All language subtitles for The Gut Our Second Brain.en

[MUSIC PLAYING]

This is not a stomach.

It's a hub of intelligence.

It houses the equivalent
of a small pet's brain.

[NON-ENGLISH SPEECH]

We have 200 million neurons
in our gut about as many

as Timmy has in his cortex.

And we can say that Timmy
is really very intelligent.

A cat and a dog each
have about the same number

of nerve cells as the gut.

If they're intelligent, the
gut is every bit as smart.

Scientists have some
surprises in store for us,

having rediscovered
what common sense has

known for a long time.

People of a nervous
disposition get

butterflies in their stomach.

Cowards lack guts.

And we sometimes
act on gut instinct

with the gut feeling of fear
in the pit of our stomach.

At times, we get the distinct
feeling our brains are not

the only captain on board.

But what exactly do scientists
know about the interplay

between the gut and the brain?

The gut is home not just
to millions of neurons,

but also to hundreds
of billions of bacteria

that secretly influence
our most daring exploits

and our personalities.

A voyage into the secret
territory of our bowels

in search of our second brain.

[MUSIC PLAYING]

This story starts at
Columbia University

in New York City when
Michael Gershon dared

to proclaim that our gut houses
a sensitive and intelligent

organ.

It's important
to focus in the gut

to explain to the world
this is one important dog.

And it's not just a
repulsive serpentine

snake-like disgusting thing, but
a vibrant lifeline to success.

So there was a dark age of
knowledge of the second brain.

And then it was rediscovered.

And I helped to rediscover it.

And since it was a
Renaissance, that

makes me the Leonardo
of the bowel.

If Leonardo da Vinci
had had the chance

to use the microscope
Michael Gershon uses,

these are some of the neurons
he would have observed.

200 million of these neurons
line our intestine wall.

They span the length
of our digestive tubes,

helping us to digest food.

Digestion is
surprisingly complicated.

You have to do things that
are very hard to do in

a laboratory-- break food
down that you eat and make it

into tiny little molecules
that you can absorb and use

to run your body.

And for that, you need
a lot of nervous power.

[MUSIC PLAYING]

Our two brains resemble
each other like brothers.

The upper brain houses the
central nervous system.

And the lower brain houses
the enteric nervous system.

They even share similar
scientific names.

But did evolution
really need to equip us

with two separate brains?

The reason that evolution
would want to have this brain

outside is very
similar to the reason

we all keep personal
computers on our desks.

By peripheralizing it,
sending it off to the gut,

it's more efficient,
more effective.

The brain doesn't have to
connect with huge cables

to the gut.

It can leave it there.

And you don't have to expand the
brain to hold several million

more nerve cells.

[MUSIC PLAYING]

Scientist, Michel
Neunlist, who

is based in Nantes
in Western France,

is one of the world's
leading experts

on the enteric nervous system.

For Michel in the history
of our two brains,

the first brain is not
the one we think it is.

[NON-ENGLISH SPEECH]

The second brain has had
its name usurped really,

because I consider it to be the
first brain, the original brain

even.

Primitive,
multicellular organisms

were initially composed
of just a digestive tube.

The enteric nervous
system developed

within this digestive tube.

[MUSIC PLAYING]

If we travel back in
time, it becomes apparent

that our upper brain evolved in
order to better feed ourselves.

The appearance of
the brain coincided

with that of our eyes and
ears useful for seeking food.

Without dividing the
tasks up like this,

we would still be
spending all our energy

digesting, digesting,
and digesting some more.

[MUSIC PLAYING]

The turning point in this
spectacular evolution

of our brain is linked to
a technological invention,

the domestication of fire.

1.5 million years
ago, Homo sapiens

was still called Homo ergaster.

And he had just
invented the barbecue.

[NON-ENGLISH SPEECH]

Cooking is a form
of pre-digestion.

So thanks to cooking first,
chewing became easier.

And we, therefore, invested
less energy and physical effort.

Secondly, when cooked food
arrives in the stomach,

digestion is easy.

And we can recuperate
16 times more energy

with a lot less investment.

As the first brain worked
well, the second brain

took advantage of that
and was able to develop.

In theory, it could not have
happened at all, but it did.

[MUSIC PLAYING]

[NON-ENGLISH SPEECH]

Cooking our food
meant that we could

jump some physiological hurdles,
in other words, the constraints

linked to the available
energy a large brain needed.

