Exercise is well known to support both body and mind, but new research suggests how hard you train could also affect your gut.
A study from Edith Cowan University in Australia looked at athletes under different training loads and found that gut health markers shifted with exercise intensity. When athletes trained harder, their gut microbiome showed changes in bacteria and short-chain fatty acids, compounds linked to digestion and overall health.
One possible explanation involves lactate, the byproduct of intense exercise. Researchers note that lactate produced in muscles can move to the gut, where it may fuel changes in bacterial populations.
But training intensity wasn’t the only factor. During lighter training periods or rest days, athletes’ diets tended to slip: more processed foods, fewer fruits and vegetables, and a moderate rise in alcohol intake. Even though total carbs and fiber stayed the same, this drop in diet quality also altered the gut microbiome. Gut transit time, the speed at which food moves through the digestive system, also slowed during these lower activity periods, another shift linked to gut changes.
“While it's still unclear exactly how the gut influences athletic performance, there are some promising clues,” said study author Bronwen Charlesson, a PhD candidate at Edith Cowan University. “For example, the gut may play a role in lactate metabolism and regulating pH levels, both of which could impact performance and overall athlete health. However, more research is needed, particularly into factors like training load, diet quality and gut transit time, to better understand how these elements can be adjusted to enhance athletic performance.”
This research, published in the Journal of the International Society of Sports Nutrition, was supported by Edith Cowan University and completed as part of a PhD scholarship with the Western Australian Institute of Sport.