Exercise Leads to Positive Change in the Microbiome
Effects of 9 weeks of intensity cycling 3–5 times a week
Intro:
So far, exercise was thought to enhance beneficial gut microbial species and improve the development of commensal bacteria, providing benefits to host health. It is even the parameter that most affects microbiota diversity according to Tim Spector in The Diet Myth.
Low intensity exercise can influence the gastrointestinal tract by reducing transit time, thus reducing the contact time between pathogens and the mucus layer. As a consequence, a regular sports practice could present protective effects against infection, colon cancer, diverticulosis and inflammatory bowel disease. However, prolonged or acute exercise can determine an increase of intestinal permeability, increasing risks of translocation and endotoxemia. As most things in life, the health benefits of exercise appear to be a question of balance.
What’s new?
In a recent study, 70 healthy college students who practiced less than one hour intensity training a week prior to the study went on to high intensity indoor cycling with three to five 1-hour sessions per week for 9 weeks.
17 of them gave fecal samples at the beginning and at the end of the protocol for microbiota analysis by sequencing the V3-V4 region of the 16S rRNA gene of Archae and Bacteria.
Results at taxa level
Significant differences were found in relative abundance between pre and post-training for several taxa:
- Actinobacteria, the group including Bifidobacteria, increased by about 3.4%
- Proteobacteria were reduced by from 7.6% to 2.2% with a large effect size (the normal healthy level for Proteobacteria is about 2.6%, and because this group includes many opportunistic pathogens, it is usually important for a healthy microbiome to keep it low)
- The Firmicutes/Bacteroidetes ratio increased with a moderate effect
- Verrucomicrobia, the group including Akkermansia muciniphila, showed a non-significant trend towards increase, and Fusobacteria, a group associating with colorectal cancer, was reduced, although non significantly.
Interestingly, the indexes of microbial diversity did not improve after exercise, contrarily to what was previously reported in the literature.
At genus level:
123 genera comparisons were analysed and 29 appeared to have evolved by over 1%. Here are the ones most interpretable:
- Bifidobacteria went from an average of 0.37 to 2.33%. With Bifidobacteria considered as probiotic genus and a guardian of gut balance thanks to an important anti-inflammatory activity and a protective effect against gut permeability, this outcome can be considered positive. In addition, Bifidobacteria are lactate producers, which through cross-feeding often leads to optimized butyrate production, a key health parameter for enterocytes health.
- Escherichia and Sutterella were reduced, an outcome considered positive as these genera include opportunistic pathogens
- Blautia, a bacterium considered as eubiotic (good) tended to increase. This is a short-chain fatty acids producer, which associates with reduced inflammation, insulin resistance and obesity.
- Akkermansia went from 0 to 0.07%, a difference that is non-significant, although it had been reported as among the most responsive to endurance training in a study in overweight women.
Confounders & benefits
The 9 weeks training led to an average of 20% reduction in fat mass and 3.7% gain in muscle mass, together with an increase in power.
The diet was controlled all through the study duration, and the researchers found the training to promote healthier food choices, with an increase in protein intake by 16%, carbs by 23%, as well as fiber and vitamin C, suggesting a higher consumption of fruits and vegetables compared to prior to the study.
This is a confounding factor in relation to the modifications occurring in the microbiota: are these changes really due to the physical activity, or to evolutions in diet? Although it is difficult to answer this question based on this study, it also is important to consider that physical activity, diet and microbiome are all inter-related.
An increase in fiber intake leads to more short chain fatty acids produced in the gut, which mediate the cross-talk between the microbiota and the muscles. Short chain fatty acids stimulate glucose uptake and deposition of proteins in skeletal muscle tissue, while keeping in check inflammation and gastrointestinal disorders.
To conclude
The mutual interactions between these parameters are at the heart of a healthy lifestyle, and maybe it is even more arduous to separate them in our daily life than it is in the laboratory. After all, everything is interdependent. #OneHealth.
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