Exercise and the ‘Good’ Bugs in Our Gut
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Being physically active may encourage
beneficial germs to thrive in your gut, while inactivity could do the
reverse, according to an innovative new study. The findings suggest
that, in addition to its other health benefits, frequent exercise may
influence our weight and overall health by altering the kinds of
organisms that live inside of us.
In recent years, there has been an explosion
of interest in the role that gut microbes play in whole-body 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 health disorders than people with low
microbial diversity, and that certain germs, in particular, may
contribute to improved metabolic and immune health.
But little science had examined the interplay between physical activity and gut bugs in people. 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
endeavor,” 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 of the players agreed to participate.
At the time of the study, the men’s national team was in preseason
training and the players were exercising strenuously for several hours
every day.
For the sake of 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 of the
men in this group exercised occasionally but lightly.
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, with
body masses well above normal. The researchers wanted to compare their
gut microbes to those of men whose weight was similar, if not their
musculature.
The scientists drew blood and collected stool
samples from all of the men, rugby players and non-athletes alike. The
volunteers also completed lengthy questionnaires about their exercise
routines and diet, and spoke with a nutritionist about their typical
daily food intake.
Then the scientists analyzed the men’s 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 man’s 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, meaning that their intestinal tracts
hosted a greater variety of germs than did those of the other men,
especially the men in the group with the highest B.M.I.
The rugby players’ guts also harbored larger
numbers of a particular bacterium, uneuphoniously named Akkermansiaceae,
that has been linked in past studies with a decreased risk for obesity
and systemic inflammation.
Interestingly, the rugby players’ blood
showed low levels of markers for inflammation, even though the men were
exercising intensely. Their muscles were being pummeled but, in
physiological terms, recovering well.
The men in both of the control groups, on the
other hand, especially those with the highest B.M.I.s and who rarely
exercised, had relatively low numbers of Akkermansiaceae in their guts
and elevated markers for inflammation in their bloodstreams.
These findings “draw attention to the
possibility that exercise may have a beneficial effect on the
microbiota,” Dr. Shanahan said, in ways that improve bodily health.
However, the results are still preliminary,
he said. This study was small and, because of its methodology, the
researchers can’t determine how exercise alters gut germs or tease out
the effects of intense exercise from those of diet. The rugby players
consumed far more calories than did the other men, with a much larger
percentage of their diet consisting of protein. Such nutritional
differences can affect which microbes thrive in the gut. The athletes
also were training at a level that few of us would be able or willing to
emulate.
Dr. Shanahan and his colleagues have begun a
follow-up study examining whether and how moderate exercise changes the
gut environment in both men and women. The results should be available
later this year.
But even in advance of those findings, he
said, it seems likely that any amount of exercise should make your gut
more welcoming to the bacteria that you want residing there.
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