Food on the Brain The Secrets of Your Food

'How often do you stop and really think about your food?'

Look at all this lovely fat and sugar.

Yummy.

'Do you ever wonder why you eat what you eat,

'What cooking does to food...'

Delicious.

'..or what effect it has on your body?'

I trained as a medical doctor and I'm absolutely obsessed by nutrition

and the hidden chemistry of food,

so I've teamed up with botanist James Wong to explore food.

Each of us coming from very different perspectives...

Truly delicious.

..together we have taken over

the country's leading food science lab...

..to deconstruct some of our favourite foods...

It's all sunk to the bottom.

..and to reveal some truly remarkable secrets.

I want to find out what effect food has on us and our biology,

right down to the molecular level.

As a botanist, I am fascinated by the massive diversity

of edible plants on our planet.

I'm going to put them under the microscope to discover

exactly how their biology interacts with our own.

So join us as we seek out

the most remarkable food stories on the planet

and reveal the hidden science of our food.

We humans are peculiar.

We eat foods no other animal would eat.

On average, we spend 67 minutes a day eating.

Which, over a lifetime,

adds up to nearly three and a half years at the table...

..but we spend even more time thinking about food.

When we're hungry, food begins to dominate our thoughts

and, of course, our brains.

And what's remarkable is we're beginning to understand exactly

why certain foods create such cravings in us all.

In this episode

we'll be revealing how food really works on your brain,

why we find some foods unbelievably delicious and delightful,

but why others, well, they're quite frankly disgusting.

This is the science that explains why food has such tremendous power

over us and our behaviour.

To start, how can we get a measure of how much our brains love or hate

a particular food?

Rather than eat, I'm going to use sight and smell alone to measure

something we can't stop ourselves producing when we're around food -

saliva.

So, what I've got here is a little swab and it weighs 0.68g.

Put that in there...

and I've got what I'm told is a delicious meal underneath here

so let's have a look.

It doesn't smell delicious, I have to say.

Oh, God! That's revolting.

HE COUGHS It looks completely rancid,

I have no idea what it is.

'This is actually a delicacy in China.

'It's a preserved egg called a century egg.'

It reeks of ammonia and hydrogen sulphide, the smell of rotten eggs.

So what will the saliva test reveal?

In theory, the more I like the food, the more I should salivate.

So, let's see what effect that has had on my...

saliva.

0.88, so it's gone up a little bit.

I think that was in anticipation of something

which turned out to be utterly revolting.

I'm not producing much saliva.

I really don't want to eat this.

Right.

Dish number two, which I am also told is delicious,

although by now I'm deeply suspicious.

Smells better anyway.

OK, what is it?

And it is chocolate cake, hurrah!

Now, yeah, that smells nice and I can feel those...

saliva flowing. Let's see if that has any measurable effect.

Yeah, we are up to 1.83 this time, so lots of saliva there.

For one of my favourite foods, chocolate,

I produced about six times as much saliva.

So this shows just how much the look and smell of food alone can fire up

our brains and juice up our salivary glands.

But why do we do it?

Well, producing saliva helps us start digesting our food the moment

it reaches our mouths.

And that's because saliva contains digestive enzymes.

And it's perhaps no surprise that I drooled over chocolate because the

chemistry of chocolate makes it the world's most craved food.

We Brits eat an average of almost 7.5 kilos of chocolate every year.

The mere sight of it may be triggering feelings of desire

in your brain right now.

But just how does it create such strong cravings?

I've come to Peru to discover how we transform chocolate from raw,

bitter beans into bars of deliciousness.

I want to understand exactly why we crave it so much.

It's especially strange because in its raw state

the cocoa plant is not at all what you might expect.

Wow! Look at that.

You break open this thick husk and you've got sticky ivory pulp

that is...

It is truly delicious.

It has this incredible tropical flavour that's halfway

between lemonade and a custard apple, if you've ever had that,

sweet, acidic, sticky.

I'm sorry for being gross, but...

The bit that chocolate's made out of is the bean on the inside,

if you were to spit it out.

