The positive effects of exercise have been well documented. Physical activity wards off obesity, heart disease, diabetes, and it ensures a host of other bodily functions work properly. Now, a team from the University of Colorado-Boulder believes we can add the digestive system's microbial community to that list.

Their research, published in the journal Immunology and Cell Biology, suggests exercising early in life can alter gut microbes for the better. Researchers found exercise during a window of opportunity in early-life helps optimize health by promoting better brain and metabolic activity. "Exercise affects many aspects of health, both metabolic and mental, and people are only now starting to look at the plasticity of these gut microbes," said senior study author Monika Fleshner, a professor in CU-Boulder's Department of Integrative Physiology, in a press release. "That is one of the novel aspects of this research."

The human gut is teeming with trillions of microorganisms, which take up residence in the intestines just after birth. These organisms are critical to the development of the immune system and several neural functions, and are capable of adding up to 5 million genes to a person's genetic profile. Experts look to the gut as "a tremendous influence on human physiology."

Though the microbial community is considered somewhat malleable into adult life, including being susceptible to changes in sleep and diet patterns, the researchers saw that gut microorganisms are at "peak plasticity" at a young age. By using rats as a model, the team could see rodents who exercised every day as juveniles developed a more beneficial microbial structure. This included the expansion of important probiotic bacteria compared to their sedentary counterparts, as well as rats exercising only in adulthood.

The researchers have not yet pinpointed a precise age at which the gut microbe community is most susceptible to change, but these preliminary findings seem to indicate the earlier, the better.

Fleshner explained that a healthy, robust microbe community appears to promote healthy brain function, even providing antidepressant effects. Previous research on the topic has indicated that the human brain responds to microbial signals from the intestine — the exact communication methods of which remain unclear.

"Future research on this microbial ecosystem will hone in on how these microbes influence brain function in a long-lasting way," said lead study author Agnieszka Mika, a graduate student in CU-Boulder's Department of Integrative Physiology.

To build upon these findings, researchers plan to look at possible means of encouraging positive gut microbe plasticity in adults whose intestinal communities are more resistant to change.

Source: Mika A, Fleshner M. Early life exercise may promote lasting brain and metabolic health through gut bacterial metabolites. Immunology and Cell Biology. 2015.