If you were to switch from vegetarianism to meat-eating, or vice-versa,
chances are the composition of your gut bacteria would also undergo a big
change, a new study suggests.
The research, published in the journal Nature, showed that the number
and kinds of bacteria and even the way the bacteria behaved changed within a
day of switching from a normal diet to eating either animal- or plant-based
"Not only were there changes in the abundance of different bacteria,
but there were changes in the kinds of genes that they were expressing and
their activity," said study author Lawrence David, an assistant professor
at the Institute for Genome Sciences and Policy at Duke University.
Trillions of bacteria live in each person's gut. They're thought to play a
role in digestion, immunity and possibly even body weight.
The study suggests that this bacterial community and its genes called the
microbiome are extraordinarily flexible and capable of responding swiftly to
whatever is coming its way.
"The gut microbiome is potentially quite sensitive to what we
eat," David said. "And it is sensitive on time scales shorter than
had previously been thought."
David said, however, that it's hard to tease out exactly what that might
mean for human health.
"It's nice to have some solid evidence now that these types of
significant changes in diet can impact the gut microflora in a significant way,"
said Jeffrey Cirillo, a professor of microbial and molecular pathogenesis at
the Texas A&M Health Science Centre College of Medicine in Bryan, Texas.
"That's very nice to see, and it's very rapid. It's surprising how quick
the changes can occur."
Cirillo said it was also intriguing how fast the microbiome seemed to
recover. The study found that gut bacteria were back to business as usual about
a day after people stopped eating the experimental diet.
For the study, researchers recruited six men and four women between the ages
of 21 and 33.
For the first four days of the study, they ate their usual diets. For the
next five days, they switched to eating either all plant-based or all
animal-based foods. They then went back to their normal eating habits before
switching to the other diet pattern.
The animal-based diet resulted in the biggest changes to gut bacteria. It
spurred the growth of 22 species of bacteria, while only three bacterial
species became more prominent in the plant-based diet.
The researchers don't fully understand what the shifts mean, but, they said,
some made sense.
For example, several types of bacteria that became more prevalent with the
animal-based diet are good at resisting bile acids. The liver makes bile to
help break down fat.
Another type of bacteria, which became more common in the plant-based diet,
is thought to be sensitive to fibre intake.
The researchers speculated that the bacterial shifts might explain why fatty
diets have been linked to diseases like Crohn's and ulcerative colitis. More
studies are needed, however, before they can say for sure.
Find out more information on overweight and obesity here.
For more on overweight and obesity, visit the Human Microbiome Project.