathoner, don’t worry—this brain drain isn’t something to lose sleep over. The brain’s ability to recover myelin within a few months is reassuring, and it’s likely that most runners won’t experience any lasting effects. However, this does highlight the importance of allowing for recovery between races and acknowledging that our brains, much like our muscles, need time to repair. So next time you feel that post-race brain fog, just remember—it’s temporary, and your brain will bounce back. But it might take a little while to catch up with your legs.