Plants the microbiome and mental health
[Music]
check it out
spinach you’ve probably eaten this
hundreds of times
but did you know that on and inside this
spinach plant
are over 800 different species of
bacteria
this is not about doing a better job of
washing your veggies
these are bacterial endovites and you
can’t wash them off
even if you try plants are living
organisms
and like us they have microbiomes these
are thriving ecosystems
of live bacteria and other
microorganisms
i became fascinated by this fact about
five years ago
while collaborating on a paper about the
american gut project
researchers asked survey respondents
in an average week how many different
plant species do you eat
responses range from zero to over 30
plants in an average week
now normally nutritional guidelines
measure
nutrition intake in terms of volume for
example how many
cups of fruits and vegetables do you eat
in a given day
but here researchers particularly in
context of the gut microbiome
found that variety matters just as much
if not more the people who reported
eating
over 30 different plants in an average
week
have what we might consider an optimal
gut microbiome with high diversity
unfortunately that’s not most of us
so i asked myself what would happen if i
consumed 30 different plants a day
that would be like eating the crop from
a whole farm
every day so i went to the grocery store
and i got 30 different plants
brought them home rinsed them off
chopped them up
put them in a blender with six cups of
water and then i had 30 different plants
a day for the next month then i did it
again
then i did it again these days my
nine-year-old daughter comes with me to
the grocery store
it can be kind of fun to walk the aisles
and pick out 30 different species of
plants
i end up trying all kinds of new things
like sorrel
or raw cactus i’ve decided this is as
close as i’m going to get to living the
hunter-gatherer lifestyle
i prepare a batch of this plant cocktail
once a month
and then have a serving every evening
with dinner
this has completely changed my life by
now you might think that i’m some kind
of
nutrition junkie but actually i’m a
neuroscientist and i specialize in
anxiety disorders affective disorders
like depression
and trauma and stressor related
disorders like post-traumatic stress
disorder ptsd
mental health is a hot topic these days
and for good reason
the census bureau and cdc report that
approximately a third of americans are
reporting recent symptoms of anxiety and
depression
we desperately need new ideas to solve
our mental health problems at scale
reason i’m interested in this plant
cocktail is not because it’s nutritious
although it is and not because it tastes
good
you might not you might think that it
doesn’t but because of
up to 30 000 different species of
bacteria in this plant cocktail
and what we’re learning about the
relationship between bacteria
and mental health whether you know it or
not
sorry germaphobes we breathe in and
consume
millions of bacteria every day perhaps
billions we’ve known about the
beneficial effects of bacteria for some
time now there’s even a name for this
idea
the old friends hypothesis
if you think about it the first mammals
were burrowing animals that lived during
the time of the dinosaurs
this means for at least the last 210
million years
mammals have co-evolved with soiled
bacteria
mammals were burrowing in the soil
breathing soil
consuming soil these soil bacteria
truly are our old friends
now these bacteria can communicate with
our brain
through what’s called the microbiome gut
brain axis
there’s also evidence for a microbiome
airway or lung brain axis
and both seem to be important for
maintaining our physical and mental
health
bacteria can do all kinds of great
things for us
from synthesizing vitamins to digesting
fiber
what you need to know for this talk
however
is that many bacteria including soil
bacteria
can prevent inappropriate inflammation
in our bodies for example
growing up on a farm can protect you
from developing allergic
asthma later on in life
a recent study compared amish and
hutterite children
these two populations have a common
ancestral origin
in europe however they’ve adopted
different farming
practices hutterite communities have
adopted modern farming
techniques including the use of tractors
to plow fields
amish communities on the other hand have
maintained
traditional farming practices including
the use of large animals to help plow
the fields
compared to an average american child a
hutterite
child has a reduced risk of allergic
asthma and amish children
have an even lower risk of developing
allergic asthma
and they were able to show that just
this dust
when it was exposed to mice was able to
interact with the immune system in a way
that prevented development
of allergic airway inflammation is it
also possible
that growing up on a farm can protect us
from stress-induced inflammation
which we know is a risk factor for
developing
psychiatric disorders to address this
question
we partnered with stefan rieber and his
team at university of ohm