It's amazing that anyone thought that beneath sticky, sweet,

delicious flesh,

the rock hard super-bitter bean on the inside could make good eating.

The processing of chocolate begins

as soon as the pods are off the plant.

They're left to ferment in their own juices...

..where naturally occurring yeast breaks down sugar into alcohol

which, in turn, helps remove the bitter alkaloids from the beans.

Then the beans are dried and they're still raw and quite bitter,

nothing like the chocolate we know and love.

What happens next will soon get

my grey matter crackling with excitement.

The beans are put in a kind of oven.

What this does is it roasts the beans

and that's really key to bringing out that kind of

toasty, warm, characteristically chocolaty flavour.

120 degrees, there they go.

All this processing creates hundreds of new chemical compounds

in the chocolate beans.

And it's converting the otherwise odourless compounds into volatile

aroma-bearing ones, which begins to explain chocolate's popularity.

The roasted bean's still got these very fine thin shells on.

They're going in here and you can actually see all the shells

wafting up and, for the first time, you can suddenly smell chocolate.

It's...

Oh, it's good. It's really good.

The comforting aroma of chocolate actually comes from 25 different

smell molecules,

like 3-methyllbutannic acid

and dimethyl trisulphide.

And the weird thing is, on their own,

they're more reminiscent of body odour and cooked cabbage.

But with so many types of molecules

wafting out of the cocoa beans and assaulting our noses,

our brains just can't separate them out.

Instead, one combined glorious smell emerges, delicious chocolate.

But aroma is just part of the story.

Cocoa beans are incredibly rich in fat,

roughly like 50%, and if you take a whole bunch of them and squish that

fat out and get it to cool down to room temperature, you get this.

This is cocoa butter.

Cocoa butter is just one of many different types of fat,

each with unique characteristics,

which create pure pleasure when teamed with the right food.

Imagine toast without butter,

frying without oil

or ice cream without, well, cream.

Fat transforms our enjoyment of food and for good reason.

Before agriculture, fat was a critical source of energy

to our ancestors.

So our brains may well have evolved to reward us with feelings

of pleasure when we ate it.

And we now know exactly where in the brain this pleasure is felt -

regions like the lateral hypothalamus and the amygdala.

We've even seen that the higher the level of fat in a food,

the more active these parts of the brain become.

Now, there's one national delicacy almost guaranteed

to fire up your brain -

Cornish clotted cream.

It's a whopping 60% fat, the creamiest of all creams.

But it may not have originated in Cornwall at all.

I've come to Afyon in Turkey

in search of the origin of clotted cream.

It's one of the richest, most melt-in-the-mouth dishes in the world.

But I'm also here to discover just why this type of fat has such

a powerful effect on our brains.

The fat I'm interested in is made from the milk of these animals -

water buffalo.

To make the creamiest fat, you need extremely rich milk,

and to make that, water buffalo

need to eat something pretty extraordinary.

These are the poppy fields that surround Afyon.

At the height of summer, the seed heads are harvested for the legal

production of opiate-based medicines like morphine.

What's left behind becomes fodder for the buffalo.

Hi there.

Along with hay, this is what these buffalo are eating.

It's what's left over when they've taken the poppy,

they've extracted the opium and sent it off to be turned into morphine

and other painkillers

and this is really what remains.

Now, there's not going to be any opiate left inside it but it's said

to be extremely nutritious

and the reason they feed it to buffalo is it's said

to add to the flavour, but particularly the sort of...

the richness, the fatness,

the oiliness of the milk.

There you go.

Oh, blimey!

The poppy is packed full of natural oils and fats and some of this

ends up in the buffalo's milk.

Let's give it a go.

HE GROANS

Nothing.

Sorry about that.

Yeah, OK.

HE LAUGHS

I think I'll leave it to you.

The milk produced by buffalo is extremely rich

and has twice the fat of cow's milk.

So here we go. That's the product of a bit of hard work - not by me,

I have to say.

This rich, oily milk will be turned into an ancient version

of clotted cream called kaymak.

-Merhaba!

-Merhaba.

