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