in germany in this case we recruited
40 healthy young men in germany
half of the men grew up on farms
with farm animals for the first 15 years
of their lives
the second half grew up in cities of at
least a hundred thousand people
without pets we brought both groups into
the clinic
and asked them to give a speech in front
of a camera
and in front of a stern-looking panel
of scientists in white lab coats and i
kid you not
giving a speech in front of a panel of
scientists and white lab coats is one of
the most stressful things that we can do
to humans in the research laboratory
what we found is that those that grew up
on farms in the presence of farm animals
had a lower inflammatory response when
exposed to this purely psychosocial
stressor
this supports the idea that exposure to
a diverse
microbial environment like you find on a
farm
can not only protect against allergic
airway inflammation
but may also protect against
stress-induced inflammation
which we know is a risk factor for
development of stress-related
psychiatric disorders
so how far can we push this
can we strategically use bacteria
to prevent psychiatric disorders
20 years ago we injected mice with the
bacterium
that was isolated from the soil and the
mud around lake kyoga
in uganda we already knew that this
bacterium
mycobacterium vaccine when injected into
mice
could prevent allergic airway
inflammation
we wanted to know if we inject mice with
this bacterium
can we also see effects on the brain and
can we see effects on emotional behavior
what we found was mice that were
injected with the bacterium
had activation of serotonin neurons in
the brain
they also acted as if we had injected
an antidepressant drug when we published
this
in 2007 this seemed really novel
but now based on what what we know about
the microbiome gut brain axis
this is not so surprising this work
led to a more recent study with dr lisa
brenner and her amazing team
at the v at the va right here in denver
colorado
for this study we recruited u.s military
veterans
with the diagnosis of post-traumatic
stress disorder
and mild traumatic brain injury
half of the veterans received a placebo
half of the veterans received a live
bacterium
that we know has anti-inflammatory
properties
veterans received the bacterium once a
day for eight weeks
then we brought them into the clinic and
exposed them to the same
psychosocial stress paradigm that i
described earlier what we found is that
those veterans
who had received the bacterium responded
with a reduced
stress reactivity after exposure to the
stressor
we also found that they had a reduced
biological
signature of inflammation
although larger trials are needed this
supports the idea that we can
use bacteria with anti-inflammatory
properties
for both the prevention and the
treatment
of trauma and stressor related disorders
like ptsd
i believe that studies of the microbiome
gut brain axis have the potential to
open up a whole new world
of options for prevention and treatment
of stress-related psychiatric disorders
for example there’s a whole new field of
psychiatry
called nutritional psychiatry a study
was published in 2019
a meta-analysis of 16 separate studies
showing that whole dietary changes
could reduce anxiety and depression
symptoms
and this was true in population studies
so people that were not depressed but
also in people with clinical depression
you might find that in the future your
doctor will provide a prescription for a
special diet
to reduce your symptoms of anxiety and
depression
you might also find that they’ll provide
a prescription
for a green prescription for increased
exposure to nature
as is currently being done in other
countries
we might even find that in food deserts
we can find
30 packs variety packs of 30 different
plants that people can just take home
and incorporate into their diet
we might be able to develop a farm in a
pill
or a forest in a pill or even a shop
where we can replace some of what we’ve
lost by moving away from nature
and into the cities now research
on bacteria and mental health is ongoing
but you can take advantage of what we
know right now
there’s a big difference between the
microbiome of someone
who reports eating five or fewer plants
in an average week
compared to someone who eats 10 plants
or 20 plants
or 30 plants or even more plants in an
average week
you can literally eat your way to better
mental health
the next time you go to the grocery
store put more
plants in your grocery cart set up a
competition with your friends and family
to see if you can increase the number of
different plants that you eat
on an average week get yourself and your
family outdoors
and expose to nature as much as possible
grow a garden bring more plants into
your home
get a dog pets are a great way to bring
more
bacteria into your home and i mean that
in the best possible way
we’ve long known about the restorative
effects of exposure to nature on our
mental health
perhaps it was always more than sunshine
and fresh air at play
it makes us wonder if the future of
mental health
was right under our feet all along
thank you
you