Rather unlikely. We ourselves do intensive research in the field of sport and the immune system. One can say that this triggers inflammatory reactions. There are actually people who, after running a marathon, have changes in the gastrointestinal tract that resemble ischemic colitis, an inflammation of the large intestine. This is not often, but there are Case reports.
A symptom that is most common in such people is blood in the stool. What’s behind it?
It is a gradual process. First, the intestinal wall becomes more permeable. At some point there is damage to the mucous membrane. In animal experiments we were able to show that more cells die in the intestine, Called apoptosis. So there is a kind of abrasion taking place. Of course, new cells are reproduced, but at times the system is overwhelmed and large erosions can develop, which are accompanied by bleeding.
So is sport generally bad for the gastrointestinal tract?
Everything has two sides. Of course you can say to yourself: sport is murder. Yes, it’s true – some people drop dead in the process. But most of the time there was already a certain amount of previous damage. It is also true that maximum stress can damage the intestinal wall. However, the question is more: How often and how much do I stress myself over the long term? To draw the conclusion from this that sport is generally bad, I think it is wrong. Because the intestines can also be trained. Stimulating the digestive tract through physical activity can certainly be beneficial. This is a recognized therapy method for constipation or flatulence.
From athletes to athletes
Frank Mooren likes to go hiking and running. He used to play a lot of volleyball. For the sports medicine physician, exercise is a necessity for the organism: although people now have a completely different lifestyle, they have essentially the same genes as the hunter-gatherer who walked 30 to 40 kilometers a day. That is why it is important to integrate exercise into everyday life.
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According to studies, you can certain foods, such as energy drinks, cause digestive problems in connection with exercise. Why is that?
Consuming a high concentration of carbohydrates causes an osmotic gradient, which draws water into the digestive tract. This delays the emptying of the stomach, hinders the necessary water absorption and can cause cramps, nausea and diarrhea, for example.
How do I avoid this, in other words: What should I not eat or drink before exercising?
The glucose content of drinks or gels should not be more than six percent. Overall, you shouldn’t consume any high-calorie foods before exercise. That just creates problems if you don’t have adequate blood flow in the gastrointestinal tract. The ingredients cannot be removed properly.
That’s interesting. Many athletes swear by energy bars before and during competitions.
Of course, there are also relevant recommendations as to how long you should be exposed to glucose. That is reasonable. But in a form that is easy to open. It makes perfect sense to consume a mixture of different carbohydrates.
Why?
The transport capacities for glucose in the gastrointestinal tract are limited. You can get around this a bit by opting for a mixture of glucose and fructose or adding more carbohydrates. Adequate hydration is also important. Of course not too much either, otherwise there may be a lack of salt, a so-called exercise-induced hyponatremia.
How long before exercise should I stop eating? One often hears the recommendation: two hours. Do you agree?
Yes, that’s about right. Or, if you eat something, you should only eat easily digestible food.
That would be for example?
A muesli or oat bar or dried fruit. You should check the snacks for their glucose content and how well you can digest them.
You published a study in 2020where you let people exercise and then did their blood tests. What was the result?
For this study, we deliberately selected people who were not athletic because we can induce gastrointestinal disorders in them a little easier. However, such people do not go to their limits so easily. The changes that we induced in them through a 45-minute exercise session were therefore not particularly strong. However, we did find evidence of epithelial damage in the blood of the test subjects. However, that has improved after taking the bacterial strain for over four weeks Escherichia coli Nissle 1917 had taken. When they did the same exercise again after this time, the concentrations of the damaging proteins were significantly lower. In between they did not do any sport, so that a training effect can be ruled out.
What are probiotics?
The term is not clearly defined. These are products that contain viable microorganisms such as strains of bacteria such as Escherichia coli Nissle 1917. Foods to which various microorganisms have been added are also considered probiotics. Yogurt, which contains more lactic acid bacteria than usual, is particularly popular. However, these are generally necessary to convert milk into yoghurt through fermentation. Fermented foods such as sauerkraut and kimchi are also probiotics.
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How do you explain this effect?
One possible mechanism is that the bacterial strain has the reduces oxidative stress in the gastrointestinal tract. This has already been shown for other probiotics.
So would you recommend that athletes take probiotics?
I would like to put that into perspective. I am not a fan of recommending a wide variety of remedies to athletes. But I can say one thing: In principle, you can’t go wrong with probiotics. Not only in ours, but also in other studies have used this positive Effekte shown. They are not always very clear, they are often just individual reports, or the effects are not shown consistently in all studies. For example, there is research that has shown that the Performance of marathon runnerswho had taken probiotics did not drop as much in the last section of the route as in a control group.
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