Exploring the vital connection between gut microbes, physical activity, and health

Our bowels accommodate billions of active microbes that affect the health, a fact that is arousing increasing interest also among athletes. For example, performance-enhancing intestinal microbe populations have been found in athletes participating in endurance sports. There is also research evidence for the notion that physical activity produces health-promoting changes in the bowels.

Sanna Lensu is interested in the functioning of the gut–brain axis that connects gut microbes and the nervous system. Image Credit: University of Jyväskylä

Gut microbes have kept Academy of Finland Research Fellow and sports medicine specialist Satu Pekkala busy for ten years already. In Jyväskylä, she and her colleague Postdoctoral Researcher Sanna Lensu have studied the vital connection between microbes and health.

Researchers’ attentive work brings great benefit to athletes – and evidence for this benefit is increasing all the time: the right kind of gut microbes keep an athlete healthier, and some microbes can even improve athletes’ performance capacity.

“However, in the realm of sport, insights on the connections between food and gut microbes remain limited,” says Satu Pekkala, whose research belongs to the field of sports medicine.

She continues: “In human biology, the gut microbes include not only bacteria but also bacteriophages, other viruses, yeasts, and parasites. One’s gut microbiome is partly inherited, but one can modify it by lifestyle choices. On the level of bacterial families, the intestinal microbiome is fairly well-known already.

“Normal bowels behave so that the gut microbiome is restored after a course of antibiotics, for example. However, it is not restored after an inflammatory bowel disease, such as Crohn’s disease. Such diseases have become more frequent in the population.”

In the guts, microbes break up nutrients and produce as their metabolic outcomes various substances, many of which promote human health:

1. Microbes produce, for example, neurotransmitters that affect both the guts and the brain. They are known to regulate satisfaction and mood in the central nervous system.
2. Microbes also produce vitamins that are important for the human body.
3. A beneficial microbiome also prevents inflammatory states both in the guts and elsewhere in the body.
4. Gut microbes also contribute to protection against pathogens.

In diseased situation dysbiosis of gut microbes is harmful for the health and it e.g. increases the inflammation.

There is already good evidence about the positive effect of physical activity on bowel functions

According to the researchers, there is already good evidence from cross-sectional studies about the connection between athletes’ microbiome and performance capacity. Last year, Pekkala and Lensu published review articles about these results in, among others, the Duodecim medical journal.

The connection has especially been studied for endurance sports, but to date there is much less knowledge related to other forms of physical exercise, such as the effects of strength training.

Physical activity both diversifies the gut microbiome and increases performance-enhancing microbes in athletes’ bowels. Interesting findings in view of performance have been made, for example, regarding the intestinal microbiome of top athletes:

”In one study, top athletes had more of health-promoting Akkermansia bacteria,” Pekkala says. “In addition, endurance exercise has been shown to increase the volumes of Akkermansia and health-promoting fecal bacteria.”

Moreover, there is research evidence that the abundance of Veillonella bacteria increased in marathon runners’ bowels after the performance. These bacteria break up lactate produced while performing and thereby increase the athlete’s performance capacity.

Soon we will also acquire new evidence about the connection between gut microbiome and top athletes’ success.

We have examined 27 national top athletes and a control group. We observed interesting differences in terms of the microbe families, which were further associated with health-promoting blood values.”

Satu Pekkala, Academy of Finland Research Fellow

In March, Pekkala and her research team sent an article describing these findings for peer review. The team includes researchers from the Faculty of Sport and Health Sciences, the Research Institute for Olympic Sports (KIHU), and Turku University Hospital.

The effects of beneficial microbes end if physical activity ends

The effects of physical activity on GM are short in duration, however. When physical activity discontinues, the related favorable changes in gut microbiome soon fade. This happened, for example, in one study regarding the abundance of fecal bacteria and short-chain fatty acids produced by microbes. These fatty acids have positive effects on metabolism, for instance, as well as anti-inflammatory effects.

Research evidence about the connection between physical activity and gut microbes has also been gathered from tests with rats, explains animal physiologist-toxicologist Sanna Lensu, who is currently working on brain research at the Department of Psychology, University of Jyväskylä.

