High endurance activities like marathon running can temporarily damage the brain, as they cause the brain to draw on a metabolic “safety net” to keep going when other energy sources are depleted.
The study, published in the journal Nature Metabolism and reported in Science Alert, measured how marathon running impacts the brain in 10 runners, eight men and two women.
Researchers used MRIs to measure an indicator of myelin content two days after the subjects completed a marathon. Myelin was found to be substantially reduced in specific brain regions involved in motor coordination and sensory and emotional integration.
These findings suggest that myelin, which is primarily composed of fats and proteins, can become a reserve of last resort for the brain after carbohydrates are depleted. The study authors call this hypothesis metabolic myelin plasticity, noting that it will require further research.
Myelin forms an insulating layer, or sheath, around nerves, including those in the brain and spinal cord. It allows for electrical signals to transmit quickly and efficiently along the nerve cells. When the myelin sheath becomes damaged, those signals can slow or even stop. This can translate into difficulty walking or seeing, or changes in bladder and bowel function.
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When myelin is lost to disease, it cannot be recovered. At best, treatments can help to slow the progression of the disease, making early detection imperative.
According to the Mayo Clinic, the most common and well-known demyelinating disease is multiple sclerosis (MS), in which the immune system attacks the myelin sheath or the cells that produce and maintain it. While 1 in 500 people have MS, all of us become more vulnerable to losing myelin as we age.
However, in follow up measurements researchers also found that myelin levels in the marathon runners eventually recovered, and while the study highlights how extreme endurance exercise can temporarily diminish myelin, other studies suggest that moderate continuous exercise can have the opposite effect – enhancing myelin sheath regeneration.
In this way, exercise can help to treat and even prevent demyelination, with physicians recommending that people with MS exercise at least 30 minutes a day, five days a week. Exercise also allows the body to efficiently use dietary fat to increase the two major myelin proteins.
