Can Exercise Impact Our Gut Microbiome?

By now we know that the bugs in our guts are influenced by what we eat. Kombucha, sauerkraut, kimchi, and natto all have the ability to add beneficial strains to our microbiomes. In turn, the communities of bacteria and fungi living in our gut contribute to a plethora of health-related conditions we experience every day, including how anxious or happy we are, how often we’re having bowel movements, and even how well our immune system is functioning.

As more and more research continues to flow out of laboratories, we’re also starting to learn how the way we live has a direct impact on our microbial friends and foes. For example, did you know that how often and how intensely you’re exercising could impact your microbes?

In a study published last November, researchers analyzed the guts of 32 women and men who didn’t exercise. Over the course of six weeks, volunteers ramped up their exercise routines, starting with walking and ending with an hour of vigorous jogging or cycling. Gut samples were collected again, and then once more six weeks later after another period of no exercise.

Interestingly, all of the participants saw changes in their microbiomes due to exercise, even though the individual bacteria and fungi varied greatly amongst volunteers. The greatest changes, however, were seen in lean participants versus obese ones.

Lean participants saw increases in their short-chain fatty acid-producing gut bugs, which is significant, as short-chain fatty acids are the main source of fuel for the lining of the colon.

Is all this to say that it’s not beneficial for obese individuals to exercise? Not at all. Obviously exercise has numerous benefits for people of all sizes, and more research is being done to identify the impact of exercise on microbiota in everyone. And one other thing that was clear: the researchers of this study found that after the six weeks of no exercise, the microbiomes of everyone involved went back to its old ways.

In another study, scientists looked at the effects of low- versus high-intensity exercise on the microbiome. Researchers found that low-intensity movement, such as casual biking, walking, or yoga, helped to increase bowel transit time (that’s how quickly food is passing through you and out the other end).

Ideal bowel transit time is 18-24 hours, but most of us are clocking up to 72 hours, on average, which is pretty nasty. To illustrate why, think of having a bowel movement like taking out your trash. If you don’t do it regularly, it starts to rot and stink. The same thing happens in your body. If you’re not going to the bathroom at least once per day, your internal trash is sitting around, and could cause major issues as your body is exposed to the bacteria you’re not emptying out.

By increasing this transit time, low-intensity exercise was shown to reduce the risk of colon cancer, diverticulitis, and inflammatory bowel disease. On the flip side, these researchers also found that high-intensity exercise (think HIIT training) induced gastrointestinal symptoms such as heartburn or diarrhea in some people. While it’s unlikely that this would be an issue for an experienced exerciser, it’s something to keep in mind if you’re thinking about upping your exercise game.

To recap, here’s how you can use exercise to keep your gut microbes in good shape:

  • If you don’t already exercise, start small. Incorporate 30 minutes a day of walking, light jogging, yoga, or cycling into your routine.
  • As you feel comfortable, increase your intensity to up to an hour per day, but cut back if you start noticing any adverse symptoms.
  • Keep it regular. The research shows that when we stop exercising, our microbiome reverts back to its old state, so consistency is important.
  • Test your bowel transit time and see if it increases with exercise. To do this, eat a bunch of beets and then keep track of how long it takes to see them in your stool. That’s your transit time.
  • Like what you’re doing. We also know from the research that stress contributes to negative changes in the microbiome, so pushing through something you hate is counterproductive.

While the research on the microbiome is still underway, tried-and-true exercise is always a safe bet for improving your overall health and wellness.

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