Exercise and gut flora diversity are positively correlated

Being physically fit appears to be associated with a greater diversity of gut bugs, researchers found.

In a case-control study, Irish athletes had a far wider range of intestinal microbes than did matched controls who weren't athletes, Fergus Shanahan, MD, of the University College Cork in Ireland, and colleagues reported online in Gut.

"Exercise seems to be another important factor in the relationship between the microbiota, host immunity, and host metabolism, with diet playing an important role," they wrote.

There's been much attention surrounding gut microbiota and its relationship with obesity and metabolism, but few have looked specifically at the effects of exercise on these gut microbes.

Shanahan and colleagues looked at 40 professional athletes from an international rugby team while they participated in pre-season camp -- a regulated environment -- and compared them with healthy male controls from the Cork region of Ireland.

They found that athletes and controls differed with respect to plasma creatinine kinase, a marker of extreme exercise, and inflammatory and metabolic markers. Athletes had less inflammation and better metabolism than did controls, they reported.

Athletes also had a far higher diversity of gut bugs -- 22 phyla, 68 families, and 113 genera compared with just 11 phyla, 33 families and 65 genera for controls with a low body mass index (BMI), and 9 phyla, 33 families and 61 genera for controls with a high BMI.

Athletes also consumed far more protein than controls, with protein accounting for 22% of their total energy intake compared with 16% of energy intake for low-BMI controls and 15% for high-BMI controls.

This high protein intake, as well as high levels of creatinine kinase, positively correlated with bacterial diversity, suggesting that both diet and exercise are drivers of biodiversity in the gut, Shanahan and colleagues wrote.

The results provide evidence that exercise has a beneficial effect on gut microbiota diversity, they concluded, but it also indicates that the relationship is complex since it's also tied to dietary extremes -- which is why further investigation is needed into the relationship, with a particular need for intervention-based studies to tease it apart.

In an accompanying editorial, Georgina Hold, MD, of the University of Aberdeen in Scotland, noted that the article is the first to report that exercise increases gut microbe diversity and that it "highlights that exercise is another important factor in the complex relationship among the host, host immunity, and the microbiota."

She added that future studies examining the impact of exercise and the nutritional value of foods in terms of relevance to gut bacteria are essential: "Developing new ways to manipulate the beneficial properties of our microbiota by finding ways to integrate health-promoting properties into modern living should be the goal."