You would be a little hard pressed to think that running on a treadmill, lifting weights or climbing stairs might have a positive impact on the microbes which inhabit your gut, but the science on the topic is becoming quite clear: exercise leads to a healthier microbiome.

In a study published in Bioscience, Biotechnology & Biochemistry, rats were separated into two groups. One group had access to a running wheel, whilst one didn’t. Healthy rats, when given the option, will run for extended amounts of time so the groups were labelled the ‘exercised rats’ & ‘sedentary rats’. The running rats averaged a total of 3.5km per day (not bad for those tiny legs) & produced twice the amount of beneficial short chain fatty acid butyrate in their guts than the sedentary rats did. Butyrate is a known byproduct of fibre fermentation by healthy microbes; it is highly anti-inflammatory & has a positive impact on the gastrointestinal tract. Exercise seems to stimulate butyrate’s production which leads to a healthier gut. A healthier gut has also been shown to have a positive impact on managing your weight. Pretty cool stuff.

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But there is more weight to this argument than an experiment on rats. Another study published in Gut tested the microbial diversity of the national Irish rugby squad & found they had significantly higher microbial diversity (an indicator of microbiome health) than regular non-athletes of the similar age & BMI. They also found they had healthier inflammatory & metabolic markers in the blood.

Dr. Tim Spector, a UK based researcher specialising in gut microbes has also written of the fact that the most consistent variable which can determine microbiome diversity is the amount of exercise one does (see his book The Diet Myth).

So could it be that exercise alone is like taking a probiotic for your microbiome? It certainly seems so, but there could be other factors at play here. Could it be that those who exercise also take more interest in eating healthier? Something we all know contributes to a healthier microbiome. Could they also have a higher incidence of taking supplementary probiotics or consuming fermented foods?

Or could it be more mechanistic in nature? It is my belief, & permission to theorize here, that the lactic acid produced during exercise has a beneficial effect on the microbiome as we have many health promoting bacteria like the lactobacillus family which love & produce lactic acid. Do you remember when you were young, or perhaps even now exercising to the point where you wanted to throw up? That’s actually your body telling you your lactic acid has moved into the stomach & is overloading it to the point of hitting the ‘eject’ button.  Obviously, this is not a healthy situation, but I believe micro-doses of lactic acid being pumped from the working muscles & naturally diffusing into the stomach may provide nourishment to our friendly microbes. We’ll see if this theory holds true over time.

Regardless, what we know of exercise extends far beyond just healthier microbes, so it is essential that you incorporate healthy amounts of exercise into your daily routine.

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