And from there, from
Homo ergaster onwards,

the first brains, which measured
700 to 800 cubic centimeters,

gradually evolved over
hundreds of thousands of years

into very large brains,
like for example,

those of Neanderthal
man or Cro-Magnon.

Cro-Magnon, that's you and me.

This brain increased to 1,500
to 1,600 cubic centimeters

without any change in body size.

[MUSIC PLAYING]

So our brain evolved.

And now, we can think
of something other

than our stomachs.

Thinking on one
side and digesting

on the other-- a neat
division of tasks in theory.

But as always, the reality
is more complex-- firstly,

because our two
nervous systems, which

are connected by
the vagus nerve,

are in constant
conversation, secondly,

because the brain
and the stomach

use the same neurotransmitters.

Neurotransmission
is the language

that nerve cells speak in
order to talk to one another.

And neurotransmitters
are the words

that each nerve cell puts
out that another nerve

cell can understand.

Now, serotonin is
one of the words.

Serotonin, Michael Gershon
has dedicated his life

to understanding the
meaning of the word, which

changes according to
the context it's in.

And this is what
he has discovered.

In the upper brain,
serotonin means well-being.

In the gut, it sets the
pace for intestinal transit

and regulates our immune system.

It is depicted here
in red, with the cells

of our intestine wall in blue.

But surprising as it may seem,
95% of our body's serotonin

is produced in our gut.

This serotonin acts
on the digestive tube.

But also more
surprisingly, it is

released into the bloodstream
and acts on the brain,

in particular in the
hypothalamus, which

is a zone that
manages our emotions

and takes part in the
regulation of emotions.

When the gut and
brain converse,

the messages they exchange
transit via the vagus nerve.

But we've known that
for a long time now.

What researchers
have just discovered

is that the serotonin that
transits clandestinely

via the blood stream
towards the brain

interferes with our emotions
in a much more complex way.

Destined for the gut, this
surplus of information,

which in theory has no real
business being in the brain,

can sometimes lead
to misunderstandings.

[NON-ENGLISH SPEECH]

We already knew that
our emotions could indeed

influence our gut.

Now, what we're seeing
is that our gut can also

influence our emotions.

Under normal conditions, the
exchanges between gut and brain

take place without us
even knowing about it,

making it difficult
to study them.

But as always in science, by
observing what goes wrong,

we can gain a
better understanding

of how things work.

Irritable bowel
syndrome, or IBS,

is unfortunately an
obvious case study

for examining the communication
problems that sometimes crop up

in the brain-gut couple.

It's a very common disease,
affecting 1 in 10 people

and is characterized by
severe abdominal pain.

[NON-ENGLISH SPEECH]

The syndrome is characterized
by digestive difficulties,

abdominal pain, and a
disruption of transit time,

but without us
being able to find

any so-called
organic malfunctions

from the various
exams we carry out,

whether via colonoscopy,
gastroscopy, scan.

That's why these people can't
understand what's going on,

because we usually
tell them, well, we've

run extensive tests,
and we found nothing.

And they often say, but
doctor, I'm in pain,

there's something wrong with me.

So it's important to explain
to them that currently we

explain these function disorders
by malfunctions occurring

between our brain and
our digestive tube.

[MUSIC PLAYING]

What is causing these
communication problems?

What is sending out the wrong
messages-- our upper brain

or our lower one?

These questions are mobilizing
researchers all over the world.

In Munich, Michael
Schemann considers

that IBS could originate
in the intestine wall.

Along with his team,
he's trying to pierce

the mysteries of this
neuron-packed area

of intestinal skin that lies
at the crossroads of often

delicious, but sometimes
painful sensations.

[NON-ENGLISH SPEECH]

It's hard to believe,
but inside this sausage

is an enteric nervous system.

It's a typical Bavarian
recipe-- white sausage,

and its skin is nothing other
than a natural intestine, which

contains the enteric
nervous system.

More than just
dissecting sausages,

the researchers are
cutting into intestines.

Their work involves
measuring the activity

of human intestinal neurons.

[NON-ENGLISH SPEECH]

We're basing our work on
the following hypothesis--

one of the causes of IBS is
due to a faulty communication

between the mucosal
surface and the gut nerves.

To test this hypothesis,
Michael Schemann

compares the neuronal activity
of the submucosal nerves

of healthy patients with
those of ill patients.

And this is the result
on an ill intestine.

