Original subtitles

(dramatic piano music)

- [Narrator] It's impossible to escape.

Sweet and fatty foods surround us.

They're everywhere.

And for decades,

the body has not been handling these new eating habits well.

But what about the brain?

Do our mental health, our moods,

and our brain abilities suffer

when we eat badly?

- We know that junk food is making us fat

but science is telling us now

that it might also be shrinking our brains.

- [Narrator] Mind your manners

because scientists are at the dining table.

- Diets that are high in fat and sugar

in the long term lead to changes in part of the brain

involved in memory.

- [Narrator] This is a recent field of research,

a developing science

that spotlights a new facet of nutrition.

- Habitual intake of foods high in fat and sugar

result in a reprogramming of the brain.

- [Narrator] Your brain is affected

by what you put on your plate.

(gentle music)

Everything starts with the first meals,

even before birth.

The brain is built during pregnancy.

Later on, it's functioning depends

on how it has been nourished

by the expectant mother's diet over nine months.

The consequences of poor nutrition during gestation

have been known for a long time.

But in Australia,

scientists today are concerned with the effects of nutrition

on brain function.

Felice Jacka, a professor at the University of Melbourne,

is one of the best experts

on the link between nutrition and the brain.

She examined the behavior of babies

after tracking the eating habits of 23,000 pregnant women.

- We measured their intake of junk and processed foods.

We measured their intake of the healthful foods,

foods with lots of fiber and nutrients, et cetera.

And then we looked at the emotional health

of their children

over the first few years of life,

from 18 months to five years.

Of course, taking into account things such as education,

income, the mother's mental health, parenting practices,

these sorts of things.

And what we saw very clearly

was that mothers who ate more junk and processed foods,

so sweet drinks and salty snacks

and cakes, biscuits, during their pregnancy,

their children had more of these behaviors

such as aggression and anger and tantrums.

- [Narrator] This disquieting correlation

suggests that the mother

impacts the mental development of the baby,

though the link remains to be demonstrated

on the biological level.

In any case, Felice Jacka is convinced.

- So what we also saw in this large Norwegian study

is that the children's diets seemed to be important as well.

Independent of what mom ate,

if children were eating too much junk and processed foods

and/or not enough of the healthful foods,

they had more of these anger and aggressive type behaviors

but also sadness, anxiety, worry, nightmares.

- [Narrator] Since then, Professor Jacka's conclusions

have been confirmed

by studies in Spain, the Netherlands and Canada.

There is a link between dietary quality

and mood problems in children.

But what is the nature of this link?

How does food interfere with the functioning of neurons?

Excess fat and sugar

are now in the sights of scientists working on the brain,

both excesses and deficiencies.

Junk food often lacks nutrients,

so it leaves the body and neurons in particular

in a deficient state.

In this laboratory at the University of Bordeaux,

scientists are studying

the consequences of dietary deficiencies

on the brain of mice.

(mysterious music)

This experiment is used to measure anxiety.

The animal has a choice,

explore the lighted area

or hide in the shade.

A normal mouse takes the time to examine the lighted area.

But this mouse was deprived of omega-3 during its growth.

Omega-3 is a good fat well known for its benefits

to the heart and arteries.

Instead of exploring the environment,

the mouse takes refuge in a dark corner.

It's stressed, anxious.

This experiment has been reproduced many times

on dozens of mice.

For researchers, this strange behavior

can be simply explained.

Without omega-3's to build the brain,

it does not function normally.

That's because the gray matter is 90% fat,

so it cannot produce itself.

The brain is the organ after adipose tissue

that's the richest in polyunsaturated fatty acid or omega-3.

So omega-3 is indispensable

because the body cannot make it.

We have to ingest it.

It has to come from the diet.

Oily fish, organ meat, vegetable oils and seeds and nuts

like almonds have long been main sources

of omega-3 for humans.

But these foods have become scarce

in the cuisine of industrialized countries.

Sophie Laye wanted to go further

and understand what is wrong in the brain

of these anxious mice

that were deprived of omega-3.

She examined their neurons very closely

and under the microscope anomalies clearly appear.

- [Translator] Here the neurons

bloom with all these extensions.

But there's a reduction of the extensions

when there's a dietary deficiency of omega-3.

At a more precise level,

we see the connection between the neurons

which is represented by these small protuberances.

But these synapses are also diminished.

