You exercise for heart health, lean muscle strengthening, fat loss and happy hormones. Now it turns out that all those workouts may also benefit your gut bacteria -- a (hopefully) diverse ecosystem of trillions of microorganisms that live in your intestines and help keep your digestive system running smoothly.
Thus far, most research on gut bacteria has focused on how to eat your way to a diverse microbiome, but a recent novel study from University College Cork demonstrates that it isn't just what you put into your body as fuel -- exercise may have an effect on gut bacteria.
The study, published online in the journal Gut, found that professional athletes had better gut bacteria diversity than average people. A healthy and varied gut bacteria ecosystem has been linked to everything from low obesity rates to fewer symptoms of mental disorders like ADHD and anxiety, while non-diverse guts are associated with inflammation and markers of metabolic syndrome such as weight gain and insulin resistance.
Researchers, led by physician-scientist Fergus Shanahan, studied the blood and fecal matter of 40 professional rugby players who were rigorously training at the time. Then they compared those samples to the blood and fecal matter of a control group made up of 46 healthy men who were not athletes, but who roughly matched the rugby players' size and age.
The control group was also divided into two parts: men with a normal body mass index of 25 or less (BMI is a proportion of height and weight), and men with an overweight BMI of 28 or more.
It's no surprise that the athletes were in better shape than the control group: The rugby players were metabolically healthier than the high-BMI portion of the control group, and they also had lower inflammation than both groups, despite having more of an enzyme that indicates muscle damage (due to their training schedule).
But the research team also found that the rugby players had much more diverse microbiota than both control groups, and they especially had a lot more of the bacteria species Akkermansiaceae, which is associated with lower rates of obesity and metabolic diseases.
Researchers found 22 phyla, 68 families and 113 genera of bacteria in athlete samples. In the low-BMI control group, only 11 phyla, 33 families and 65 genera were detected. The high-BMI control group had the least amount of diversity: 9 phyla, 33 families and 61 genera.
Besides their intense exercise regiment, the athletes also had very different diets than the control group. Athletes simply ate a lot more food than the control groups, and they also ate more of healthful fiber and "good fats" (mono- and polyunsaturated fat) than the high BMI group.
Protein intake especially divided athletes from the control groups; it made up 22 percent of the calories athletes ate, and 15 percent of that protein came from supplements. Meanwhile, protein made up 16 percent of calorie consumption for the low BMI group, and 15 percent for the high BMI group. Supplements were not a significant source of protein for either control group.
Analysis of the microbiota revealed correlations between bacteria and exercise levels, as well as bacteria and protein consumption. But the separate effects of exercise and protein consumption still need to be worked out, said Shanahan in an email to HuffPost.
"We don’t know for certain if it is the exercise per se or the dietary changes accompanying exercise which mediate the change in diversity of the microbiota," wrote Shanahan. To answer that question, he's currently working on a gut bacteria study that divides non-athletes into three groups: people with an exercise regime, people who will both exercise and eat a high-protein diet, and finally people who will eat just the high-protein diet.
Despite the unknowns, Shanahan is comfortable asserting that exercise can benefit gut bacteria -- and you don't have to exercise like a professional athlete to get similar results.
"Regardless, what one can say for now is that exercise and diet can have a beneficial effect on microbial diversity, metabolic profile and inflammation," wrote Shanahan. "We would not recommend the extreme levels of exercise that were undertaken by the professional athletes in the present study. It is probable that any level of exercise is preferable to none and will help."
This study adds to an emerging research interest in the trillions of bacteria in our guts -- and how those can impact our overall health. Previous research has found that a healthy microbiome -- that is, ecosystem of "good" gut bacteria -- could offer new ways to address life-threatening food allergies; prevent alcoholics from developing pancreatitis; and could potentially contribute to type 1 diabetes management.