This film is the very
first visual presentation

of the signals that are emitted
and received by the nerve

cells of our intestine.

It shows that the
neurons of ill patients

are far more active than those
of the healthy population.

[NON-ENGLISH SPEECH]

We conclude that these
patients are indeed

suffering from a
hypersensitive nervous system,

a sort of intestinal
neurosis if you like.

[MUSIC PLAYING]

Michael Schemann hopes
his discovery will soon

result in a drug
that will normalize

this neuronal hyperactivity.

In the meantime, at
the University Hospital

of Grenoble, Bruno
Bonaz has observed

that the disease is often
brought on by stress

or traumatic events.

He uses a more global
method to provide relief

for his patients.

Do sit down.

Take slow, calm, deep breaths.

You're feeling serene.

You're smiling.

You're feeling very
relaxed, nice and relaxed.

[NON-ENGLISH SPEECH]

Why does the stomach
bear the brunt of all that?

I think there are lots of
things we carry subconsciously

in our stomachs, which is
where the idea of working

on that area with
hypnosis comes from.

Hypnosis can, in
particular, encourage

phenomena of adjusting to pain.

It means, these patients
perceive less pain.

And their state of
hypervigilance is reduced.

So they will perceive less pain.

And now, you can feel a
pleasant feeling of warmth

in the area of your stomach
around your abdomen.

Concentrate for a while on
the gentle, pleasant warmth

you feel in your stomach.

If you imagine that the
gut is sending signals

to the brain that are
disturbing and the brain finds

these signals
intolerable, hypnosis

can be used to
essentially anesthetize

the brain to these signals.

So it's getting the same
signals that are bad,

but because of hypnosis, they've
suddenly become tolerable.

Although scientists don't
understand the exact mechanisms

as yet, neuroimaging
has enabled them

to localize the
effects of hypnosis

on the brains of patients
subjected to intestinal pain.

[NON-ENGLISH SPEECH]

Here, you have four cross
sections of the brain.

When you experience
abdominal pain,

you activate the zones
that are represented here,

like the brain stem here, the
thalamus, the insular cortex

here, the anterior cingulate
cortex, and the frontal cortex.

And we now know
that hypnosis can

modulate the activation
of these zones that

are involved in pain.

So it's clear that hypnosis
is not just all in the mind,

but is something that
has a neural, anatomical,

and functional substratum.

[MUSIC PLAYING]

Scientists are
only just beginning

to understand the secret
silent conversation that takes

place between gut and brain.

Our minds are constantly
influenced by our body's

internal chemistry.

Even our dreams, the most
mysterious expression

of our inner lives,
are particularly

sensitive to the
serotonin emission

that happens during our sleep.

Could the unconscious,
the notion

discovered back in ancient
times and reinvented by Sigmund

Freud, be located in our gut?

The enteric nervous
system can affect

how you feel by sending signals
to the brain that do not

reach consciousness
and can change the way

the brain perceives the world.

Your ability to think happily,
your ability to think well,

your ability to resist
depression and anxiety

can be very influenced
by the messages

that the gut sends to the brain.

So to that extent,
it's a contributor

to your unconscious.

[NON-ENGLISH SPEECH]

If we don't have
emotions or feelings,

we become completely irrational.

Freud's approach is
fascinating, because he said,

the ego is not master
in its own house.

Well, perhaps not in the brain.

And perhaps, the ego's
house is down there.

So perhaps, that
ego is in the gut.

Yes, I like that idea.

Gastric psychoanalysis
sounds good to me. [LAUGHTER]

[MUSIC PLAYING]

For the time being,
gastric psychoanalysis

is still on the
lookout for a founder.

But so striking is the
anatomical similarity

between our two
brains, that scientists

are starting to
wonder very seriously

if the stomach and
the head might not

share their illnesses as well.

Certain neurological illnesses,
like Parkinson's disease,

may even originate in the gut.

The University
Hospital of Nantes,

which receives 2,000
Parkinson's patients a year,

is the ideal place to
study the hypothesis.

[NON-ENGLISH SPEECH]

We're going to do a few
small movements to see

the current state
of your condition.

Can you do this with
your right hand?

Give it a little
shake like this.

So that's difficult for you.

So in your day-to-day life, that
must hamper all your actions,

like eating, for example.

It blocks.

It blocks.

He can't lift his arm.

He can't lift his arm.

So you have to help him.

Yeah, he can't feed himself.

