New Exercise Perk: Healthier Gut Bacteria

Exercise is good for the heart, lungs and mind, and now we can add gut bacteria to the list, a new study from Ireland suggests.

Researchers looked at professional rugby players and found that these elite athletes had a more diverse collection of bacteria in their digestive systems than other healthy men, who were not athletes, but were of similar age and body size.

"The most important aspect of our study is that it draws attention to the possibility that exercise may have a beneficial effect on the microbiota colonizing the human body, and it is associated with a more diverse microbiota," said study researcher Dr. Fergus Shanahan, a gastroenterologist and professor of medicine at University College Cork in Ireland. 

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There is a growing body of scientific evidence suggesting that the trillions of bacteria and other microbes living in the digestive tract play an important role in both digestive health and overall health. Greater microbial diversity has generally been linked with better health in older adults, while a loss of diversity has been observed in people with conditions as wide ranging as obesity, inflammatory bowel disease and autism, the researchers said. [5 Ways Gut Bacteria Affect Your Health]

The findings are published online today (June 9) in the journal Gut.

Increased microbial diversity

In the study, the researchers analyzed blood and stool samples from 40 Irish rugby players who were attending their team's preseason training camp, as well as from 46 young Irish men who formed two comparison groups. One comparison group was made up of men who had a body mass index (BMI) in the normal range, of 25 or less, and were generally fit (but didn't exercise as much as the athletes); the other group of men were overweight or obese, with a BMI of 28 or more, and were less fit.

The analysis revealed that rugby players had greater diversity of gut bacteria than men in either of the two comparison groups, and the athletes also had higher levels of the types of bacteria linked with better health. 

The men were asked to report their food intake from the previous month, and the researchers found that rugby players ate more calories, fruits and vegetables, fat and protein, which was typically consumed as meat or protein supplements. 

Protein represented 22 percent of the athletes' total calories, but only 15 to 16 percent of the comparison groups'. The findings also suggested that protein intake appeared to be linked with a greater degree of microbial diversity, the researchers said.

Lifestyle affects gut microbes

"We don't know for certain if it is the exercise per se, or the dietary changes accompanying exercise that mediate the change in microbial diversity," Shanahan said. "It may have been the combination."

To tease apart the effects of the two, further research is under way. Although the exact mechanism remains unclear, Shanahan says he suspects both diet and exercise have a positive influence on microbial diversity, which in turn boosts the immune system while preventing the body's inflammatory response from becoming overactive.

The amount of exercise needed to enhance gut bacteria is also not known, the researchers said. But it's clear from the study that people do not need to be professional athletes to see some of the benefits, and that being moderately active helps. Although the findings showed that rugby players had the widest range of gut microbes, the fitter comparison group also had broader microbial diversity than the less active men.

Shanahan said his new research hopes to distinguish the effects of exercise alone on microbial diversity, from those accompanying dietary changes. This study is looking at nonathletes and measuring their gut microbes before and after a structured exercise program in which their dietary intake is being controlled and monitored, he explained.

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