The mind and body benefits of exercise are well-known. Research points to a possible mechanism for some of these effects: Physical exercise may change the composition of the microbiome, which refers to the trillions of microscopic bacteria that reside in our guts.

In prior studies, mice receiving bacterial transplants from animals that had exercised showed greater resistance to tissue damage and greater ability to fight inflammation, which may improve brain and body health.

To follow up on the animal experiments, researchers from the University of Illinois at Urbana-Champaign studied 32 human volunteers whose microbiome was assessed after six weeks of regular workouts. The volunteers started at approximately 30 minutes of daily walking and then advanced to more vigorous workouts of about an hour of jogging or cycling three times a week.

The volunteers’ microbiomes showed increases in microbes that produce fatty acids which reduce inflammation throughout the body. These benefits went away after the volunteers stopped exercising regularly.