For a long time,
Parkinson's disease

was considered to be a condition
that destroyed neurons located

in a particular area of the
brain known as the substantia

nigra, which is Latin
for black substance.

Yet, doctors have observed
that the disease is often

also accompanied by major
digestive disturbances.

Scientists have, therefore,
put forward the theory

that it affects not only
brain cells but also

our guts' neurons.

[NON-ENGLISH SPEECH]

Among certain
patients prematurely,

before the first
motor signs appear,

you can find signs of the
digestive tract being affected,

such as constipation
or an impairment

of the sense of smell.

So as this is rather
premature, some researchers

have put forward the hypothesis
that the disease could

originate peripherally
and then spread gradually

along the nervous system
and into the brain

and then, in a
subsequent stage, become

far more widespread
in the brain, which

would explain why patients
develop intellectual impairment

and trouble with balance in the
final phase of its development.

[MUSIC PLAYING]

The real origin
of the disease,

whether it's in the
gut or the brain,

has not yet been established.

But Michel Neunlist
and the neurologist

of the University
Hospital of Nantes

wanted to find
out more about it.

In 2006, they decided
to work together

to prove that
Parkinson's disease can

be diagnosed via a simple
intestinal biopsy of a living

patient.

Today, that task has
been accomplished.

In a simple routine biopsy,
there are 150 neurons.

And their condition reveals a
lot about our brain neurons.

[NON-ENGLISH SPEECH]

What was observed among
Parkinson's patients

was that, in these
biopsies, lesions typical

of Parkinson's disease
were found in the gut

neurons, the same
lesions that were found

in the central nervous system.

This is an
extraordinary result.

Whereas a biopsy of the
brain is potentially

dangerous for the patient,
an intestinal biopsy

is a harmless procedure.

[NON-ENGLISH SPEECH]

As a gastroenterologist,
I would never

have imagined taking part in
understanding or diagnosing

neurological diseases.

And yet, in the case
of Parkinson's disease,

we can visualize
and give information

on what is happening
in the brain--

from our brain that is
located in the intestine,

as though we were opening
a window onto the brain.

And that's absolutely fantastic.

[MUSIC PLAYING]

What the scientists in
Nantes have discovered

provides enormous hope.

In two or three
years' time, they

hope to be able to carry
out these routine biopsies

on people at risk.

Given that the digestive
symptoms of the disease

can occur 20 years before
the onset of motor symptoms,

an early diagnosis could
enable earlier and, therefore,

more efficient treatment
of the disease.

In the meantime, the idea
of looking at the stomach

in order to better treat the
mind is starting to gain ground

[NON-ENGLISH SPEECH]

The idea of the gut as an
open window onto the brain

has been shown to be valid
for Parkinson's disease.

The question we'll
also be exploring now

is to try and see if
this hypothesis applies

to other neurodegenerative
diseases and, in particular,

Alzheimer's disease or other
pathologies, this time more

neurodegenerative ones, but
perhaps also behavioral ones,

such as autism and
psychiatric pathologies.

[MUSIC PLAYING]

On closer
inspection, our world

resembles a gut made up of tubes
and entrails, in which fluids,

information, and
signals circulate along

increasingly complex networks.

Science is only just
starting to take into account

the complexity of
these exchanges.

And their emerging properties
remain to be discovered.

Yet, on the other
side of the world,

traditional Chinese
medicine has been

based on a vision
of the human body

as a whole for
thousands of years.

It endeavors to regulate the
invisible energy flow that

circulates through our bodies.

In Chinese medicine, organs
talk to each other and interact

via qi, an energy that
connects us to the universe.

[NON-ENGLISH SPEECH]

The different medical
systems are based

on their cultural context.

In Western medicine,
we concentrate

on what is localized, dividing
the body into different parts

to study specific functioning.

But Chinese medicine is based
on a holistic, global vision

and focuses particularly
on the relationship

between the different
parts of the body.

Each of these two visions
has its advantages.

[MUSIC PLAYING]

The gut expert of
traditional Chinese medicine

is called Bo Zhi-yun.

We are in the CTM
Hospital of Canton,

the largest hospital
in the world

with 7 million patients a year.

[CROWD CHATTER]

Every day, its
pharmacy dispenses

10 tons of drugs,
both Western and

traditional Chinese medicine.

Here, acupuncture needles
are used alongside state

of the art medical equipment.