This shows that there's an impact on the connectivity

between the neurons in the brain

and these omega-3 deficient mice.

- [Narrator] Without omega-3 available

in the development stage,

neurons have trouble communicating with each other

because the structure of the cells is changed.

- [Translator] The omega-3 that we consume

will enter the brain

and embed into the membranes of neurons.

This will give flexibility to the membranes of the neurons

and allow a better connection between them.

- [Narrator] The amount of omega-3 that enters the brain

is crucial for making brain cells more efficient

because when these fatty acids

are incorporated into the membranes,

they improve the electrical properties.

In omega-rich neurons,

the signal propagates faster.

The network is more efficient.

To deprive the brain of omega-3

is to take the risk that it will not function as well.

- [Translator] The general population

is deficient in omega-3.

We have insufficient intake of omega-3.

So it's important to pay attention to it,

especially in the prenatal, developmental period.

During this period, omega-3 embeds itself

in massive quantities into the brain.

Also in adolescents, when there's often a change of food,

and during aging

where the incorporation into the brain of omega-3

tends to be less effective.

So we must increase its intake.

- [Narrator] The first rule

for a brain to run at full speed, avoid deficiencies.

But it is still necessary

that the good nutrients are accessible

and that a varied diet is available.

What happens to neurons

when meals are poor

and above all, always the same?

The great hamster,

who has thrived for a long time

here in the planes of the Alsace region,

reveals his painful situation today.

- [Translator] Since the 1960's,

there's been a decline in the hamster population,

which is on the verge of extinction today.

And at the same time,

we've noticed an increase in the agriculture area

where corn is cultivated.

- [Narrator] Caroline Habold

wondered whether the collapse of the population

was linked to the sudden glut of corn.

So she did a laboratory experiment

by feeding the hamster this cereal exclusively.

- [Translator] During breeding,

we observed behavioral disturbances in females

which resulted in hyperaggression and hypersensitivity

as soon as there was noise in the room.

(comical music)

Above all, what we did not expect

is that these females would devour their young

the first day after birth.

This behavior was observed

in more than 80% of females.

- [Narrator] A poor diet

is enough to throw a hamster

into a murderous rage.

This calls into question a simple vitamin.

- [Translator] A vitamin B3 deficiency

is at the origin of the abnormal behavior.

When we supplemented them with vitamin B3

in addition to their corn-based diet,

they expressed quite normal behaviors

and they began to nurse their young,

to raise them in the same way

as the females that were fed a diversified diet.

- [Narrator] The deadly misadventure

of the hamster is disturbing.

Could a deficient, unbalanced diet

also trigger aggression and violent reactions?

(bombs exploding)

Archives from the last war in Holland

provide scientists with an opportunity

to study this question.

At the time, food deprivation

had a serious impact on the behavior

of an entire generation.

- [Translator] During the second world war,

there was a famine in the Netherlands.

Women who were pregnant suffered from hunger.

The children of these women

showed greater sociability problems

around 18 to 19 years later.

They had more of these issues

than other people at the same age born in another era.

- [Narrator] Impulsiveness, aggressive actions,

and recurrent violations of the law,

this generation has been particularly scarred.

Since then, many studies have linked violence

to the quality of daily food.

Ap Zaalberg is a doctor of psychology

and a political advisor

at the Ministry of Justice.

His specialty, nutrition and crime.

He is convinced that enriching the food with vitamins,

fatty acids and minerals

can reduce aggression.

(speaking in foreign language)

- [Narrator] It is difficult to test this hypothesis

in real life

because many factors and circumstances

can influence our behavior and our impulses.

In order to study food in almost ideal context

without the influence of many parameters,

he chose to go to prison.

Ap Zaalberg then launched an experiment

for which 221 detainees volunteered.

- [Translator] Here, in the Netherlands,

we conducted a study of young prisoners

in eight different prisons.

For three months, we gave them vitamins, minerals

and fatty acid supplements

and then we looked at the effect on their behavior.

We measured it in two different ways.

First, we asked the detainees how aggressive they were

and we asked the supervisors for their views on the issue.

Above all, we looked at the incident log,

the number of times detainees were punished

and we saw that solitary confinement

had fallen dramatically.

- [Narrator] In the group of inmates

whose meals were improved,

the number of incidents was reduced by one-third.

Similar studies conducted in British and Australian prisons

come to the same conclusion,

minerals, omega-3's and vitamins

added as dietary supplements

reduce violent behavior.