“We have used the rat model that are selectively bred into good or poor runners,” Lensu says. “The good runners are metabolically healthier than the poor runners. Fecal transplantation, that is, the transmission of the entire gut microbiome from the good runners into the poor ones, made the poor runners run voluntarily more, but unfortunately the effect of a single transplant lasted for only a rather short time. More analyses are forthcoming, and they will be part of Elina Mäkinen’s doctoral dissertation.”

Lensu is particularly interested in the functioning of the gut–brain axis that connects gut microbes and the nervous system.

At present, she is waiting for further findings from the rat studies. What happens in the rats’ brains after the rats have been running and they have received a fecal transplant? The issue has been studied by means of tissue samples and behavioral tests.

“It seems that in addition to voluntary mobility, the fecal transplantation influences behavior as well, and it will be interesting to see the results of the final microbe and brain analyses,” Lensu says.

Physical activity and gut microbes to be included in national population studies

The connection between the effects of moderate physical exercise and gut microbes has not yet been studied to any large extent in ordinary healthy citizens.

“For example, from the large national research data of the FINRISKI study, researchers have already investigated the connections of microbiome to fatty liver and mortality rates,” Lensu says. “The data also include information on the subjects’ physical activity and fitness, but we are still waiting for research publications regarding the connections between microbes and physical activity.”

People make plenty of high-standard population studies and collect excellent datasets in Finland. Therefore, the researchers hope that in the future the large national population studies would enable collecting data also on people’s gut microbes and physical activity.

“Longitudinal sampling, in particular, requires plenty of research investments and resources, which also calls for positive attitudes from those funding research,” Lensu states.

Fiber-rich food is fundamental to good intestinal condition

Anyone can start improving the composition of his or her gut microbiome. The key to this is a well-rounded diet, especially fiber-containing food. Fiber-rich food diversifies the gut microbiome and increases the abundance of beneficial microbes.

What impacts do fibers have in the guts or what is the influential mechanism therein?

“Beneficial microbes like fibers in food,” Pekkala says. “While processing the fibers, the microbes produce short-chained fatty acids and promote, for example, glucose metabolism. In addition, these microbes decrease inflammatory state in the guts and elsewhere in the body, which may contribute to a lower risk of metabolic diseases.”

The researchers have good pieces of advice as to how one can increase the proportion of fiber in one’s diet.

“For children, good advice is that parents should offer a plate at each meal with plant products of five different colors, and preferably fresh, meaning, as little processed as possible.”

Sanna Lensu, Postdoctoral Researcher, University of Jyväskylä

Energy bars, fast food and sweets contain lots of harmful additives

Alongside food and physical activity, the condition of the microbiome benefits from sufficient sleep and contact with microbes in natural surroundings. According to research findings, harmful things for the microbiome include, for example, stress, smoking, alcohol, sugar, saturated fats and proteins of animal origin as well as some drugs.

“For example, the small beneficial impacts of strength exercise on gut microbes may be related to the fact that abundant supply of protein and especially the eating of red meat is not beneficial to the microbes.”

Sanna Lensu, Postdoctoral Researcher, University of Jyväskylä

The researchers also point out the adverse side of the current culture of fast food, snacks and protein bars, which has become more common among both athletes and ordinary physically active people.

“Energy and recovery food products contain various additives that are harmful to the intestinal microbiome and thereby to human health,” Lensu says.

“Many people eat added protein, even though they would not need to, and the extra protein cumulates as fat in the body and also as urine nitrogen in wastewater and from there to the environment. In addition, protein bars often contain undesirable fats and a lot of energy. The energy content takes you a long way as such, but you will soon feel hungry again.”

”According to a recently published randomized study, carboxymethylcellulose (E466), which is used as a thickening agent, reduced the diversity of microbiome as well as short-chained fatty acids,” Pekkala says.

“At the same time, it increased intestinal inflammation and gut pains. In addition, tests with mice have shown that E466 increased anxiety and eating disorders. This additive is used in energy food products as well as in ice cream, pastry, and convenience food products, for instance.”