⬇️ Prefer to listen instead? ⬇️
- Endurance exercise can trigger the brain to break down myelin for energy during extreme energy depletion.
- Mouse studies showed temporary myelin loss after three hours of fasting treadmill activity, with full recovery in seven days.
- Myelin isn’t just insulation—it may act as an emergency energy reserve during fuel scarcity.
- Oligodendrocyte cells help rapidly repair degraded myelin, showing how well the brain can bounce back.
- Understanding myelin metabolism could improve treatment plans for MS and other brain diseases where nerves break down.
When you are under a lot of physical stress, like doing long exercise without food, your brain might do something big to keep working. It starts using parts of its own structure for fuel. New research shows that myelin, the fatty stuff covering your nerve cells that’s needed for signals to move fast, can be broken down for a short time to get energy. This happens mainly when fuel is very low for a long time. This ability to adapt shows us new things about how the brain uses energy. It also shows us how tough endurance exercise is on the brain. And it tells us about long-term effects on thinking and brain health.
What Is Myelin?
Myelin is a fatty covering that wraps around nerve cell fibers. It helps signals move fast and well through the central and outer nervous systems. Think of it like the plastic coating on electrical wires. Without it, signals slow down, get weak, or don’t make it. Cells called oligodendrocytes in the central nervous system and Schwann cells in the outer nervous system make most of the myelin.
In the brain, myelin makes up some of what scientists call “white matter.” This is different from “gray matter,” which has the main parts of nerve cells. Myelin is not just a dead material. It plays a part in how nerve cells talk to each other. It also helps the brain change and helps you think well.
Before, people thought myelin was just needed for structure. They thought it was key for moving, feeling things, and thinking well. But new proof shows it also helps the brain use energy. When conditions are very bad, the brain might use this material to fuel itself. This shows a way the brain survives that wasn’t known before.
Brain Energy Demands: The Brain Needs Lots of Energy
The human brain needs a lot of energy. It is only about 2% of your body weight, but it uses almost 20% of the body’s total energy when resting (Attwell & Laughlin, 2001). That energy is mainly used to keep nerve cells talking to each other. This is what lets you do everything from simple movements to complex thinking.
Primary Energy Source: Glucose
Normally, glucose is the main fuel the brain likes best. Glucose makes ATP, which is the main energy for cells. Glucose gives the fuel needed to keep nerve cells working through processes like glycolysis and oxidative phosphorylation.
Backup Energy Sources
When there isn’t enough food or energy is needed fast, the brain can switch to other fuels:
- Ketone Bodies: These come from using fat for energy. The liver makes them when you are fasting or on a low-carb diet.
- Lactate: Muscles make this during exercise. Lactate can give nerve cells energy in certain cases.
- Aerobic Glycolysis: Some parts of the brain (especially in kids or when very active) make energy this way. It’s not as good, but it’s fast.
But even with these other fuels, there are limits. When you do very long endurance exercise without eating, like running a marathon while fasted, you use energy faster than you take it in. This pushes the brain to use emergency plans to keep working.
Energy Deficiency During Endurance Exercise
Doing long exercise—like running, biking, or swimming for many hours without eating enough—can empty your body’s energy stores. Muscles use up glycogen and fatty acids. The brain, which mainly needs a steady flow of glucose, also starts to feel the lack of fuel.
The brain still needs energy to keep the body stable, put together what your senses take in, control thinking, and make you move. These needs don’t stop just because you are stressing your body physically. If there isn’t enough fuel in the body, the brain must find a way. This is where the idea of breaking down myelin comes in. It means breaking down parts of the brain’s structure to get energy.
Energy Limits Hit the Brain First
The brain cannot store a lot of energy like muscles or the liver can. So, using a lot of energy for a long time without taking fuel in affects the brain early and strongly. If there isn’t enough glucose or ketone bodies for long periods, nerve cells don’t work well. Instead of risking a big shutdown, the brain might use unusual methods. It might get energy from parts of its own tissue.
New Insights: Myelin Breakdown as Backup Fuel
Important research on mice that did hard treadmill exercise while fasted for three hours showed signs that myelin broke down for a short time. Within 24 to 48 hours, scientists saw changes in key brain areas. This included the corpus callosum, which connects the sides of the brain, and the visual cortex, which helps you see.
This shows myelin is not just a passive covering. It is a usable store of energy parts, maybe fatty acids and cholesterol-based fats. The brain can use these when fuel is low.
Being Reversible Shows Damage Control
What makes this finding very interesting is that it can be undone. Myelin levels went back to normal within seven days after the exercise. This means the body has systems built in to fix things after needing a lot of energy. This shows how well the brain can bounce back and rebuild.
