But it’s still unclear exactly how exercise causes changes in the community of microorganisms living in our gut, although there are several theories, Woods says.
“Lactate is produced when we exercise, and it could serve as fuel for certain bacterial species,” he says. Another potential mechanism, he explains, could be exercise-induced alterations in the immune system, particularly the gut immune system, because our gut microbes are in direct contact with immune cells in the gut.
Exercise also causes changes in blood flow to the intestine, which could affect the cells lining the intestinal wall and in turn lead to microbial changes. Hormonal changes caused by exercise could also lead to changes in gut bacteria. But none of these potential mechanisms “have been definitively tested,” Woods says.
Some elite athletes often suffer from exercise-induced stress due to the high intensity training they do. As much as 20-60% of athletes suffer from stress due to overtraining and insufficient recovery, according to some estimates. But the bacteria in our guts may help control the release of hormones triggered by exercise stress, while potentially helping to release mood-enhancing molecules. They can also help athletes with some of the intestinal issues they are experiencing. However, further research is needed in this area.
But we can still learn a lot more about how our physical activity affects the creatures living inside our intestines, such as how different types of exercise and their duration can alter the microbial community. It can also differ from individual to individual, depending on their existing gut residents as well as BMI and other lifestyle factors, such as their diet, stress levels and sleep.
As scientists continue to uncover more and more secrets hidden in our gastrointestinal tracts, we may find new ways to improve our health through the vibrant and diverse communities of organisms that call us home.
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