This is where the magic happens, is it?

Milk has a very particular chemistry.

It's mainly fat and water,

which together form what's called an emulsion.

The fat is dispersed throughout the water in tiny globules.

When it's heated, some of the water is evaporated off,

leaving a higher concentration of fat.

These globules become sticky and some bind together to form

a delicate mesh on the surface.

It's now a matter of letting it stand and gently cooking again until

it's ready.

Now, this is a very traditional way of making clotted cream and,

in fact, it's pretty much how they make it down in Devon and Cornwall

and that is perhaps because there is a link.

It's said that the Phoenicians around 2,000 years ago

brought this technique from this part of the world.

They went to Cornwall in search of tin,

what they left behind was clotted cream.

So the great Cornish delicacy could have started life here in Turkey.

This is kind of the end product, right? You stick your hands in.

She's invited me to stick my hand in as well. OK.

I have washed my hands, I promise you.

So it's, erm, like sort of the finest soap.

You can imagine sort of, you know, washing in it almost.

It's got a very lovely sort of silky texture to it.

OK, so I think...

'Kaymak is 60% fat, three times that of single cream.

'The way it feels on the tongue drives our brains wild.'

So what is it that kaymak has that other foods are missing?

Why is it so much more seductive than, say, butter?

The way that kaymak is made obviously determines its structure

and its structure in turn will influence what it feels like

in my mouth, so let's give it a go.

Oh, it's very smooth and creamy.

I can feel it flowing across my tongue.

The ease with which something flows is also known as its viscosity

and that is something you can measure.

This machine is a rheometer.

It accurately measures viscosity at certain temperatures and pressures.

And viscosity turns out to be the secret behind why

kaymak is so good to eat.

What is really striking about this graph is the collapse here at around

24 degrees, when it goes from being sort of thick and solid and turns

into a liquid. We did the same test with another fat,

in this case it was butter and, as you can see there,

butter begins to change at around 24 degrees but it's a much more gradual

change and that may help explain why butter is not one of those things

you like to take out of the fridge and sort of wolf down.

Kaymak melts and flows more quickly over the tongue than butter,

making it feel smooth.

Dig in!

'And it's this smoothness that our brains respond to,

'via special receptors on our tongues.'

Some kaymak.

If you take a close look at your tongue,

you'll see it's covered with lots of little bumps called papillae.

On the surface of these papillae,

you have taste receptors, but you also have touch receptors.

Now if you eat something which is fat,

then that fat contains tiny little globules which are so small,

only a few microns across,

that your touch receptors don't perceive it as different particles,

they just see it as one thing, smoothness.

Since fat triggers touch receptors on the tongue,

you might think that the signals end up in the touch region of the brain.

And indeed they do.

But the signals also go to the area for taste so, oddly enough,

the brain perceives the feel, the texture of fat as a taste,

which helps explain why the texture of some fats is so important when

it comes to creating these wonderful feelings

in the pleasure centres of our brains.

Thank you very much. Bye-bye!

Chocolate, too, can drive the pleasure centres of our brains wild

with its creamy, high-fat content.

But until the 16th century,

we wouldn't have given it a second thought.

When the Spanish Conquistadores first arrived in the Americas,

they found the indigenous people drinking a bitter mixture

made from cocoa beans.

The Spanish thought of adding one more ingredient that would make for

something far more appealing.

And they were right.

That ingredient was lots of sugar.

The addition of sugar to this mix is so crucial

to our enjoyment of chocolate, because in nature

sugar and fat are very rarely found together,

at least in high concentrations.

Fruits like strawberries are packed full of sugar.

If you want fat, certain cuts of meat will give you a hefty dose...

..but if you want a mixture of both, and in relatively equal measure,

there's just one place in nature that that can be found.

It's only really in breast milk where you end up with this perfect fusion

of 50% of the calories coming from sugar and 50% coming from fat.

So our craving for chocolate goes back to the first moments of life...

..your very first meal.

And that craving stays with us.