The Chinese have been practicing
acupuncture for 3,000 years,

although the gut
was never previously

a predominant feature of
it, until Dr. Bo discovered

abdominal acupuncture entirely
by chance, a new practice

in the country of traditions.

[NON-ENGLISH SPEECH]

It was in 1972.

A lot of students were
learning acupuncture,

and I had about 20 students
trained in Western medicine.

One day, an old worker
arrived in a wheelbarrow,

complaining of severe back pain.

I applied all the classic
acupuncture methods,

but nothing worked.

The patient was in such pain,
he was sweating profusely.

And I started getting nervous
and broke out in a sweat

myself, because a lot of my
students were watching me.

With his students
gathered around him,

the professor could
not lose face.

[NON-ENGLISH SPEECH]

I used two deep
acupuncture points

located in the stomach
along the Ren meridian.

The patient immediately
stopped crying out.

And his face suddenly relaxed.

At the time, Professor
Bo was highly surprised.

The location of these points
in relation to the symptoms

was not logical.

He then embarked upon
intensive research

to understand acupuncture
in the abdomen.

And he discovered a
highly sensitive zone

around the navel.

[NON-ENGLISH SPEECH]

The umbilical
cord is the center

of the development
of the human body,

plays a very important role
in the growth of the embryo.

Even after the
cord has been cut,

the navel continues
to play a role

in coordinating the whole body.

But we don't know much
about this hidden system.

Professor Bo's method is shown
on these three illustrations.

He has trained over
5,000 disciples, who

now practice abdominal
acupuncture in Asia, Europe,

and the United States.

[NON-ENGLISH SPEECH]

On these three
images, we can see

that the organs and the viscera
have a direct relationship

to our emotions and
our mental state.

We can see clearly that
the gut is closely related

to our brain.

Thanks to this
discovery, Professor Bo

now treats numerous pathologies.

Today, a patient who
suffers from depression

is consulting him.

[NON-ENGLISH SPEECH]

Has your condition improved?

[NON-ENGLISH SPEECH]

Yes, but it came
back a while ago,

because there were
problems in my family.

In traditional
Chinese medicine,

we say that to cure the disease,
you have to find the source.

And where is the source?

In the belly.

Lie down.

Let's start the session.

Under Professor
Bo's needles, patients

suffering from Parkinson's,
Alzheimer's, and depression

sometimes experience a
regression of their symptoms

without Western science
being able to understand

how the magic works.

Should scientists
just accept the idea

that there is an energy
that is not described

in their medical anatomy books?

To try and better understand
how his treatment works,

Professor Bo has recorded
the MRIs of healthy patients

before and after a session
of abdominal acupuncture.

[NON-ENGLISH SPEECH]

Using functional MRI,
we compared the images

of the brain of a person
before and after a session

of abdominal acupuncture.

After the acupuncture,
there is an increase

in the number of
activated zones.

The results show that
abdominal acupuncture

can improve
cognitive functioning

and regulate emotions.

[MUSIC PLAYING]

In both the East and
the West, scientists

admit that they are a long way
from understanding everything

about the brain-gut axis.

But their research
so far has led

to an astonishing discovery.

100,000 billion bacteria
live in our digestive tube.

There are 1,000 times more
bacteria inside each one of us

than stars in our galaxy.

This micro cosmos
within a macro cosmos

is the most concentrated
ecosystem on the planet.

There are 100
times more bacteria

in our gut than cells
in our whole body.

[NON-ENGLISH SPEECH]

I'm a human being.

My cells come from
the egg that was

the result of the fertilization
of the ovum of my mother

by the spermatozoa of my father.

All those cells
that proliferated

have made up my body.

Until not very long ago,
I thought that was me.

But then I discovered
that was not so.

In fact, that's just
a little part of me.

There's an enormous part
of me that's made up

of microscopic bacteria.

I am, in fact, an ecosystem.

We are more bacteria
than we are human.

We have many more bacterial
cells on our bodies--

on our bodies, in our bodies--
than we have human cells.

We have more bacterial DNA
than we have human DNA.

So we are like passengers inside
a bacterial bus, if you will.

At McMaster University
in Hamilton, Canada,

Stephen Collins is seeking
to understand the functioning

of this organized ecosystem
that researchers now

call microbiota.

We each carry one to two
kilos of bacteria inside us.

They generate about 30%
of our caloric intake,

because a lot of the food
that we eat we cannot digest.

But the bacteria can
digest it for us.

And we take the energy.

