May 11, 2017
By: Anna Pashkova, ACSM EP-C
The gut microbiota and microbiome have been growing topics in the research field over the last several years with large role they play in both health and disease. It is estimated that we have trillions of diverse microorganisms living in our gut. Within these organisms, it is estimated that about 1,000-1,150 different bacterial species exist. While the microbiota refers to the microorganisms in our gut, the microbiome refers to the genome of the microorganisms, which is estimated to be 150 times greater than the human genome. Because of this, there is still much to learn about the gut microbiota.
We do know factors that affect the gut microbiota include diet, medications, stress, birthing process, infant feeding methods, age, and geographical location. One example of the well-known impact that diet has on our microbiota is through the consumption of prebiotics and probiotics. A well-balanced microbiota is essential for our body to process nutrients in our food and plays a large role in the immune system, which affects health and disease in many ways.
A normal gut microbiota is in symbiosis, or living in compatibility with us, while a disrupted microbiota is known to be in dysbiosis. Dysbiosis can lead to inflammatory diseases that can develop into symptoms outside of the gut including allergy and asthma, obesity and diabetes and hypertension. Inflammatory bowel disease and colorectal cancer can develop within the gut. Because of this, it is vital that we aim to keep our gut microbiota healthy and living in symbiosis with us.
Exercise and Gut Bacteria
Researchers are beginning to explore the impact of exercise on the gut microbiota. According to this review, exercise seems to impact gut microbial composition both in number and quality of microbes with potential health benefits for the host and may even have the potential to increase exercise performance. Most of the research has been conducted in mice and rats with both voluntary and controlled exercise studies, although several human studies have recently appeared.
Image source: The microbiota: an exercise immunology perspective
Animal Research
Matsumoto et al. (2008): Rats who voluntarily ran more had increased n-butyrate concentrations and increased cecum diameters. Butyrate is produced by gut microbiota through fermentation of carbohydrates and protects against colon cancer and IBD.
Evans et al. (2014): Mice were fed high-fat diets to induce obesity and combined with running as an exercise. The distance ran by rats inversely correlated with Bacteroidetes:Firmicutes ratios. Lower levels of Bacteroidetes and higher levels of Firmicutes have been seen in genetically obese mice and in the fecal microbiota of obese humans compared to lean controls. This showed that exercise may prevent diet-induced obesity and produced microbial compositions similar to lean mice.
Campbell et al. (2016): This study found that exercise helped develop a unique microbiome independent of diet (normal diet vs. high fat diet) and suggested that the exercised mice had more digestive tract protecting bacteria in mice.
Mika et al. (2015): This study found that exercise during early life influences microbiota composition in rats and favors health-enhancing microbial species that are optimal for brain function. This study suggested that the impact of exercise on gut microbiota may be dependent on time of initiation during the life span.
Cook et al. (2015): This study revealed that exercise has an anti-inflammatory role in the gut, and emerging data shows various forms of exercise training may impact severity of intestinal inflammation during inflammatory insults, such as in ulcerative colitis. Different forms of exercise may also be related to gut immune cell homeostasis and microbiota-immune interactions, but more research is needed.
Human Research
Clarke et al. (2014): This study compared the microbiome of professional rugby athletes to age-matched sedentary counterparts. The athletes had greater microbe diversity in fecal samples compared to sedentary individuals. This study was cross-sectional and lacked control of dietary and other factors that may have influenced the outcome, but showed that exercise and microbial diversity may be correlated.
Estaki et al. (2016): This study demonstrated peak oxygen uptake (gold standard of cardiorespiratory fitness) can account for more than 20% of microbial diversity after accounting for all other factors including diet and fecal butyrate production was higher in physically fit participants, which also had higher amounts of butyrate-producing taxa of bacteria. This authors of this study suggest the use of exercise prescription as an adjuvant therapy for dysbiosis-associated diseases.
Bressa et al. (2017): This study compared women with active lifestyles versus women with sedentary lifestyles and found higher abundance of health-promoting bacteria species in the active women. Active was defined as participating in the minimum amount of exercise recommended by the World Health Organization. The active women also ate more fruits, vegetables and fiber-rich foods than the sedentary women.
In Summary
Overall, exercise seems to be related to an increase in the number of beneficial microbial species and enriched diversity to support a healthy gut microbiota, but research in this area is still in the early stages. Additionally, it is difficult to distinguish the effect of exercise alone, as diet and other factors may play significant role in gut health.
Regardless, exercise has plenty of other health benefits including decreasing the risk of heart disease, high blood pressure stroke, diabetes, osteoporosis, and certain cancers. It can also help control stress, improve sleep, boost mood, control weight, and reduce risk of falling and improve cognitive function in older adults. It will be interesting to see if future research can provide more evidence.
The take-home message? Choose to enjoy physical activity regularly and you’ll enjoy numerous health benefits! Plus, physical activity is fun - just remember to fuel your body with nutritious food, too!