If you think about almost all the foods that just drive people crazy,

you know, cookies, doughnuts, cheesecake, ice cream,

if you look at the recipes,

almost all of them have a rough 50/50 split in terms of calories

between sugar and fat. It's that golden formula that just basically

sends off all the pleasure signals in our brain,

making food just irresistible.

It's a comforting chemical composition that we biologically

are set up to love.

So what exactly are chocolate and other fat and sugar-filled foods

with that magic 50/50 ratio actually doing to our brains?

Why do these foods become almost addictive?

Even as I look at all this lovely fat and sugar,

I'm beginning to drool.

My own weakness is our very own version of kaymak...

..clotted cream at the heart of a cream tea.

I've even got a little bit of a shake.

Our desire to eat as something as delicious as a cream tea...

..and why we crave it over and over again has been mapped in the brain.

Mmm!

Now I'm getting sensory overload.

It releases a whole

host of flavours in my mouth.

There's also loads of things clicking off in my brain,

and I'll show you here just what's going on.

What's happened is the pleasure I get from cream teas

has activated an area here.

Because, just like kaymak, it all begins in the amygdala,

the area in our brain which is the core

of our emotional response to food.

It, in turn, triggers something called the reward pathway,

part of which is the nucleus acumbens.

This is where desire forms.

I like it, I want it, I want more of it.

The desire centre creates the motivation to eat again

by activating two other parts of the reward pathway.

This area here is where memories are laid down.

It's called the hippocampus.

Memories I'm building up from this occasion,

being here in a nice tea shop on a sunny day in London.

My brain is creating a strong memory of the pleasure of eating

a cream tea so I'll remember it in future and want it again.

This area of the brain is different,

it's more complex. It's the frontal lobe.

This area controls our behaviours and planning.

When the desire centre signals to this region,

it's reinforcing the sequence of behaviours...

..the exact procedure required to get hold of a cream tea.

Should you see any one of these things again,

you'll be reminded of how much you enjoy cream teas

and you'll know exactly what you need to do to get it.

It's your brain's way of motivating you,

ensuring that the pleasures you experience in the present

are repeated in the future.

Of course, many foods have an impact on the reward pathway.

But new research is revealing how one drink in particular can actually

magnify its powerful effect.

That drink is coffee.

Here in the UK, we get through 55 million cups each day.

Part of the appeal is coffee's active ingredient, caffeine.

And scientists are now close to understanding how caffeine boosts

our reward pathway by studying, not humans but, surprisingly, bees.

Alongside chocolate,

Peru is also a major producer of coffee

and I've come to see how this beautiful plant reproduces.

In the wild the plant relies on insects for its pollination

but therein lies a mystery.

It seduces pollinating insects,

looking for food, with the promise of nectar from flowers.

But it also needs to defend itself from pests, so its cells secrete

chemicals to keep other insects at bay.

Plants can't run away and hide from their predators,

so what they've done is developed a totally different

evolutionary strategy - chemical weapons.

So in the case of coffee, for example,

you have these seeds here which are packed full of caffeine,

which is toxic to insects in large doses.

It's found in its leaves,

it's found throughout the plant, but the weird thing is

it's even found in flowers and the whole function of a flower

is to attract insects, so it kind of begs the question

if something else is going on here?

Even though caffeine is toxic to insects in large doses,

there must be something else about

this chemical that insects find tempting.

Understand this and it might help us understand

why humans find coffee so tempting.

Professor Geraldine Wright of Newcastle University is attempting

to untangle this puzzle, with the help of her bees.

Bees are one of the highest forms of life on the planet.

They have evolved fairly sophisticated brains that allows

them to learn floral traits and associate them with food.

The bees are delicately harnessed to allow handling.

They're then fed a sugar solution.

Some will also be given caffeine

to see whether this affects their behaviour.

Coffee flowers produce a lot of scent.

They have a beautiful floral scent that's like jasmine.

And so in this experiment,

we were training bees to learn to associate a floral scent

with a food that contained caffeine.

First, each bee is given a puff of the floral scent...

..immediately followed by a meal of sugar solution.

Crucially, half the bees are also given caffeine

and the other half none.