- [Translator] The next step

is to test whether our scientific discoveries

can be put into practice.

We have several projects

with the prison system administration.

We will see if a change in diet

can be considered a way to regulate aggression.

- [Narrator] What we eat has the power to change our moods,

to stimulate certain impulses.

But could the food on our plate

also influence our decisions,

the ones we believe we make

with the most freedom in the world?

- [Translator] When people are asked

if they think that the food that they eat

has an impact on health, most answer yes.

But when asked if diet

can also influence thoughts and decisions,

very few people are willing to believe this is the case.

- [Narrator] However, in the very serious

Institute of Psychology

at the University of Lubeck in Germany,

Professor So Young Park has, for the first time, proven it.

His work reveals

the mechanism by which food could influence our thoughts.

And for that, the researcher has developed

a rather original experiment.

Imagine that you have to solve the following dilemma.

The money on the table

is to be divided into two sums

but it's your playing partner, a stranger,

who will decide on the distribution.

- I give you two Euros and I keep eight for me.

- [Narrator] If you accept this unfair offer,

you leave with a little money

but much less than him.

If you refuse, nobody wins anything.

So what would you do?

Do you accept the offer and take two Euros

even if you feel cheated

or do you refuse and leave with empty pockets

but keep your head held high?

Well, it turns out that taking or not taking the money

depends on a surprising condition,

what you just swallowed.

(mysterious jazz music)

- [Translator] We have prepared breakfast.

The only thing that is required

is to eat everything.

I will return later for the behavioral part.

Enjoy your meal.

- [Translator] As part of this study,

we followed 24 people

who came into the laboratory twice

to have two different breakfasts.

We found that the same person

made completely different decisions

based on what they ate in the morning.

- [Narrator] To this subject,

these two breakfasts look the same.

In reality, one is far more protein-rich than the other.

The ratio of protein to sugar

is the only parameter that is changed.

A few hours after the meal,

our subject then takes several tests on a computer.

Today, he tends to accept the offer.

His interest outweighs his annoyance.

He will leave with a little money in his pocket.

Last week, he had mostly refused

and had mostly gained nothing.

- [Translator] The subject,

having consumed a high protein breakfast in the morning,

was tolerant of unfair offers.

Conversely, the subject

who consumed a high carbohydrate breakfast

was less tolerant in the face of unfair offers.

- [Narrator] On average, the subject,

when we has had little protein,

rejects unfair offers twice as often.

But how to explain this surprising result?

To understand and provide biological evidence

for this observation,

scientists performed blood tests.

- [Translator] We will send the blood

to the laboratory for analysis.

We will measure the level of hormones

and amino acids in the blood.

For hormones, we are interested in insulin, cortisol,

adrenaline and adrenocorticotropic hormone.

And for amino acids, tryptophan and tyrosine.

(speaking in foreign language)

- [Narrator] On this list,

the most important is tyrosine.

It is an amino acid

that is part of the composition of a protein

that is key for brain function dopamine.

This molecule insures communication between neurons

involved in motivation and risk-taking.

The results of the analysis

show that subjects

who have a higher level of tyrosine in the blood,

are those who more easily accept the unfair offer.

- [Translator] We therefore assume

that increasing tyrosine in the blood

increases the amount of dopamine in the brain,

which in turn changes the behavior.

- [Narrator] In other words, after a few hours,

what we eat subtly alters the chemistry of the brain

and thus, the communication between neurons,

enough to guide some of our decisions.

At the Institute of Psychology in Lubeck,

experiments are continuing to confirm this result

because it is a first

and the implications are numerous.

- [Translator] Since we eat three times a day every day,

we realize that food has immense power,

that of modifying and shaping mankind.

So it's essential to think about how we can use food

to promote our wellbeing and optimize our mental state.

- [Narrator] Between dietary deficiencies

that soften the brain,

that disrupt moods,

and the diet that interferes with everyday decisions,

it's becoming increasingly clear

that food plays a preponderant role in our psychic life.

(sexy music)

But what about junk food

dripping with sugar and bad fat?

What would happen if we ate more of it?

This is the focus of research here in Australia

at the University of Sydney.

(mysterious music)

Margaret Morris runs the only laboratory in the world

where rats are fed junk food,

the stuff you find in supermarkets

and are served in cheap fast food restaurants.

- Our experiments use a range of Western foods,

the type eaten by all of us.

