DIET AFFECTS MALES ' AND FEMALES' GUT MICROBES DIFFERENTLY
The microbes living in
the guts of males and females react differently to diet, even when the diets
are identical, according to a study by scientists from The University of Texas
at Austin and six other institutions published this week in the journal Nature
Communications. These results suggest
that therapies designed to improve human health and treat diseases through
nutrition might need to be tailored for each sex.
The
researchers studied the gut microbes in two species of fish and in mice, and
also conducted an in-depth analysis of data that other researchers collected on
humans. They found that in fish and humans diet affected the microbiota of
males and females differently. In some cases, different species of microbes
would dominate, while in others, the diversity of bacteria would be higher in
one sex than the other.
These results suggest that any therapies designed to improve
human health through diet should take into account whether the patient is male
or female.
Only in recent years has science begun to completely appreciate
the importance of the human microbiome, which consists of all the bacteria that
live in and on people's bodies. There are hundreds or even thousands of species
of microbes in the human digestive system alone, each varying in abundance.
Genetics and diet can affect the variety and number of these microbes
in the human gut, which can in turn have a profound influence on human health.
Obesity, diabetes, and inflammatory bowel disease have all been linked to low
diversity of bacteria in the human gut.
One concept for treating such diseases is to manipulate the
microbes within a person's gut through diet. The idea is gaining in popularity
because dietary changes would make for a relatively cheap and simple treatment.
Much has to be learned about which species, or combination of
microbial species, is best for human health. In order to accomplish this,
research has to illuminate how these microbes react to various combinations of
diet, genetics and environment. Unfortunately, to date most such studies only
examine one factor at a time and do not take into account how these variables
interact.
"Our study asks
not just how diet influences the microbiome, but it splits the hosts into males
and females and asks, do males show the same diet effects as females?"
said Daniel Bolnick, professor in The University of Texas at Austin's College
of Natural Sciences and lead author of the study.
While Bolnick's
results identify that there is a significant difference in the gut microbiota
for males and females, the dietary data used in the analysis are organized in
complex clusters of disparate factors and do not easily translate into specific
diet tips, such as eating more vegetables or less meat.
"To guide
people's behavior, we need to know what microbes are desirable for
people," said Bolnick. "Diet and sex do interact to influence the
microbes, but we don't yet know what a desirable target for microbes is. Now we
can go in with eyes open when we work on therapies for gut microbe problems, as
many involve dietary changes. We can walk into those studies looking for something
we weren't aware of before. All along we treated diet as if it works the same
for men and women. Now we'll be approaching studies of therapies in a different
way."
Why men and women
would react differently to changes in diet is unclear, but there are a couple
of possibilities. The hormones associated with each sex could potentially
influence gut microbes, favoring one strain over another. Also, the sexes often
differ in how their immune systems function, which could affect which microbes
live and die in the microbiome.
One notable exception
in Bolnick's results was in the mice. Although there was a tiny difference
between male and female mice, for the most part the microbiota of each sex
reacted to diet in the same manner. Because most dietary studies are conducted
on mice, this result could have a huge effect on such research, and it raises
questions about how well studies of gut microbes in lab mice can be generalized
to other species, particularly humans.
"This means that
most of the research that's being done on lab mice -- we need to treat that
with kid gloves," said Bolnick.
Bolnick's co-authors
are Lisa Snowberg (UT Austin); Philipp Hirsch (University of Basel and Uppsala
University); Christian Lauber and Rob Knight (University of Colorado, Boulder);
Elin Org, Brian Parks and Aldons Lusis (University of California, Los Angeles);
J. Gregory Caporaso (Northern Arizona University and Argonne National
Laboratory); and Richard Svanbäck (Uppsala University).
This research was
funded by the Howard Hughes Medical Institute, the David and Lucile Packard
Foundation and the Swedish Research Council.
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