In recent years, there has been an explosion of interest in the role that gut microbes play in health. A multitude of studies have shown that people with large and diverse germ populations in their digestive tracts tend to be less prone to obesity, immune problems and other disorders than people with low microbial diversity, and that certain germs may contribute to improved metabolic and immune health.
But little science had examined the interplay between physical activity and gut bugs. So, for a study published this month in Gut, researchers at University College Cork, part of the National University of Ireland, and other institutions, set out to learn more by turning to a group of people who exercise a lot: the national rugby team of Ireland.
We chose professional athletes as a study group, because we wanted to be sure not to miss any effect of exercise and needed a group who were safely performing at the extremes of human endeavour, said Dr Fergus Shanahan, an author of the study who is a professor of gastroenterology and director of the Alimentary Pharmabiotic Center at University College Cork.
Forty players agreed to participate. At the time of the study, they were exercising strenuously every day.
For comparison, the researchers also recruited two groups of healthy adult men, none of them athletes. One group consisted of men with a normal body mass index. Most in this group exercised occasionally.
The men in the final group were generally sedentary and had a body mass index that would qualify them as overweight or obese. This group was included, Dr. Shanahan said, because the rugby players, although supremely fit, were physically huge.
The scientists collected blood and stool samples from all the men. The volunteers also completed questionnaires about their exercise routines and diet, and spoke with a nutritionist about their daily food intake.
Then the scientists analysed the mens blood for markers of muscle damage and inflammation, which would indicate how much each volunteer had or had not been moving and exercising recently. The scientists also used sophisticated genetic sequencing techniques to identify and enumerate the particular microbes living in each mans gut.
As it turned out, the internal world of the athletes was quite different from that of the men in either of the control groups. The rugby players had considerably more diversity in the make-up of their gut microbiomes, than did those of the other men.
The rugby players guts also harbored larger numbers of a particular bacterium, Akkermansiaceae, that has been linked in past studies with a decreased risk for obesity and systemic inflammation.
The men in both of the control groups, on the other hand, especially those with the highest BMIs and who rarely exercised, had relatively low numbers of Akkermansiaceae in their guts and elevated markers for inflammation in their bloodstreams.
- GRETCHEN REYNOLDS