We offer the bacteria
board and lodging.

And in exchange, they
convert our food into energy.

They help us determine what is
and isn't toxic for our body.

Without bacteria, survival
would be difficult.

The immune system
in your gut, which

is the biggest immune
system in the body,

is educated by what the
bacteria inform it and tell it.

So the exposure to lots
and lots of bacteria

keeps the immune system alert.

Attention!

To the world at
large, we are merely

germs-- small, significant
bacterial growth.

But today, we stand
united, knowing full well

the glorious reward that awaits
each and every one of us.

Sure, we're just germs--

As microbes play such a
crucial role for our health,

it is of critical importance
to understand the mechanisms

of microbial colonization.

Ready, sir.

Do me proud.

Dip one, two, three.

Inside the mother's
womb, the baby

lives in a sterile environment.

But starting from the first
day of his or her life,

he or she will be
colonized by hundreds

of billions of microbes.

The first bacteria to
settle inside the intestine

will select the newly
arriving bacteria

until things stabilize, making
up a personal signature,

like a sort of fingerprint.

[MUSIC PLAYING]

Events, such as taking
antibiotics by the mother

or by the child, birth
by cesarean section,

bottle feeding rather
than breastfeeding,

and an excess of hygiene
all reduce bacterial contact

and weaken the
infant's microbiota.

I think sometime in the
future, I don't know when,

that babies will be
born with and given

the best possible flora,
that it will be given,

not only to babies to
colonize them properly,

but it will be given the
various stages through life,

particularly as one gets older,
to reinforce the microbiome.

[MUSIC PLAYING]

To find the recipe of
the ideal microbiota,

it is first necessary to know
which bacteria it contains.

At the National Institute of
Agronomic Research in France,

Dusko Ehrlich
endeavors to shed light

on the mysterious population
that has lived inside us

ever since Eve bit into
the apple of knowledge.

In order to do
so, he has decided

to study the genome of
our entire microbiota.

That's right, study the
genome of an organism made up

of 100,000 billion bacteria.

This discrete project,
called program MetaHIT,

is a great deal more ambitious
than decoding the human genome.

10 years ago, I
asked myself, what

would be most fun
for a microbiologist

to do in his professional life?

And it was very clear.

Worldwide, we had huge
sequencing capacity,

because human genome
was sequenced.

And genome of monkeys and
worms and flies were sequenced.

So couldn't we use that
capacity to sequence not only

our genome, but
also our metagenome.

The mammoth task
ended in 2010,

when researchers
published the map

of a human microbial
metagenome and ended up

with a catalog of
3 million genes.

The vast project resulted
in a surprising discovery.

We discovered so many
things, I couldn't even

begin to tell you.

But one of the most
surprising discoveries

was that we humans can
be placed in three groups

by the microbial populations
that live in our gut.

We call these
groups enterotypes.

[MUSIC PLAYING]

So in addition
to blood groups,

we are divided into three
intestinal bacteria groups

that Dusko calls enterotypes.

Their difference lies
in their capacity

to convert food into energy.

All three produce vitamins,
but to varying degrees.

The enterotypes
doesn't seem to be

related to geographical
localization, race, sex, age.

And yes, one could have much
closer enterotype to a Japanese

than to his own neighbor.

[MUSIC PLAYING]

Is it our genes, our
environment, our food?

Dusko and his
colleagues have not yet

understood what determines
these three enterotypes.

But they are trying
to determine how

the thousands of
species of bacteria

interact with our body.

The scientist's long-term aim is
to gain a better understanding

of the role bacteria
play in the onset

of certain chronic diseases.

We're all familiar with
blood and urine samples.

Soon, doctors will
analyze our stools

to find out the exact
composition of our microbiota.

It's evolutionary
way of diagnostic.

Well, we see predisposition
for diabetes, type 2 diabetes,

their disposition for
cardiovascular disease,

the disposition
for liver disease

just by examining
microbiota in people.

[MUSIC PLAYING]

Studying the bacterial
flora of obese people,

scientist Patrice Cani made an
extremely promising discovery.

He observed that a certain
type of bacteria, Akkermansia

muciniphila, which
abounds in the intestines

of a healthy
population, is extremely

rare in an obese population.

He, therefore, wanted to
examine the purpose it serves.

To do so, his team fed
mice a fat rich diet

and watched how they got fatter
with and without Akkermansia.

The experiment yielded
incredible results.

