Exercise and the gut microbiome

Dr George Cho MFSc CEP ND
Clinic Director, Pathways Lifestyle Medicine Clinics
Medical Director, Lifestyle is Medicine
Certified Exercise Physiologist, Cleveland Clinic Canada

In 2017, four young rowers made an epic 5000 km trans-atlantic crossing from La Gomera in the Canary Islands to Antigua in the Caribbean. The four men, Sean Underwood, Eoin O’Farrell, Tommy Browne and Pat O’Connor were racing in the annual Talisker Whisky Atlantic Challenge in order to raise money for the pediatric department of Cork university hospital (1). But not only were they contributing to charity, they were contributing to science as well. Researchers from the hospital were tracking these athletes closely, particularly their stool (poo). The researchers collected the athletes’ fecal samples before the race, at the half-way point, at the end, and three months later. They did this in order to study the gut microbiome; a collection of trillions of bacteria, viruses, fungi, protozoa, archaea and parasites, living in the human gastrointestinal tract (2, 3). They wanted to know how exercise could influence the composition of the gut microbiome.  

What they found was amazing. First, they noticed that half-way through the race, the gut microbiome was more diverse than at the start of the race. This means there were more types of bacteria colonizing the gut during this expedition than at the start. What’s more interesting is that at the end of the race, the gut microbiome was even more diverse than at the half-way point, but intriguingly, when re-tested three months later, the diversity actually dropped. This meant that exercise was potentially having a diversifying effect on the gut microbiome.

But that is not all. When the researchers looked at which types of bacteria were increasing in number during the race, they noticed it was groups like the Roseburia hominis and members of the Subdoligranulum genus that had changed significantly (4). What makes these bacteria notable is that these bacteria are known butyrate producers. Butryate is short-chain fatty acid (SCFA) and is produced when gut bacteria metabolize (ferment) fibers from the food we eat. SCFA’s like butyrate have been shown to have amazing benefits to human health. For example, short chain fatty acids lowers pH (which can reduce the number of pathogenic bacteria) (5), helps regulate mood and emotions (6),  nourishes the cells lining our gut (colonocytes), and regulates whole-body immunity (ex. helps lower inflammation) (7).  SCFA’s are good for our health and the number of bacteria able to produce them was increasing with exercise. 

 But there is still more. They not only looked at the diversity of the bacteria themselves but also studied changes in metabolic genes of those bacteria (4). They did this to ascertain whether the changes in bacteria could influence changes in metabolism, and what they found was amazing. For key metabolic pathways like those involving certain essential amino acids, medium chain and long-chain fatty acids, 5-adenosyl L-methionine (SAMe) biosynthesis, fatty acid elongation and glycolysis, the abundance of genes was increased; meaning that the metabolic potential of those bacteria had increased. Note: Glycolysis is a major part of glucose (sugar) metabolism and SAMe is a precursor for glutathione (one of our body’s key antioxidants).  

Now why should we care? This little study in particular (though not perfect), sheds light on something that the scientific community has been noticing in general, which is that exercise changes the gut microbiome positively. Animal and human studies over the of the last several years have shown quite convincingly that exercise increases the diversity of the gut microbiome, increases the number of bacteria producing short-chain fatty acids, and increases the metabolic efficiency of the gut microbiome (8-14). All this helps our bodies because the trillions of bacteria in our gut have profound impacts on our health. They are essential for human metabolism, digestion and immune function (2,3,15). A diverse microbiome means a healthy gut. A healthy gut means a healthy immune system and a healthy immune system often translates to a healthy body.  

We all have heard that exercise is good for our health and the long list of benefits it provides. Scientists are now starting to add the gut microbiome as yet another positive benefit to this ever-growing list. Is it not high time for us to start taking exercise a little more seriously?  

Author

Dr George Cho CEP ND is a Naturopathic doctor who works at the Junction Lifestyle Medicine clinic and North York Lifestyle Medicine clinics in Toronto, Ontario, and serves as an advisor to Lifestyle is Medicine. He is also an Exercise Physiologist at Cleveland Clinic Canada. To learn more about his Naturopathic practice, visit the clinic website: https://www.pathwaystowholeness.ca.  

References 

1. The Talisker Whisky Atlantic Challenge: https://www.taliskerwhiskyatlanticchallenge.com/2017-leaderboard/

2. Cresci, G & Bawden, E. The Gut Microbiome: What we do and don’t know. Nutr Clin Pract. 2015 Dec; 30 (6): 734 – 746

3. Zhang, YJ et al. Impacts of gut bacteria on human health and disease. Int J Mole Sci. 2015 Apr; 16 (4): 7493 - 7519

4. Keohane, D et al. Four men in a boat: Ultra-endurance exercise alters the gut microbiome. J Sci med Sports. 22 (2019); 1059 – 1064

5. Conlon M & Bird A. The impact of diet and lifestyle on gut microbiota and human health. Nutrients 2015, 7, 17 – 44

6. Kelly J et al. Breaking down the barriers: the gut microbiome, intestinal permeability and stress—related psychiatric disorders. Frontiers in Cellular Neuroscience. 9:392

7. Singh R & Chang HW et al. Influence of diet on the gut microbiome and implications for human health. J Transl Med (2017) 15: 73 

8. Estaki, M et al. Cardiorespiratory fitness as a predictor of intestinal microbial diversity and distinct metagenomic functions. Microbiome (2016) 4: 42 

9. Scheiman, J., Luber, J et al. Meta-omics analysis of elite athletes identifies a performance-enhancing microbe that functions via lactate metabolism. Nature Medicine Vol 25 (2019): 1104 – 1109 

10. Petersen, L. Community characteristics of the gut microbiomes of competitive cyclists. Microbiome (2017); 5:98

11. Kern, T et al. Structured exercise alters the gut microbiota in humans with overweight and obesity – A randomized controlled trial. International Journal of Obesity. (2019)

12. Morita, E et al. Aerobic exercise training with brisk walking increases intestinal bacteroides in healthy elderly women. Nutrients. (2019), 11, 868; doi:10.3390/nu11040868

13. Mailing, L et al. Exercise and the gut microbiome: a review of the evidence, potential mechanisms, and implications for human health. Exercise and Sport Sciences Reviews.  (2019) 

14. Cook, M et al. Exercise and gut immune function: evidence of alterations in colon immune cell homeostasis and microbiome characteristics with exercise training. Immunology and Cell Biology (2015), 1 – 6

15. Cani, P & Delzenne N. The role of the gut microbiota in energy metabolism and metabolic disease. Current pharmaceutical design, 2009, 15, 1546 - 1558