Professional athletes are big winners when it comes to their gut microflora, suggesting a beneficial effect of exercise on gastrointestinal health, investigators report in an articlepublished online June 9 in Gut.

DNA sequencing of fecal samples from players in an international rugby union team showed considerably greater diversity of gut bacteria than samples from people who are more sedentary.

Having a gut populated with myriad species of bacteria is thought by nutritionists and gastroenterologic researchers to be a sign of good health. Conversely, the guts of obese people have consistently been found to contain fewer species of bacteria, note Siobhan F. Clarke, PhD, from the Teagasc Food Research Centre, Moorepark, Fermoy; Alimentary Pharmabiotic Centre, University College Cork; Microbiology Department, University College Cork; and Alimentary Health Ltd, Cork, Ireland, and colleagues.

“Our findings show that a combination of exercise and diet impacts on gut microbial diversity. In particular, the enhanced diversity of the microbiota correlates with exercise and dietary protein consumption in the athlete group,” the authors write.

The investigators used 16S ribosomal RNA amplicon sequencing to evaluate stool and blood samples from 40 male elite professional rugby players (mean age, 29 years) and 46 healthy age-matched control participants. The researchers evenly divided control participants between those with a low body mass index (BMI), defined as a BMI of 25 kg/m² or less, and those with a high BMI (>28 kg/m²). Participants also filled out food and exercise questionnaires.

Relative to control participants with a high BMI, athletes and control participants with a low BMI had improved metabolic markers. In addition, although athletes had significantly increased levels of creatine kinase, they also had overall lower levels of inflammatory markers than either of the control groups.

Athletes were also found to have more diverse gut microbiota than controls, with organisms in approximately 22 different phyla, 68 families, and 113 genera. Participants with a low BMI were colonized by organisms in just 11 phyla, 33 families, and 65 genera, and participants with a high BMI had even fewer organisms in only 9 phyla, 33 families, and 61 genera.

The professional rugby players, as the investigators expected, had significantly higher levels of total energy intake than the control participants, with protein accounting for 22% of their total intake compared with 16% for control participants with a low BMI and 15% for control participants with a high BMI.

When the authors looked for correlations between health parameters and diet with various microbes or microbial diversity, they found significant positive association between microbial diversity and protein intake, creatine kinase levels, and urea.

“The article is the first report that exercise increases gut microbiota richness/diversity and highlights that exercise is another important factor in the complex relationship among the host, host immunity and the microbiota,” Georgina L. Hold, PhD, from the Institute of Medical Sciences at the University of Aberdeen, Scotland, writes in an accompanying commentary.

“The fact remains though that our gut microbiota is not programmed to keep pace with the demands that modern life throws at us. Research focused on sustaining health rather than restoring health is urgently needed. Understanding the impact of exercise and the nutritional value of foods in terms of relevance to our microbiota is essential,” she concludes.

The study was funded by a Science Foundation Ireland award to the Alimentary Pharmabiotic Centre at University College Cork. Dr. Clarke is supported by a Teagasc Walsh fellowship. Research in the laboratory of a coauthor is supported by a SFI Principal Investigator award. The other authors and Dr. Hold have disclosed no relevant financial relationships.

Gut. Published online June 9, 2014. Article abstract, Comm