By ingesting the same quantity
of energy of fat rich food,

the animals which
received the bacteria

took twice as long
to get fatter.

What we were able
to demonstrate is

that the adipose tissue
of the animals that

received a fact rich diet but
were treated with the bacteria

stocked less energy.

[MUSIC PLAYING]

Akkermansia lives in
the mucus layer that lines

and protects our
intestinal cells

and that enables it to
converse with our cells.

[MUSIC PLAYING]

Scientists have
succeeded in finding out

how these bacteria
communicate with the cells

of the intestinal wall of mice.

[NON-ENGLISH SPEECH]

In this experiment, we are
analyzing the mouse's genes.

What we were able
to demonstrate is

that the bacteria
Akkermansia was

able to activate
the mouse's genes

that induce an increase in the
mouse's capacity to burn fat

with the result that
the mouse gets half as

fat, has half the body fat
of a mouse that does not

receive the bacteria.

[MUSIC PLAYING]

This test tube may
well contain the goose

that lays the golden egg.

We will soon be eating
this living bacteria,

either in a yogurt
or by popping a pill.

But will it really
help us fight obesity?

[NON-ENGLISH SPEECH]

From a therapeutic
point of view,

the aim is to improve
the conditions

of patients suffering from
obesity and type 2 diabetes.

The aim is not-- and
besides, it would never

work-- to say to people that
we can administer this bacteria

to them and they can
eat whatever they want

and still be protected
from obesity.

I don't think that's possible.

[MUSIC PLAYING]

Today, scientists
estimate that obesity is due

10% to genetic factors,
10% to bacteria,

and 80% to our behavior.

It, therefore, greatly
depends on our own will.

But when we talk about
will, does that necessarily

mean we are the
only ones to decide?

Is our brain the master
mind of our personality,

or is it acting under influence?

It is here, in Stephen Collins'
ultra sterile laboratory,

that the answer may lie.

If you take a germ-free
mouse that has no bacteria,

the mouse behaves in
a very strange way.

It takes risks.

It is almost irresponsible.

When you put bacteria into these
mice, their behavior changes.

They take no more risks.

They are very careful.

Why is this?

So maybe, the
bacteria are saying,

look, we want to survive,
so you better behave well.

But Stephen
Collins does not stop

at this simple observation.

In this experiment, he chose
two lines of mouse-- one

rather active and daring,
the other rather calm.

Then he administered
to each line

the microbiota of the
other line of mouse.

We took mice that
were very quiet,

and we put their
microbiota into mice that

are notoriously aggressive.

And these are Swiss mice.

And the Swiss mice
became calmer.

Then we did the
other experiment.

We took mice that
were very quiet,

and then we gave
them the microbiota

from the aggressive mice.

And the calm became
more aggressive.

[MUSIC PLAYING]

That's the
experimental evidence,

that the microbiota
influence the brain.

Who we are is not determined
solely by us as humans.

We're being influenced
by our ancestors--

the bacteria that were present
on this Earth for millions

of years before us that have
acquired a genetic repertoire

that is much greater than ours.

And now, we find that
they influence who we are

and how we are.

[MUSIC PLAYING]

The results of Stephen
Collins' demonstration

have toured the world.

In Europe, other scientists are
making mice more adventurous

simply by making
them eat bacteria.

[NON-ENGLISH SPEECH]

We already knew about
a few of those features

among a certain number of
parasites-- not bacteria,

but small eukaryotes which
live inside organisms

and change the behavior
of these organisms

by serving their own interests.

The example of toxoplasmosis
is an amusing one,

because when these small
parasites are present

in mice, they remove
the mice's fear of cats.

Certain studies even suggest
that the mice are sexually

attracted to the cats,
which is strange.

Of course, that
results in them getting

eaten by the cat, which serves
the interest of the toxoplasma,

because toxoplasma
develops well in cats.

[VIDEO PLAYBACK]

[MUSIC PLAYING]

-(SINGING) Who put her in?

Little Herman Grin.

Who pulled her out?
[LAUGHING] Ding

dong dell, ding dong-- huh?

[NON-ENGLISH SPEECH]

And there are many
examples of this.

It's very common for parasites
living in the gut of their host

organism--

[END PLAYBACK]

--to alter its behavior.

It shows to what extent there
is an interaction between what

happens in a person's gut
and what that person's brain

will order them to do.

