A recent study suggests that marathon running can lead to significant, albeit temporary, changes in brain structure. Researchers found that after a marathon, runners experienced a noticeable reduction in myelin, a fatty substance that insulates neurons and speeds up brain communication. This suggests that the brain may tap into myelin’s fat reserves as an emergency energy source during extreme endurance events.
Marathons, covering 26.2 miles, push the human body to its limits. Initially, the body relies on stored carbohydrates (glucose) for energy. However, these reserves eventually deplete, forcing the body to switch to burning stored fat. Previous research on rodents indicated that the brain might utilize myelin as a fat source under such circumstances. Myelin, composed of 70% to 80% lipids (fats), plays a crucial role in protecting and facilitating communication between brain cells.
To investigate this in humans, researchers conducted MRI scans on ten marathon runners (both city and mountain runners) up to two days before and a day or two after a marathon. Some participants also underwent scans two weeks and two months post-marathon. Before the race, myelin levels were similar across all runners (measured using an indirect biomarker). Post-marathon scans revealed substantial myelin decreases in brain regions associated with motor coordination, sensory processing, and emotional integration. Follow-up scans showed myelin levels partially recovering after two weeks and returning to baseline after two months.
These findings corroborate rodent studies suggesting that the brain might use myelin lipids as an energy reserve during periods of high demand. However, the researchers acknowledge the small sample size and emphasize the need for further research to validate these results and fully understand this phenomenon. Future studies could explore whether myelin usage varies depending on the type of prolonged activity or stress. Additionally, research is needed to determine if these temporary myelin reductions lead to any noticeable physical or cognitive changes.
While elite runners are generally healthy and often have longer lifespans, it’s unlikely that this temporary myelin dip significantly impacts their health. However, studying this phenomenon in runners could provide valuable insights into brain energy metabolism in other contexts, such as neurodegenerative disorders linked to permanent myelin loss. Further research is warranted to explore the potential implications of these findings for brain energy metabolism.
The researchers conclude that additional studies are crucial to fully understand the potential relevance of these findings to brain energy metabolism.
