New research published in Nature Metabolism indicates that the brains of marathon runners can utilize their own myelin for emergency energy during extreme physical exertion. This finding offers a glimpse into the brain's sophisticated survival mechanisms when glucose reserves are critically low.
The study utilized MRI scans to observe marathon runners before and after races. Researchers identified a significant, yet temporary, consumption of myelin – the protective sheath around neurons – in brain regions vital for motor control and the integration of sensory information. This phenomenon is characterized as a temporary survival strategy, with myelin levels returning to their pre-race state approximately two months post-event. The process is fully reversible, highlighting the brain's remarkable plasticity even under severe physiological stress. This process has been termed "metabolic plasticity of myelin."
Dr. Marcelo José da Silva de Magalhães, a neurosurgeon, explained that oligodendrocytes, the cells responsible for myelin production, can indeed use myelin as an alternative energy source during extreme stress. Myelin, composed of approximately 70-75% lipids, is crucial for efficient nerve impulse transmission. Once the intense demand of an event like a marathon subsides, the brain actively synthesizes new myelin to restore neural integrity, a process that typically takes from two weeks to two months.
Dr. Melissa Ulhôa, a physiology specialist, noted that highly trained marathon runners possess bodies exceptionally adapted to extreme physiological demands. During prolonged exercise, as carbohydrate stores are depleted, the body shifts to alternative metabolic sources, including ketone bodies for both the brain and muscles. Strenuous exercise can also trigger lactate production in muscles, providing a rapid energy source when oxygen is limited.
While the immediate implications for athletes emphasize the importance of recovery and understanding the body's limits, this research opens new avenues for understanding brain resilience. The brain's ability to tap into its own structural components for energy during critical periods underscores a sophisticated self-preservation system, suggesting that with adequate recovery, the body's systems can restore themselves.
This finding is particularly relevant in countries with large running communities, such as Brazil, which hosts over 2,800 official street races annually and has a significant presence on platforms like Strava, uniting over 19 million users. In Brazil, approximately 2.45% of the population runs, with this figure rising to 5.32% among those who exercise regularly.