[MUSIC PLAYING]

But before concluding that
we are being manipulated

by bacteria, it is
necessary to prove

that what happens in mice
can be transposed to humans.

In order to modify
human intestinal flora,

we have two tools-- antibiotics
to kill bad bacteria

and probiotics to
develop good ones.

Probiotics are yeast
and live bacteria

that are supposedly
beneficial for health.

They can be found in
yogurts, for example.

There is still some doubt
as to their real efficacy,

given that research on
them is in part funded

by those who market them.

In Europe, food
industry groups have

been asked to remove all
allegations of health benefits

from their probiotic-enriched
milk-based products.

What's more, evaluating
the efficacy of probiotics

is no easy matter.

[NON-ENGLISH SPEECH]

Life is not simple,
even among bacteria.

One single bacterium
is factory that

makes thousands of molecules.

And generally to make
things even more difficult,

a preparation of
probiotic bacteria

contain several
of these bacteria,

increasing the
complexity even more.

So we're a long way
from the classic one

molecule, one action standard.

[NON-ENGLISH SPEECH]

We don't understand
exactly how it works.

We know how to kill the
bad ones with antibiotics

and how to try to favor the
good ones by giving probiotics.

But in fact for the
moment, we really

don't understand very much.

[MUSIC PLAYING]

At the Center for Neurobiology
of Stress in Los Angeles,

Kirsten Tillisch
was also skeptical.

How could taking probiotics have
an effect on stress response?

To find out more,
Kirsten and her team

tested the effect of probiotics
on the brains of healthy women.

What we decided to do is
look at healthy women, who

had no pain, no discomfort, no
gastrointestinal, no anxiety

or depression.

And the task that
we chose is a task

that's been used to look
at how people respond

to emotionally negative images.

[MUSIC PLAYING]

And we thought, well, let's see
if changing what's in the gut

can change the responsiveness
to these images.

For two weeks, scientists
gave a group of 60,

perfectly healthy women yogurts
with and without probiotics.

Then they looked to see if their
brains responded differently

to stress.

Are you ready
to start the task?

OK, here we go.

So what we found was that in
people who took the probiotic,

a network of brain
regions was less active.

So it implies that the
people who took probiotics

are less reactive
to those images.

We know that in
the brain something

is changing in the
way that they're

responding to their
environment and specifically

to negative and
potentially threatening

things in their environment.

So this is the
first study that has

shown that if you
give a probiotic,

it changes something
in the brain.

This is incredibly exciting to
us, that with this simple food

that I could go to
the market and buy,

potentially I could
change something

that's going on in my brain.

[MUSIC PLAYING]

But even the most
enthusiastic scientists

recommend exercising
caution in the face

of this very recent research,
especially given that, as yet,

we don't know much about
the side effects of bacteria

on our body.

But all agree that they have
an affect both on our health

and on our brains.

We now have to recognize
that a certain component

input into our brain
comes from bacteria.

Doesn't mean we are
controlled by bacteria.

But they certainly have an
influence in who we are, in

how we behave and how we react.

So I think, we now
have to consider

that we have a third brain.

We have the big brain.

We have the little Brian.

And now, we have the
intelligence of bacteria.

[MUSIC PLAYING]

[NON-ENGLISH SPEECH]

In science, we don't just
progress by making discoveries.

We also progress by changing
models or paradigms.

What we are is linked to our
history and our environments.

These environments are
external and we're now

discovering internal.

And that's wonderful.

[NON-ENGLISH SPEECH]

We tend to think, here we are.

We're all humans.

We sit staring at our
screens with a strong sense

of our own individuality,
thinking that ecosystems

are outside the forests,
the fields, the Amazon,

that that's not us.

But in reality, things
don't work like that.

We have this bacterial
flora inside of us.

And it also exists
outside of us too.

So in fact, we're bathing
in a bacterial ecosystem

that penetrates us
and is part of us.

There's no longer this
separation between ourselves

and what is not ourselves,
between the exterior,

between me and the others.

There's one
absolutely remarkable

biological continuity.

Scientists' vision of
our body has changed.

What we formerly took for the
ultimate foundation of reality,

our individuality, is very
probably the reflection

of a more complex
reality, essentially

made up of messages,
networks, and still

very mysterious connections.

We are now thousands of
genes, billions of neurons,

and hundreds of
billions of bacteria.

We are a multitude of
links and information.

Their overwhelming
complexity reaches

far beyond the confines
of our own selves.

[MUSIC PLAYING]