So we feed our rats meat pies, chips, cakes and biscuits,

the sorts of foods that are readily available and cheap.

So we are modeling the Western world.

- [Narrator] First consequence,

the rat doubles his food rations.

The animal is never satiated.

But this is not the most surprising outcome.

- One of our chief interests

is the impact of this diet on the animal's memory.

And we can measure this easily in the rat

using a task known as the novel object

and novel place task.

- [Narrator] For this test,

the researcher places objects

in the environment of a rat.

This one comes immediately to examine them

because rodents are very curious by nature.

Once the animal has completed its exploration

and memorized its environment,

it is temporarily set aside.

- We then place the animal in the arena

with one object that's been shifted.

(mysterious music)

- [Narrator] When he returns,

the rat spends more time examining the object

that has changed places

because the rat already knows the other objects.

They are engraved in his memory.

The rat's supercharged on bad foods behave differently.

- What we observed

is the animals eating a high fat diet

or a high sugar diet

or the combined high fat, high sugar foods,

were less able to recognize, to remember,

that that object had moved.

They explored the two objects about the same.

That shows an impairment of their spatial memory.

- [Narrator] Not only do supercharged rats

have damaged spatial memory

but also other malfunctions

that are warning signals for scientists.

This tampers with the hippocampus,

a small region nestled in the heart of the brain,

essential for learning

and the consolidation of memories.

The latest studies show that in humans,

a diet that is too rich

also interferes with the hippocampus.

- We see, for example, that the quality of people's diets

is related to the size of their hippocampus,

to the size of their gray and white matter volume,

and there's starting to be intervention studies.

So for example, we see that only four days

on junk food type diet

will have an impact on cognitive functions

that are related to the hippocampus.

- You order a coke?

- It tastes good.

- You didn't care if it was a Coke, you just--

- No, I wanted a Coke.

I like the taste.

- Ooh!

- Can I get some fries with that?

- [Narrator] Is our memory,

and even our intellectual abilities

really threatened by this new way of eating?

It is still too early to be definitive about that.

But clues are piling up and worry scientists.

Margaret Morris now seeks to understand

how sugary and fatty foods

disrupt the brains of rats

to the point of affecting their effectiveness.

A hypothesis is in progress.

Eating too much fat and too much sugar

triggers an inflammatory reaction

that spreads to the neurons.

- So in response to these foods,

there's a general inflammatory response

all around the body.

This has been well described in obesity.

But it now appears to be quite an acute response as well.

And what we find is that inflammatory molecules,

such as cytokines,

are increased in response to the diet.

(mysterious music)

- [Narrator] An overly rich diet confuses the immune system.

It panics and triggers an inflammatory reaction,

especially in fatty tissues.

Our fat masses release molecules

that then propagate this inflammation throughout the body.

Neurons spared by the phenomenon

were thought to be safe behind the blood brain barrier,

the membrane that surrounds the blood vessels

and normally protects the brain.

- So there's increased inflammation in the whole of the body

and we think that this may spread to the brain.

That's because the blood brain barrier

which normally protects the brain

from inflammatory molecules

may be impaired, in fact, by the diet

and become leaky,

allowing traffic of molecules into the brain.

Importantly, we've seen changes in inflammatory molecules

within the brain of our animals in response to the diet

and these correlate with the memory loss.

- [Narrator] The inflammation that infiltrates the meninges,

then trigger a particularly surprising phenomenon.

In her laboratory, Sophie Laye

has shown in supercharged mice

that certain immune cells of the brain,

the microglial cells

begin to devour the neurons.

- [Translator] These microglial cells

within the brain are important

because they can eat dead neurons.

But when they're deregulated,

especially in a situation of unbalanced nutrition,

they start to eat neurons that are alive.

Therefore, by consuming these neurons in excessive numbers,

eventually, they will destroy

or participate in the destruction of neural networks.

That includes neurons that are alive

and that should be functional.

- [Narrator] The reaction of the microglial cells

was filmed in vitro.

These are the ones we see moving in these images.

In red, appears the fragments of neurons that they ingest.

In an obese mouse,

the activity becomes frenetic.

This phenomenon at the heart of neurons

is now suspected to significantly affect the functioning

of the brain.

- We've been saying to people for 30 years

don't eat these foods,

you might have a heart attack,

you might get cancer and diabetes.

It hasn't worked to change people's behavior.