The test comes 24 hours later.

This time, the bees only get a puff of scent.

Will they remember that yesterday,

the same scent came along with a meal?

First, Gerry tests the bees that haven't been given caffeine.

If they remember the association between scent and food,

they'll lift their mouthparts in anticipation of a rewarding meal.

Just 20% respond to the scent but the majority do nothing.

Next, the bees who'd had a caffeine fix with their food are tested.

Incredibly, 60% of these bees respond to the scent alone.

Three times as many bees who'd had caffeine remembered the association

of scent and sugar reward a day later

as compared to bees who had no caffeine.

It's a result which helps begin to explain caffeine's power.

A little dose of caffeine and nectar goes a long way to helping bees

to learn and remember the scent of flowers.

Caffeine itself is making the brain

believe that these signals are more intense.

Caffeine is amplifying the experience

the bees have with sugar when

they're eating and it's making it seem better.

The results we found regarding bee memory can be translated to people.

It's very likely that caffeine is affecting human memory in the same

way, via the same mechanisms, basically by amplifying reward.

So it begins to suggest that when we drink a coffee,

that pleasant feeling of the hot liquid is just made even better by

the caffeine, so we crave it again.

And if you add sugar or syrup or cream to your coffee,

then the caffeine will make this pleasure even more intense,

so you're even more likely to go back for more.

It could be that this is part of

what makes our daily cup so addictive.

Our brains learn to love the ritual of making or buying coffee.

We're like bees, buzzing around flowers,

seeking out that extra hit of pleasure each time we enjoy a cup.

Our relationship with food is complex

and the powerful human brain is very adaptable.

That also means we can learn to love some rather unusual foods.

We can acquire new tastes.

Food that is delicious for some is revolting to others

and that often depends on where you are in the world.

For example, brain.

Now as well as being a brain, this is also food, and here in Turkey,

a sheep's brain salad is something of a delicacy.

Now this brain is very small and that's because it comes from a sheep

and sheep don't have to make lots of complex decisions.

I like to think of sheep wandering the fields in the sunshine and

occasionally they'll stop and have a bit of a nibble.

When it comes to food,

the thought process goes something along the lines of,

"Grass, stop, eat."

You can guarantee that while our sheep here might have enjoyed its

meal of grass, it's never tried a cheesecake for pudding

or a bit of horseradish on the side.

And that's because its brain has a key difference to ours.

If I cut this open, you can see that in some ways,

it looks like a human brain, except that in a human this area here,

which is called the frontal cortex, would be much, much bigger,

and that's because it's where we make all our important

conscious decisions like where am I going to go on holiday,

do I really need that extra bit of chocolate cake?

The frontal cortex is in many ways the area of the brain that makes our

lives so much more rich and complex than that of a sheep.

It's our enlarged cortex that has led us to experiment with our food,

inventing numerous delicacies across cultures and cuisines.

And that's where it gets a little bit tricky.

I've never eaten a brain before but there's always a first time for

everything, so some lemon juice, a little bit of olive oil...

..and here goes.

Mmm, yum!

Aw, God.

Not at all what I expected.

I was expecting something a little bit

rubbery and this is actually more like a sort of strange jelly.

And not a lovely aftertaste.

I think this is an acquired taste and it's not one I plan to acquire.

Acquiring taste is something we excel at.

It seems that our brains are wired to enjoy the novelty in our food

and that we can learn to overcome disgust.

Sometimes, in the case of chilli peppers, even pain.

To investigate the powerful effect that chilli peppers have on the body

and brain, I've come to the largest market on the planet

where tonnes of chillies are sold every day.

I'm in Mexico, where humans first learned

to farm the chilli plant some 6,000 years ago.

The spicy flavour in chillies is

caused by this chemical called capsaicin.

I say flavour, but it's really like more of a texture,

almost a feeling and this is where it all is,

so everyone says it's the seeds that are spicy and that's not true.

It's this business here,

this white spongy layer that we call the placenta.

It's that bit and that's where pretty much all your capsaicin is manufactured.

