Yup, another early morning class. Well, it’s not all so bad – my nutrition professor is going to discuss which foods we should be eating to maximize our performance during physical activity (verdict: we don’t know… But it’s probably not a bad idea to eat your greens!). Pretty interesting topic right?
I zoned out, AGAIN. Just once I’d like to get through one full lecture with full concentration. Anyways, as I was wandering the recesses of my mind, I stumbled upon a terrific blog idea: How does physical activity impact our gut bacteria and vice-versa?
As mentioned in previous blogs, the gut microbiota plays a crucial role in human health; it prevents the survival of pathogenic bacteria (these critters harm you and can even kill you), stimulates the proliferation of epithelial cells (i.e. the cells that line your intestines and are thus in direct contact with the bacteria living there. Proliferation is a good thing – it allows the lining of the intestines to replenished frequently and remain rejuvenated) (1) and helps to digest certain nutrients that we can’t digest on our own. It’s a love-hate relationship, really; while we require the gut flora to keep us alive and well, an altered gut bacteria has been associated with many diseases such as obesity, heart failures, cancer, and diabetes (see previous blogs).
Now, is there a correlation between physical activity and a healthy gut microbiota?
Many studies have shown that physical activity is associated with a healthy microflora. Studies by Dr. Matsumoto and his colleagues have successfully demonstrated that rats following a rigorous running regimen harbor a different gut microbiome composition than control rats whom refrained from running. This showed that rats who did running exercises had a different microbial composition in the gut (2).
So what? Matsumoto investigated his findings deeper, and found that this exercise-induced microbiome produced high levels of an infamous compound known as “butyrate”. Butyrate has been well characterized as a potent suppressor of both colon cancer and inflammatory bowel disease (2, 3)
A revealing study by CC Evans in 2014 built on Matsumoto’s work. Evans and his colleagues demonstrated (through an elegant set of experiments) that mice were able to counter the obesity-inducing effects of a high-fat diet through exercise alone. “But you already knew that !”
The real interesting finding made by Evans was that as the mice ran for greater distances, the lower their Firmicutes:Bacteroides ratio became in the gut (4). If you’re familiar with our previous blog, then you may remember that a lower ratio correlates with weight loss. Essentially, they showed that exercise played a role in preventing obesity by favoring a bacterial composition that is similar to those in lean mice regardless of the diet.
Although, these studies have shown some promising results, you might be wondering if this applies to human beings.
A study on the “fecal microbiota of individuals with different fitness levels” (5) following similar diets showed that people with a higher cardiorespiratory fitness had a greater microbial diversity in their gut. This study by Estaki et al. demonstrated that people who were more physically active had an increase in gut microbial diversity irrespective of the diet, and that diversity is a potent driver of optimal gut health. Additionally, similar to the study in mice, fit individuals showed an increase in butyrate producing bacteria
How does doing exercise change the microbial diversity in the gut?
Further studies are required to fully comprehend the mechanism by which exercise changes the composition of gut bacteria. Nevertheless, one possible theory is that exercise causes lactic acid to be produced in the body, which could be converted by certain bacteria in the gut to butyrate (6).
So if you didn’t already have enough reasons to get to the gym, here’s one more: these studies demonstrate the potential of exercise to be used as a treatment to restore a healthy gut microbiota. We can, quite literally, run our way to a better microbiome.
1. S. Rakoff-Nahoum, J. Paglino, F. Eslami-Varzaneh, S. Edberg, and R. Medzhitov, “Recognition of commensal microflora by toll-like receptors is required for intestinal homeostasis,” Cell, vol. 118, no. 2, pp. 229–241, 2004.
2. M. Matsumoto, R. Inoue, T. Tsukahara et al., “Voluntary running exercise alters microbiota composition and increases n-butyrate concentration in the rat cecum,” Bioscience, Biotechnology, and Biochemistry, vol. 72, no. 2, pp. 572–576, 2008.
3. Tan, Hwee Tong, Sandra Tan, Qingsong Lin, Teck Kwang Lim, Choy Leong Hew, and Maxey C. M. Chung. "Quantitative and Temporal Proteome Analysis of Butyrate-treated Colorectal Cancer Cells." Molecular & Cellular Proteomics 7.6 (2008): 1174-185. Web.
4. C. C. Evans, K. J. LePard, J. W. Kwak et al., “Exercise prevents weight gain and alters the gut microbiota in a mouse model of high fat diet-induced obesity,” PLoS ONE, vol. 9, no. 3, Article ID e92193, 2014.
5. M. Estaki, J. Pither, P. Baumeister et al., “Cardiorespiratory fitness as a predictor of intestinal microbial diversity and distinct metagenomic functions,” The FASEB Journal, vol. 30, no. 1, pp. 1027–1035, 2016.
6. S. H. Duncan, P. Louis, and H. J. Flint, “Lactate-utilizing bacteria, isolated from human feces, that produce butyrate as a major fermentation product,” Applied and Environmental Microbiology, vol. 70, no. 10, pp. 5810–5817, 2004.