We hope that if people understand

that what they put in their mouth

is actually really essential

to the health of their brain

and that of their children,

that might have a more profound impact

on people's dietary choices.

- [Narrator] Awareness that certain eating habits

are harmful to the brain is one thing.

But how to resist temptations.

Desires are often stronger than willpower.

Junk food, especially sugar, which is glucose,

constantly tempt us to make bad choices.

The masterful manipulator, sugar,

leads our neurons by the nose.

(goofy music)

Microscope, mini manipulator and ultrasensitive recorder,

Xavier Fioramonti is at the helm

of a machine capable of recording

the electrical activity of a single neuron.

The principle is simple,

a slice of mouse brain is washed in a liquid

that keeps it alive.

Meticulously, the researcher approaches it

with an electrode.

The operation is particularly delicate.

- [Translator] Here, I go down the pipette

in the slice of brain.

And now we will approach this recording pipette

near the neuron to make contact.

That's it, we made contact.

And now we will be able to measure

the electrical activity of the neuron.

(machine beeping)

The upward peaks that we see

are potential areas for action.

This is how neurons encode information.

- [Narrator] The time that elapses

between each peak forms the message sent by the neuron.

- [Translator] Now, we will increase

the glucose concentration in the both

and we will see if this cell

responds to this increase in concentration of glucose.

As it can be seen here,

this cell responds to the increase

with more electrical activity.

There is more potential for action

than what could be seen here

before the increase in glucose concentration.

- [Narrator] Here is the signal

of that single cell.

In the brain, neurons are all connected to each other.

Scientists suspect that glucose

has the ability to modify the activity

of entire brain areas,

those that control emotions and pleasure.

Is this how sugar ensures its grip on our will?

This is for the moment, only a hypothesis.

But today, sugar addiction is the subject

of intense research in laboratories.

And what appears more and more obvious

is that the power of sugar

is similar to that of a drug.

Serge Ahmed was one of the first to bring proof

with a very simple experiment.

Step one, he raised rats

by giving them cocaine and sugar.

Then after weeks of this diet,

he presented the animals with a choice.

(speaking in foreign language)

- [Translator] We have a situation

in which the animal has the choice

between a lever that is connected to a syringe

that contains drug solution,

and the drug in question is a hard drug

like cocaine and heroine,

and on the left, a lever allows him to control a syringe

that contains a sweet drink.

And there we see

the animal chooses to take the sweet drink.

- [Narrator] Rats selected the sugar water

four times more often that the drugs.

It's not a glucose overdose,

but the irrepressible desire is there.

- [Translator] So this experiment simply shows

that sugar has more addictive potential

than we had imagined

and it is perhaps even stronger

than the pull of hard drugs,

such as cocaine and heroine.

(dramatic music)

Today, we live in a food environment that's a little crazy.

We find sugar in a lot of foods,

as we would expect, in sugary drinks.

But we also find sugar in foods

that are not meant to be sweet,

such as ham or soup.

We could cite other examples

but it's adding sugar to these foods

that contributes to the fact

that we make people addicted to it

without them knowing it.

(dramatic music)

- [Narrator] So are we actually addicted to candy bars

and the sugar hidden in most supermarket products?

Does the addictive power

that draws in rats also trap humans?

(ominous music)

The influence of sweet food on the human brain

is being studied here at the Oregon Research Institute.

- [Eric] What this program of research has revealed

is that habitual consumption of energy-dense food

alters your neural circuitry

in exactly the same way of consumption of drugs of abuse.

- [Narrator] Eric Stiche recruited

about 100 students,

half of which are used

to stuffing themselves with ice cream,

while the others never eat it.

They all came to his laboratory

to sip a milkshake inside an MRI machine

and deliver the secret of their brain activity.

- Great Casey.

So what we're going to do today

is give you chocolate milkshake

and record the brain activity in your entire brain

as you receive and anticipate receiving chocolate milkshake

to look at the neural basis

of consuming energy-dense foods.

- [Female] Doing okay there?

- [Casey] Mmhmm.

- [Female] All right, I'm gonna move

to the other room again.

- [Casey] Okay.

- This is very simple.

We're going to basically

give you several tastes of chocolate milkshake

and all you have to do is stay very still

and after the milkshake's delivered into your mouth,

wait five seconds and then swallow

and we'll repeat that sequence several times.

- [Narrator] Using a simple tube,

the subject sips the milkshake without moving his head.