Being able to bounce back is key. If the brain couldn’t fix myelin quickly after losing it many times, it could leave nerve fibers open. This could slow signals down or hurt thinking and moving in the end.
Biology of Rebuilding: The Role of Oligodendrocytes
The brain can rebuild myelin that is lost or broken down. This is done by oligodendrocyte precursor cells (OPCs). These are a special type of cell. These cells stay active throughout life. They can change into full oligodendrocytes, which then wrap nerve fibers with new myelin covers.
What Happens Around You Matters
New studies show that brain activities can help these myelin-making cells. This includes exercise, learning, talking with others, and getting better after injury. For athletes who do endurance sports, or those getting better after a brain injury, this could be good news. More nerve cell activity might help myelin repair after stress causes loss.
Myelin Changes
This whole process changes what we think myelin is. It is not just a dead cover that protects things. It is an active part of the brain that can be changed based on what is happening around you and inside your body. When myelin breaks down and rebuilds in this way, it is part of a system that adapts. It works somewhat like how muscles break down and grow stronger when you train physically.
Implications for Endurance Athletes and Others Pushing Limits
Athletes who push their bodies hard now need to think about more than just drinking enough, energy stores, and muscle tiredness. Not eating enough during hard effort could cause temporary problems with thinking. This happens because the brain’s energy is not balanced.
Short-Term Help vs. Long-Term Issues
For a short time, losing some myelin might help you stay sharp mentally when you need it most. It could help you keep your movement control, make decisions, and take in what your senses tell you. But over time, especially if you don’t rest or eat well to recover, the system that rebuilds things might fall behind.
This brings up worries about:
- Burnout
- Mental fog
- Mood changes
- Thinking problems that come with age
Pushing your body too hard doesn’t just hurt muscles and joints. The brain, especially its white matter, could be taking silent hits that add up over time.
Potential Benefits and Biological Trade-offs
Every emergency system has a cost. Using myelin as fuel also has a cost. While it shows how our bodies are built to survive, breaking down and fixing myelin again and again is not without risk.
Good News: The Brain Can Rebuild
Myelin can grow back in less than a week. This shows how well the healthy brain can bounce back. It gives a hopeful picture for using myelin for a short time. In healthy people who eat and rest well after exercise, the brain can recover with few lasting effects.
Bad News: Chronic Stress Is Another Story
If the breakdown happens faster than the brain can fix it, or if it happens in people whose bodies aren’t good at making myelin (like older people or those likely to get brain diseases where nerves break down), this could lead to long-term problems.
Using the brain’s “wiring cover” again and again without letting it fix itself can lead to slower thinking, slower reactions, and possibly make the brain more likely to get inflamed or break down in structure.
Impacts in Neurology: Rethinking Disease and Repair
This discovery opens up new ways to think about brain diseases like multiple sclerosis (MS). In MS, the body’s defense system attacks and destroys myelin.
Instead of just trying to lower swelling, could new treatments try to help the brain rebuild myelin from within? Could doing things that act like exercise-induced changes help start recovery?
If scientists can figure out how to use the same signals that cause myelin to grow back after it’s used during endurance activities, it could mean a big shift in how we see and treat conditions that damage myelin.
Brain Metabolism as a Survival Engine
This new proof shows the brain is much more than just a control center. It is a system that adapts in many ways, especially when under pressure. The idea that its covering (myelin) could also be emergency fuel shows deep survival instincts aimed at keeping things working in very tough times.
It’s a hard choice: needed energy now, possibly making signals slower later. But it also shows a system built to recover. This is a key quality of being able to handle stress.
Unanswered Questions and What’s Next
This research area is still new. A lot is still unknown about how and why the brain tells itself to use myelin under stress.
Future studies could look into:
- What specific things start the breakdown of myelin?
- Can we control or stop this process with medicines?
- Are some people’s genes better at handling repeated breakdown?
- How does doing endurance training for a long time change the brain’s structure?
Learning about these things could change how we support people who push their limits, treat brain problems, or help people keep their thinking skills throughout life.
Takeaway: Rethinking Brain Energy and How it Handles Stress
This research makes us think again about what we know about how the brain uses energy. It is no longer enough to think of glucose as the only brain fuel. When under extreme stress, the brain uses deeper stores, like myelin, to keep working.
For people who love endurance exercise, people who care about brain health, and brain scientists, these findings confirm a main truth:
🧠 The brain is built to survive just like any other part of the body—with many ways to keep going, even when it feels like it has no fuel left.
Whether you are timing your laps, studying brain science, or working to keep your mind sharp as you get older, knowing how myelin helps both performance and recovery can change how we train, get ready, and recover.
