Spring is finally here, and it’s time for your first sunny morning run in the park. Physical activity is absolutely great for your overall health, but is it also good for the intestinal flora? Some say it is, but I wouldn’t be so sure about it.

There is a common misconception that you can eat whatever you want as long as you exercise. In fact, this statement is only backed up by a few studies. The most famous one is an Irish study in which scientists studied professional athletes from an international rugby union squad. The results provided evidence for a beneficial impact of exercise on gut microbiota diversity.

Case closed? Nope. The rugby players didn’t just exercise more than the participants in the control group, they were also eating a more varied and balanced diet. What if it’s all about the food? If you exercise a lot, your will probably eat more and thereby provide the gut bacteria with more fibers. However, this doesn’t always happen. Just because you exercise, it doesn’t necessarily mean that you eat well.

And as always, the results are affected by what the scientists are looking for. Other studies show that both mental and physical stress can have harmful effects on your gut flora. Let’s have a look at this Norwegian study in which scientists looked at soldiers during a 4-day cross-country ski-march. The study showed an association between the stressful military training environment and increased intestinal permeability, also known as leaky gut.

Blood and stool samples were collected before and after the ski-march to measure inflammation and stool microbiota. The results showed an increased amount of potentially harmful bacteria in stool from participants who had experienced a lot of mental and physical stress. There were also less of the good bacteria, the ones that normally fight inflammation and help strengthen the immune system. To avoid these problems, the findings suggest that the soldiers eat high-fiber foods prior to stressful activities.

Animal research has provided evidence for a beneficial impact of exercise on gut microbiota diversity. That’s usually considered a good thing. But if you look closely, the results are often similar to the ones in the Norwegian study. They often show an increased amount of potentially harmful bacteria, and less of the good ones.

Sounds complicated? It gets worse. A recent study suggest that if you’re skinny, endurance exercise is good for the intestinal flora. But if you’re overweight, the same kind of exercise may have negative effects. Simply put, people with happy guts and well-balanced intestinal bacteria will get the best results from their workouts.

This study has been all over the Internet lately, often treated as evidence when it comes to the supposed benefits of exercise. But the scientists had their eyes set on increased production of butyric acid (butyrate is good for gut health) – and did not look for potential inflammation caused by the heavy exercise.

And remember, the results may have been affected by whatever the participants were eating at the time. As said before, high-intensity workouts will probably make you hungrier. Most of the time, the participants were free to eat whatever they wanted. And if you look closely, you will see that their diets consisted of lots of insoluble fiber. Yup, that’s right. Great foods for the butyrate producing colon bacteria.

Time for the conclusion. Simply put, exercise is not necessarily the key to a well-balanced gut flora, at least not on its own. Exercise can alter the composition of your gut microbiome, but we’re not completely sure if it’s always for the better. Further research is definitely needed.

Leading a healthy lifestyle is a complex task, and there are many factors contributing to overall health. Exercise is a key factor, but don’t forget about diet, friends, sense of meaningfulness, healthy amounts of stress, a good night’s sleep, fresh air, clean water, self-esteem, and the list goes on. Every single one of these things will affect your intestinal flora. But all-in-all, what seems to be the most important factor? That’s right, you guessed it: diet. In fact, a few simple changes can completely transform your health.

Regular physical activity is one of the most important things you can do for your health. But don’t forget to keep your gut happy.

This is a guest post. The opinions expressed are the writer’s own.