- What we found out

is that the people who never eat ice cream,

you could trace the reward circuitry,

everything lit up just beautifully

and it activated things very strongly

but in contrast, the people who ate ice cream every day,

showed a very diminished response,

there was hardly any activation whatsoever,

illustrating that regular intake of energy-dense foods

really reduces the pleasure you experience

when you consume those foods.

- [Narrator] The reward circuit is a brain region

that controls the feeling of pleasure.

It is particularly responsive to sugar consumption

but eating too much

ends up weakening its responsiveness.

At equal doses, the pleasure sensations are reduced.

- What's very interesting about these findings

is that people who do cocaine or other drugs of abuse

on a very regular basis

show a very similar pattern

that they have to escalate how much cocaine

they do on a regular basis

to experience the same hedonic pleasure

and that's because of this decreased response

of reward circuitry

when you do something

that's hedonically pleasurable too much.

- [Narrator] In other words,

it takes more and more to be satisfied.

As in rats, sugar acts on our brain like a drug.

But is its addictive power

as powerful in humans?

The question still divides the scientific community.

But Eric Stiche's experiment

reveals another more subtle,

and maybe even more pernicious effect,

the brain after a diet too rich in sugar,

becomes hypersensitive to images of food.

- The more and more you eat ice cream,

the less and less the reward circuitry is recruited

when you consume ice cream

but the more your reward circuitry is activated

when you see cues that say you might get ice cream.

So your reward circuitry fires up

when you see an ice cream store

as you're driving down the street

or you see a commercial for ice cream on the television.

The reward circuity activities much more

for people who eat ice cream all the time

than it does for people who don't.

And that prompts eating in the absence of hunger

that drives obesity and weight gain.

- [Narrator] The direct influence

of food on our brain

plays a crucial role in what we choose to eat each day.

Feeding behavior turns out to be

an extremely complex phenomenon.

Public health issues push scientists

to study all aspects

that govern the choices we make on a daily basis.

(crying)

(slapping)

What is really going on in the brain

when choosing a dessert rather than a starter,

fish rather than red meat?

Who is really pulling the strings?

Carlos Ribeiro's laboratory

leads research on food choices.

- What we really want

is to find all the components,

all the genes, the molecules, the neurons,

which direct feeding decisions.

And for that we have to be able

to look at very fine and small effect.

- [Narrator] The simplicity of this model, the fly,

makes it possibly to explore new avenues, new hypotheses.

To understand the feeding behavior of the fly,

Carlos Ribeiro has just developed a machine

that follows in detail

the choices made by the insect

when it goes to the table.

- When it's touching the food,

which is in the other electrode,

with its tongue, the proboscis,

then we can measure that with the sensor here

which is the same sensor

which you use on you iPad and your iPhone

to detect touch on the screen.

Just that here, we don't detect the touch on the screen

but the touch of the food.

And so we can really now dissect and analyze

the choice of the fly,

if she eats protein or sugar,

but also when she's eating from the different foods

how it eats, how much it eats,

how fast it eats, how often it eats,

and really dissect all the details of the decisions

which are controlled by the brain.

- [Narrator] Thanks to this technique,

Carlos has proven that the main reason for choosing food

is first and foremost deficiencies.

Naturally, protein-lacking flies

prefer protein-rich food.

But as Ribeiro looked more closely,

he observed that that is not always the case.

- Sometimes actually we had some flies

which didn't have this strong urge to eat protein.

And then we were wondering why that was the case, right,

and so when we looked at it,

it turned out that the flies

which had no craving for protein

had gut microbes.

And so following up on many experiments,

we could show that there are two specific gut microbes

which when they are in the fly,

they suppress protein appetite

and therefore these two microbes

have a very important influence

on protein cravings in flies.

- [Narrator] Flies, when choosing their diet,

are influenced by the bacteria in their gut.

This unexpected discovery

obviously raises an important question,

does the bacteria in our own intestinal flora,

that which scientists call microbiota,

also work on our brains?

Do they play a role in our food preferences?

At Cork University in Ireland,

John Cryan pioneers microbiota research.

He has managed to prove that in mammals

the bacteria of the gut

intervene in certain behaviors.

- When you take microbes from highly anxious mice,

and transplant them to normal anxious mice,

they become much more anxious and vice versa,

that even when you take them from normal,

you can normalize the stress response and the anxiety.

