How sport protects us from disease

In a Germany-wide survey, about 45% of respondents said they rarely or never exercise. Yet we are all too aware that physical activity is actually essential for our health. We know that exercise strengthens our cardiovascular system as well as our immune system. It protects us from broken bones, reduces dangerous visceral fat, and offers numerous other benefits. But there’s another part of our body that benefits from regular exercise and rewards us in return: our gut microbiome!

Exercise Against Cancer Risks

The protective effect of exercise against disease is evident, for example, in the risk figures for colorectal cancer, also known as bowel cancer. Active people have a 24% lower risk of developing the disease. Although the exact mechanism behind this is not fully understood, our gut bacteria appear to play a role. This is supported by the fact that the composition of the gut microbiome in people with the disease differs from that in healthy individuals. To understand how this relates to exercise, let’s first take a general look at the relationship between physical activity and our gut bacteria.

Exercise Alters Our Gut Microbiome

The stated goal of many researchers is to influence the gut microbiome and, by extension, our health. Our diet is arguably the biggest and most important factor in this—but by no means the only one. Exercise also has an impact on the composition of our microbiome.

Athletes, such as marathon runners, have a more diverse microbiome compared to people who engage in little or no physical activity. In particular, athletes have more species that produce what are known as “short-chain fatty acids.” These acids break down dietary fiber—which our bodies cannot digest on their own—making it accessible to our bodies. These short-chain fatty acids are extremely valuable because they not only supply our body and brain cells with energy but also have anti-inflammatory effects, among other functions.

Bacteria Can Protect Us from Bowel Cancer

The protective effect of exercise against colorectal cancer may be linked to increased production of short-chain fatty acids, particularly butyrate. Regular physical activity increases the proportion of bacterial species that produce butyrate. In contrast, studies show that colorectal cancer patients have lower concentrations of butyrate-producing bacterial species.

In in vitro studies, healthy epithelial cells—that is, body cells found in the intestine—react differently to butyrate than diseased tumor epithelial cells. In healthy cells, butyrate is metabolized, leading to the activation of genes that promote cell growth. This results in a strong intestinal wall that protects our body from harmful substances in food. Tumor cells, on the other hand, cannot break down butyrate; they accumulate it inside the cell, thereby inhibiting cell growth. The cell dies, and the tumor shrinks.

Mice particularly susceptible to this type of cancer developed smaller tumors through regular exercise, and a correlation was observed between their butyrate concentration and the number of tumors.

Despite promising results from experiments, it is important to note that laboratory data are not always directly applicable to humans. Nevertheless, there is strong evidence to suggest that exercise and the resulting changes in the gut microbiome have a protective effect against colorectal cancer.

Protection for Nerve Cells

One of the most important neurotransmitters in our brain is the so-called “brain-derived neurotrophic factor” (BDNF), which protects our nerve cells from dying. In experiments with mice, a deficiency in BDNF led to the death of nerve cells in the brain. Interestingly, there is a link between low BDNF levels and anxiety disorders as well as depression, often in connection with inflammatory bowel diseases.

The fact that BDNF levels are linked to our bacteria is evident in germ-free mice that have never come into contact with bacteria. Compared to non-germ-free animals, these mice exhibited lower BDNF concentrations in brain regions such as the hippocampus and parts of the cortex. It was also demonstrated that the administration of bifidobacteria leads to an increase in BDNF levels.

Experiments with piglets also showed that exercise led to a higher proportion of bifidobacteria. The elimination of these bacteria through antibiotics resulted in delayed cell growth in the hippocampus. This delay, in turn, could be reversed by the administration of bifidobacteria as well as through exercise training.

This shows that physical activity alters the microbiome and thereby has a positive effect on our brain and mental state.

Holistic Health Through Sports

There is a direct link between exercise, gut bacteria, and our health. A holistic perspective is essential. Exercise supports our bodies in the complex interplay between bacteria and body cells, thereby protecting us from disease. (LS)

Further reading:

Mailing LJ, Allen JM, Buford TW, Fields CJ, Woods JA. Exercise and the Gut Microbiome: A Review of the Evidence, Potential Mechanisms, and Implications for Human Health. Exerc Sport Sci Rev. April 2019;47(2):75-85. doi: 10.1249/JES.0000000000000183.

Dalton A, Mermier C, Zuhl M. The influence of exercise on the microbiome-gut-brain axis. Gut Microbes. 2019;10(5):555-568. doi: 10.1080/19490976.2018.1562268.

Clauss M, Gérard P, Mosca A, Leclerc M. Interplay Between Exercise and the Gut Microbiome in the Context of Human Health and Performance. Front Nutr. June 10, 2021;8:637010. doi: 10.3389/fnut.2021.637010.