These tiny little dots along there.

Each one of those is a gland that produces capsaicin.

And all this capsaicin has a very direct effect on a particular part

of our biology...

Something known as the TRPV1 receptor.

TRPV1 receptors are found in the mouth,

on the tongue and throughout the body.

Their purpose is to detect the sensation of scalding heat and raise

an alarm signal in the brain to protect the body from harm.

Purely by chance,

the shape of the capsaicin molecule happens to fit onto

the TRPV1 receptor like a master key in a lock.

This triggers the receptors to activate,

and they send a signal to the brain,

fooling it into thinking that the mouth is on fire.

Capsaicin has an almost unrivalled ability

to generate pain in our bodies.

So how did a potential food source

end up with this astonishingly powerful irritant?

To answer the question, I'm going to need the help of a hopefully

-friendly parrot.

-You look scared, James.

-I am very scared.

-Try not to be. You might get a bit closer.

Whoa!

No, I don't want to do this!

I'm going to give it to you there.

-Jesus.

-It's cos you're snatching it away.

I know, I know. Oh, and he nearly got me.

OK. There you go.

Have a look at that. OK.

What do you think?

You like that, don't you? Yeah?

In the wild, it's relatives of these guys, birds,

that are the key way that chilli plants disburse their seeds

everywhere and that's because birds

are completely immune to the effect of capsaicin.

It's like it doesn't even exist for them.

Birds do have a TRPV1 receptor,

but is a different shape, so no lock and key fit,

no activation and no feeling whatsoever.

So the chillies get their seeds spread on the wing

whilst being left alone by other animals.

But then came along an ape with a giant frontal cortex

that learned to love the burn.

Michael and I have come to a food and music festival here in Bristol...

..where we're going to compete in a chilli-eating contest.

We're taking on ten other brave souls...

..including a man dressed as a chilli and another dressed as a zombie...

-COMMENTATOR:

-Good afternoon, Bristol!

..to experience first-hand the effect that chillies have on our

bodies and our brains.

Welcome to our cathedral of pain and chaos.

I'm actually feeling slightly nervous.

I do quite like hot things and although this is not really

a competition, it is. I'd quite like to do better than you.

I grew up eating chillies. I've been using them since I was

eight years old, but famous last words.

OK, there's a good chance you'll beat me, then.

Bristol, please give a big round of applause to all the chilli contestants.

CHEERING AND APPLAUSE

The things we do in the name of science.

Good to go. Good luck.

The principle of the competition is simple, at each round,

the chillies will get hotter and hotter and the person

who lasts the longest wins.

Some very brave, stupid people.

This is the first chilli that they're going to get.

It is called a Dutch long chilli.

On my mark, three, two, one.

Eat!

The ferocity of a chilli pepper is measured in Scoville heat units.

This weighs in at 500 Scoville units.

The higher the Scoville number,

the more capsaicin in the chilli and more fiery in that becomes.

It's got a bit of bite to it.

There's a long way to go before we encounter the most ferocious chillies

that can reach millions of Scovilles.

So this is OK.

On my mark, three, two, one.

Eat!

These are chunky.

These have got a lot of moisture in, actually.

Savour it and enjoy them.

Three, two, one, eat!

That one went up the nose!

Oh!

Please give these guys a round of applause.

We've now consumed a considerable amount of capsaicin.

And all those capsaicin molecules are attaching themselves to TRPV1

receptors in our mouths...

Go on, get it down you.

..sending signals to our brains, making us think we are literally on fire.

My eyes are already beginning to water

and my pulse is shooting up.

This is the fight or flight response.

The fight or flight response normally occurs

when we sense a threat or danger.

The body responds with a shot of adrenaline.

The heart beats harder and faster.

Pupils dilate.

You breathe deeper.

And your arteries widen,

sending a flood of blood to your muscles to get them ready for action.

It's all accompanied by a rather more positive feeling that might

hold the key to why some people like this fiery sensation.

The thing is that when you eat a really, really hot chilli,

you also get an endorphin response which is one of the most natural

opiates. Sometimes you get it when you do exercise. But it's supposed

to be a feel-good hormone. I'm not sure I've got that yet.

