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.
Photo: Canna, Xavier La. "Gut Organisms Could Be Key to Unlocking Western Diseases." ABC News. N.p., 24 Oct. 2014. Web. 02 Apr. 2017.
Obesity is a major health concern. Nowadays, more than 500 million people are obese worldwide leading to considerable economical costs as well as public health challenge. Obesity arises from complex interactions between genes and environmental factors such as diet, food components and/or way of life, and results from a long-term positive imbalance between energy intake and expenditure with excessive increase in body fat (1).
Gastrointestinal disorders resulting from obesity are more frequent and present earlier than type 2 diabetes and cardiovascular diseases. Diseases such as gastroesophageal reflux disease (GERD is a digestive disorder that affects the lower esophageal sphincter which causes heartburn or acid indigestion), cholelithiasis (involves the presence of gallstones that form in the biliary tract, usually in the gallbladder), and non-alcoholic steatohepatitis (liver inflammation and damage caused by a buildup of fat in the liver) are directly related to body weight and abdominal adiposity (2). There is growing evidence that the gut microbiota (bacteria harbouring the gut) and its bacterial genome (the complete set of genes or genetic material present in the bacteria) affect how much of the food we eat are absorbed by the body, energy regulation and fat storage. These findings raise the possibility that the gut microbiota plays a role in regulating host energy metabolism and may contribute towards the development of obesity and associated metabolic diseases.
Adult humans are colonized by microbes from nine divisions (deep evolutionary lineages) of Bacteria and at least one division of Archaea (1). Moreover, three bacterial divisions, the Firmicutes, Bacteroidetes and Actinobacteria (a different type of microbe), dominate the adult human gut microbiota (bacteria that harbours the gut) and account for more than 90 % of all bacteria, whereas Methanobrevibacter smithii, a hydrogen-consuming methanogen (microbes that produce methane), dominates the Archaea domain.
Studies have shown that obese mice as well as humans had different gut microbiota composition compared to lean. A number of studies showed an increase in bacteria from the Firmicutes phyla and a decrease in the Bacteroidetes phyla that is believed to be associated with increased energy absorption from food and increased low-grade inflammation (3). Moreover, other experiments suggest that obesity can influence the composition of gut microbiota. For example, when obese people diet and lose weight, the proportion of Bacteroidetes increases relative to Firmicutes. Bacteria from the firmicutes phyla of bacteria extract short chain fatty acids from dietary fiber at higher rates than other gut microbes. The result is the person harboring more of these microbes gains an extra 150 calories daily. An imbalanced gut ecosystem can cause inflammation throughout the body that slows down the body’s metabolism, induces insulin resistance and leads to fat accumulation (4)
What can you do (4)?
1. Gérard, Philippe. "Gut Microbiota and Obesity." Cellular and Molecular Life Sciences 73.1 (2015): 147-62.
2. Acosta, Andres, and Michael Camilleri. "Gastrointestinal Morbidity in Obesity." Annals of the New York Academy of Sciences 1311.1 (2014): 42-56.
3. Ley, Ruth E., Peter J. Turnbaugh, Samuel Klein, and Jeffrey I. Gordon. "Microbial Ecology: Human Gut Microbes Associated with Obesity." Nature 444.7122 (2006): 1022-023.
4. John, George Kunnackal, and Gerard E. Mullin. "The Gut Microbiome and Obesity." Current Oncology Reports18.7 (2016): n. pag.