THURSDAY, Sept. 1 (HealthDay News) -- You are what you eat --
especially when it comes to the microbes that live in your gut.
New research shows that people who eat a diet that's high in
fats and animal proteins have a certain group of bacteria that
flourish in their digestive tract, while the guts of people who eat
a more plant-based, higher carbohydrate fare favor other
What that means for human health is still unknown. But there's
increasing evidence that the "microbiota" that live in the human
gut may play an important role in health, including possibly
contributing to obesity and other ailments, researchers said.
The findings are published in the Sept. 1 issue of
In the study, researchers asked 98 healthy, non-obese America
adults to report on their usual diet and the diet they ate in the
week prior to giving a stool sample. From each sample, researchers
then isolated the DNA of the bacteria present.
The analysis showed that participants could be generally grouped
into one of two categories, or "enterotypes", based on the
prevalence of certain species of bacteria in the gut. People in the
first group had high levels of the bacteria
Bacteroides. In type 2,
Prevotella was more prevalent.
"You could see the people who consumed more animal protein and fat tended to fall into an enterotype characters by Bacteroides, whereas those who tended to have a diet high in carbohydrates [more plant-based] fell into an enterotype characterized by Prevotella," said study co-senior author Dr. James Lewis, a professor of medicine and epidemiology at University of Pennsylvania Perelman School of Medicine.
In a second experiment, researchers had 10 participants, all of
whom fell into the
Bacteroides group, stay in a research lab for 10 days. Both
groups were fed an identical diet and an identical amount of
calories, with one exception: one group was put on a high fat/low
fiber diet, while the other group was put on a low fat/high fiber
The dietary change
did impact bacteria levels in the gut, the study found, but
not enough to move the
Bacteroides group into the
That suggests that long-term dietary habits, rather than any
short term changes, have a bigger impact on gut microbiota, Lewis
The next step for researchers is getting a better handle on how
the bacteria that resides in our gut may influence the development
of disease, said Justin Sonnenburg, an assistant professor of
microbiology and immunology at Stanford University School of
Medicine. He praised the researchers for being able to correlate
specific enterotypes with actual human diets.
Though no one has yet proven a cause-and-effect relationship,
researchers have linked altered microbiota with many diseases and
conditions, including obesity, inflammatory bowel disease,
irritable bowel syndrome and potentially colorectal cancer.
What's almost certain is that gut microbes play a significant --
and underestimated -- role in human health, he added.
One theory is that our immune systems may react to certain
bacteria in the gut, triggering an inflammatory response that could
contribute to several diseases, Lewis said.
"There's also a whole another line of research that's looking into to what extent the bacteria living in our intestines is related to the host's risk of becoming obese, perhaps by influencing the efficiency of absorbing nutrients," he said.
It's known that the bacteria living in the gut help humans
harvest energy from the food we eat. If the bacteria there are
really good at that, some people may be getting more calories from
a given food that others, he theorized.
Prior studies in mice have shown that if you transplant the
bacteria in the intestines from an obese animal to an ordinary
mouse, that second one will become obese.
"The major question that springs from this work is, will long-term dietary change be able to move somebody out of their dietary enterotype?" Sonnenburg said. "This study suggests that dietary change will not do it in the short term, but may require a long term change in diet and lifestyle."
U.S. National Institutes of Health has more about
how gut microbes may impact metabolic syndrome.