It's part of the chilli's allure.

Endorphins are powerful painkillers,

released by own bodies and so should lessen the chilli's sting.

But they're also thought to induce a pervasive sense of happiness,

even a rush, which can be addictive.

Yes! Nicely done.

Three, two, one.

Eat!

How are you doing?

HE GROANS

Our fifth chilli is 15,000 Scovilles.

With our brain's pain centres in overdrive,

Michael and I need to dig deep to stay in the contest.

Oh, dear.

See you!

I can feel basically

the tears coming out, the snot is coming out

and I thought I was going to vomit for a moment there,

so I thought it's probably a good time to withdraw.

Ladies and gentlemen, please give Mr Michael Mosley a round of applause.

The best thing to soothe the burn is not water, but milk.

It helps neutralise capsaicin

because it contains something like casein.

Casein molecules are attracted to oily substances

like the capsaicin in chillies.

They surround the capsaicin,

preventing it from latching on to the TRPV1 receptors in our bodies

and it just gets washed away.

So if you ever encounter curry you can't handle,

don't bother with water, reach for the dairy.

Three, two, one, eat!

I'm still in the running, and on to the sixth chilli.

And this one is 30,000 Scovilles.

60 times hotter than the first.

The reason why psychologists think we like eating chillies

is there's a minor form of sadomasochism,

a bit like riding a roller-coaster.

And I can confirm that.

Driven by the human rush of excitement.

It's thrill-seeking, feeding our brain's desire for stimulation.

Honestly.

Ladies and gentlemen, please give James Wong a round of applause.

Excellent work.

Oh, that milk is good.

I can still taste it.

We still don't know why people have different tolerances to fiery foods

but we can speculate that people with thrill-seeking personalities

are more likely to expose themselves to the burn

and may build up a tolerance to capsaicin.

Out of 12 people, we finished 11th and 12th.

And the rest are soon dropping like flies.

Right, so next up, we have Thai red chillies.

Three, two, one, eat!

Oh, my goodness me.

These are naughty.

Jerry's gone.

The last two contestants have overcome intense pain

to reach the penultimate round.

They now face the infamous Jay's Red Ghost Chilli,

at a staggering 1.2 million Scovilles.

Too much for Steve. Drinking milk puts him out of the competition.

Rebecca has won.

Our love of chillies shows an experimental side to our eating habits.

Rewarded by endorphins and a rush of pleasure,

we've become culinary adventurers,

constantly seeking out novel food experiences.

It's even led us to consume a chemical that,

in its pure form, is frankly poisonous.

It comes in many guises.

It can pass right through the barrier which is supposed to protect

our brains and directly interfere with them.

It is, of course, alcohol.

This is red wine.

It smells rather nice, and I'm sure it's the product of years of hard

work and experience, but I'm not going to drink it.

I'm going to send it off to be evaporated.

Alcohol has a lower boiling point than water.

So, gently heating the wine in a rotary evaporator turns it into

a vapour, which rises and can be collected.

Alcohol is packed with energy.

Here it is.

Back again, smelling completely different.

And by now, it should be almost pure alcohol.

And if we dim the lights down, we should be able to see it burn.

Every gram releases seven calories of energy,

so drinking adds calories to your diet.

But energy is not why most of us drink.

Alcohol's popularity arises from what it does to our brains...

..which means pretty well every culture has invented its own tipple.

To show just how widely alcohol is enjoyed,

I've come to somewhere where they produce an extraordinary brew.

It's in northern Peru, and here the locals have improvised a unique way

to produce their own steady stream of alcohol.

These are the Chanka people,

they have been here as a group for over 700 years and, way back,

had the Inca for an enemy.

And throughout their history, they've made a drink called masato.

Like all cultures they use what's to hand, and for them

that's the root of the yucca plant.

Hi there.

Hello.

THEY TALK IN OWN LANGUAGE

Hi there.

I've joined them to reveal the lengths to which people will go to

in search of their own tipple.