- [Narrator] Scientists are even beginning to understand

how these bacteria interact with neurons.

- Here we go.

Okay, so we take out the organs.

This uncovers the Vagus nerve.

See here in yellow,

this is the long wandering nerve

that communicates with all of the organs,

all the way down into our intestine.

And this is really one of the key pathways

for communication between our gut and our brain.

And what we've shown some years ago

with our colleagues in Canada in a mouse model

that when we cut the Vagus nerve,

all of the effects

that we've seen with a certain microbe were gone.

So this tells us that the Vagus

is one of the key pathways of communicating

from our gut all the way to our brain.

We still need to figure out

well what happens when it gets to the brain

and comes to a region in deep in the brain stem

and then from there the signals get to the key circuits

that underpin complex behavior like food intake

and that's something we're working on right now.

- [Narrator] The influence of bacteria

on our food preferences

remains to be demonstrated.

On the other hand, it is established

that these preferences act on mood and anxiety.

Scientists now even consider the microbiota

to be a kind of intermediary,

a link between food and our brain.

- The main factor that influences

the composition of these microbes

is the food we take.

Diet and the diversity of the diet

is really important

from the moment we're born until we die

in shaping the composition of the microbes.

And so we're beginning to realize the importance

that what we eat has on what's in our microbes

and how that's influencing what's going on in our brain.

- [Narrator] One way or another,

our wellbeing depends on our microbiota.

A good diet for our mood

is a diet that is suitable for bacteria

in our intestines first.

This has led to the idea

of using food to pamper one's brain

and maintain one's mental health.

And for this, it is the famous Mediterranean diet

that seduces scientists.

- The traditional Mediterranean diet

is really high in a diverse range of plant foods.

So lots of different leafy greens

and different colored vegetables

but also fruits,

very importantly legumes,

so this is your beans and lentils and chickpeas,

nuts, nuts and seeds, fish

and of course olive oil.

Olive oil is a very important component

of the Mediterranean diet.

And we think that that diversity

leads to more diversity in the gut microbiota,

the microbiota that live in our gut.

And that diversity in the gut

has been linked to good health outcomes.

We ran the first study last year

where we recruited 67 people with major depression,

they received dietary support with a clinical dietician.

Now over a three month period this trial took place,

and at the end of that

when we measured their depression again,

we saw that the degree of change in their diet

correlated with the degree of change in their depression.

So the more they moved towards a Mediterranean diet,

the more their depression improved.

- [Narrator] Placing the kitchen

at the surface of your brain

is an idea that's catching on.

Scientists are now exploring ways to do that.

Spices praised for centuries

by traditional Indian medicine

are now studied in laboratories

for their virtues related to the mind.

Red fruit and berries

also have high expectations.

The polyphenols they contain

have the ability to reinvigorate neurons on the decline.

- [Translator] These polyphenols,

especially those from red fruits,

are found to reverse the cognitive decline

in aging mice.

That is to say,

these animals are protected

with any memory problems they may have.

And this leads us to human trials.

In this case,

a very recent study was conducted

on more than 200 subjects, age 65 and over.

In the group, some were healthy

but facing normal decline due to age.

To rebound their health,

they consumed large doses of polyphenols.

- [Narrator] Are red fruits, berries and spices,

the miracle ingredients for eternally young neurons?

It is still premature to proclaim it.

Science is just beginning

to uncover the secrets of this unexpected relationship

between diet and the brain.

The ideal menu for strengthening the brain

remains largely a mystery today.

But it seems that a diversified, balanced diet,

low in processed food and sugar

and favoring fruits and vegetables,

is the best way to preserve one's mental faculties.

- My grandmother said you are what you eat so eat well.

And what we're realizing now

is that science is beginning to understand

how true she was.

- And I think in the next few years,

we'll start to really get to a point

where we can understand maybe personalized nutrition,

personalized medicine,

and a very clear understanding of how

food interacts with the brain.

- [Translator] If we limited the deficiencies,

would that reduce crime?

Too early to say.

What we do know is that when you bet on healthy eating,

it has effects on behavior.

- The more we overeat Snickers bars,

we become hypervigilant to Snicker cues

and then we eat a lot of Snickers.

And we create that monster in ourselves.

So the best thing to do if you have kids

is feed 'em healthy foods

and not get 'em used to eating this kind of crap.

I can't believe I just said crap, sorry.

(mysterious music)