New studies show that running marathons may temporarily sap the brain’s myelin — a fatty substance that covers and insulates nerve fibers — which could signal that the brain draws on its own structural resources for energy during extreme endurance activities.
An MRI scan study of marathon runners showed significantly reduced myelin levels immediately after the race, after two weeks their levels returned back to near baseline values. This suggests that in states of severe physical activity where conventional fuels such as glucose are depleted, the brain could use myelin instead as an energy source.
Although this phenomenon may seem alarming, researchers say the brain’s capacity to quickly replenish myelin demonstrates its resiliency and adaptability. The temporary reduction in myelin may not be seen as a sign of long-term injury but may rather reflect the brain’s ability to swiftly adapt to energy demands required by intense physical activity.
Yet this finding highlights the need for both adequate recovery and adequate nutrition for endurance athletes. In fact, allowing your body to rest and recharge the nervous system should be priority after a race to help your brain repair itself and sustain its health.
To paraphrase: The short-term structural changes in the brain resulting from marathon running must be addressed with proper care and recovery — however, the brain demonstrates a powerful capacity for recovery, so if we afford it the recovery time it needs, these effects will be transitory and manageable.
You can access the full study here: Nature Metabolism – Reversible reduction in brain myelin content upon marathon running
For a summary and additional details, the study is also indexed on PubMed: PubMed – Reversible reduction in brain myelin content upon marathon running
