After marathons, the nervous system loses a substance, the deficiency of which can lead to neurodegenerative diseases
If there is a complete consensus in the world regarding the benefits of moderate physical activity, then many doctors call high-performance sports evil for good health. Further evidence of this was discovered by scientists who examined the brains of marathon runners after the race. Their goal was to understand whether this organ, made of fat, would begin to eat itself when the glucose ran out. But the results were quite unexpected.
Long-term endurance training mobilizes energy reserves throughout the body to meet energy needs. Carbohydrates are the main source of fuel, which is provided by the breakdown of glycogen in the muscles and liver. As glycogen stores are depleted, the body begins to rely more on stored fat.
Science has long established that with prolonged physical activity, the body’s glucose reserves are depleted – and then it begins to burn fat. Spanish scientists, the authors of the published study, proceeded from the fact that one of the main consumers of energy in humans is the brain. In addition, it is one of the richest organs in fat. Therefore, we decided to check what happens to the fat composition of the brain in marathon runners.
Fat is the most abundant source of energy
in the body compared to carbohydrates, and can serve as a constant source of energy for long-term endurance training.
“Fats in the nervous system play an extremely important role as the main electrical insulator of nerve endings,” says the famous geneticist from the USA Dmitry Pruss, “This is myelin – a two-layer layer of the cell membrane of special cells wrapped in a spiral of more than 40 turns, a natural insulator of nerve fibers (neurons) . Myelin-forming cells are true champions in cell membrane growth. Their surface area is tens of times higher than their closest competitors for the championship title, and they can synthesize new sections of the surface membrane more than 100 times faster than average. Myelin contains lipids (that is, fats) – almost half by weight. But 40% of the mass is water in the form of the thinnest layers of cytosol between the lipid layers. The thinnest layers of fat and water give myelin its white color, and it is because of this that the areas of the brain richest in nerve endings are called white matter.”
Layers of water in myelin can be detected by MRI – this is exactly the kind of study that researchers from Spain conducted for marathon runners. And the results were shocking: magnetic resonance imaging data showed massive myelin loss after long runs. The myelin content in the runners' brains dropped dramatically. Almost half of the myelin has disappeared in some parts of the white matter! The nerve networks responsible for motor functions were especially severely affected. Two weeks later, a follow-up MRI showed that the myelin had mostly recovered, although not completely. “Our results suggest that marathon running reduces myelin content throughout the gray and white matter of runners’ brains. Subsequently, this loss of myelin is partially restored, since the values steadily increase through
two weeks after completion of the load,” notes the work of Spanish scientists.
“Loss of myelin is a well-known and notorious thing in medicine. Multiple sclerosis is the best known of the demyelination diseases, in this case associated with the immune system attacking myelin, but there are other diseases, each worse than the other. Whether the brain actually eats its own myelin during marathons, or whether something else influenced the MRI results, is not yet clear. Brain dysfunction in marathon runners has also not been studied. And what happens after a long hunger strike and similar fat-destroying situations has also not yet been studied,” states Dmitry Pruss.
If we talk about the risks of neurodegenerative diseases (Alzheimer’s disease, Parkinson’s disease) in marathon runners, nothing has been fully studied yet. Experts say it's more likely that after a race, the effects of myelin loss are short-term rather than chronic. One doctor who practices racing said that he would not dramatize the situation: “When running fast (distances up to about 5 km), the head really doesn’t work well – lactic acid under load completely turns off thought processes. After finishing, I would understand where to go next. And in general, what time of day is it? But a marathon is not about running fast, and your head works fine while running. Even before the finish, having depleted my glycogen, I had no problem thinking about my training plan for the next six months and calculating my finish time based on my current pace. Your vision suffers – your attention is focused in a narrow cone, you can’t see the fans. That is, subjectively it seems to me that the brain has enough glycogen. But about an hour and a half after the race, you can go home by car, there are no cognitive problems either. Two days after the finish is enough to restore the water-salt balance. Normally, one day is enough if there were no medical problems at the race.”
“The ultrarunners I have met are the most intelligent, emotionally balanced and reliable people. So I strongly suspect that everything is fine with the central nervous system of these people. But nothing extreme can ever be done without harm to health, there is no dispute about that either,” marathon runner Alexey told MK.
In addition, the results of the study raise a logical question: how dangerous is it to lose weight (mechanisms of fat burning when losing weights are approximately the same). And the authors of the publication are also thinking about this, but do not yet know the answer to the question: additional research needs to be carried out.