According to a new study, running marathons could be linked to brain damage.
However, the study noted that the impact is temporary and reversible.
Running marathons is bad for your brain (but only temporarily) https://t.co/eVuqlqGu6i
— Matt Lieberman🇺🇦 (@social_brains) March 27, 2025
The study, published in the Nature Metabolism Journal on March 24, stated that scientists observed eight men and two women and found their myelin levels “diminished by severe exercise.”
Myelin is an insulating layer around nerve fibers, primarily consisting of fats and protein.
“Myelin content … is substantially reduced upon marathon running in specific brain regions involved in motor coordination and sensory and emotional integration, but recovers within two months,” the study found.
The body may turn to fat reserves, such as myelin in the brain, as an energy source after other sources, like glucose from broken-down carbohydrates, are depleted.