Once the yucca roots are peeled,

they are boiled to soften them and then they are crushed.

THEY LAUGH

They are having a good laugh, I'm not entirely sure what it's about.

All yours. I'm hoping I'll be better at the next bit...

..when they add a crucial ingredient...

..spit.

More.

More!

THEY LAUGH

Yes, that's how it's done.

Apparently, this is normally just a female only activity.

I'm not sure

adding a bit of sort of Gringo male spit to it is adding to the flavour.

This may look absolutely disgusting but it's actually part of the process

because the saliva is actually an intrinsic part of the whole thing.

What happens is the saliva

in your mouth contains an enzyme called amylase

and this stuff is all starch.

What the amylase does is it breaks down the starch and releases

the sugars inside it.

If you've ever stuck a cracker in your mouth and left it there

or perhaps you've stuck some white bread in your mouth and left it

there, what you'll notice over a little while is

it starts to taste rather sweet,

and that's because the amylase in your mouth is breaking down starches

and releasing sugar. So you have to

stick it in, run it round, amylase springs into action.

And then,

you gob it out.

The point is to get some sugar.

Once you have sugar,

all you need to turn it into alcohol is a little fresh air.

That's because our atmosphere contains many forms of tiny

single-celled microorganisms called yeast.

When one of these yeast cells lands on the chewed yucca,

it starts to feed on the sugar and begins to multiply.

And they get the energy to do this from the breakdown of sugar.

The yeast starts digesting the sugars in the yucca.

In the process, each sugar molecule is converted into four smaller

molecules, two of carbon dioxide and two of alcohol, as waste.

The small size of the alcohol molecule

is crucial to our enjoyment.

Being small helps it pass through the barrier around the brain's blood

vessels and go straight into the brain itself.

Now, fermentation is at the heart of lots of the things we love.

Not just booze, but chocolate, yoghurt, and of course, bread.

Now, with bread, the product of fermentation that you really want is

not the alcohol but the carbon dioxide.

Because that's what makes it rise

and produces that lovely spongy texture.

There is a small amount of alcohol in the dough, but that gets

evaporated off when the bread is baked.

Yet in masato, it's all about the alcohol and it's beginning to build.

But there's a limit to how strong it can become.

Once the alcohol level increases to around 6%,

it becomes concentrated enough to poison many types of yeast, which die.

And that in turn slows the fermentation process.

And it's at this point it's ready to enjoy.

It's my last night and the villagers have invited me to eat with them.

So, with some trepidation,

I'm going to sample their unique form of yucca beer.

Right, OK.

So, moment of truth. I'm a little apprehensive.

Hm. It wasn't what I was expecting.

It's kind of got a bit of an alcoholic kick to it,

and it's quite bitter.

It's almost sort of yoghurty.

THEY SPEAK IN SPANISH

OK. You drink it pretty well every day, do you?

Todos los dias.

Muchas gracias. En ingles, decimos, "cheers".

Cheers? Cheers.

-Salud?

-"Salud", exactly.

It's not terribly alcoholic.

I'd guess it's probably about 4% or 5%.

But I suspect if you drink enough of it, you get fairly jolly.

After a few bowls, I'm starting to feel the effects.

When it gets into your bloodstream,

it hits your brain and there it really starts to do the business

because one of the things it does is it affects

a neurotransmitter called GABA and it actually...

I'm sorry, I'm slightly losing...

I'm losing the thread here.

What I'm trying to say is that GABA is a neurotransmitter or

chemical messenger that is present throughout the brain.

Normally, it regulates the brain's activity.

It's function is to act rather like a brake on brain cells,

stopping them firing at the wrong time.

You've got the GABA neurotransmitters

and what happens is the alcohol...

Alcohol interferes with the GABA system...

..by making brain cells more receptive to GABA.

The potency of GABA increases and so does the dampening effect

on the brain, switching off areas one by one.

At first, this can make you feel liberated, excited, amusing,

because the alcohol starts by switching off

the areas that control our inhibitions.

Yep. Life and soul.

These regions have brain cells with the greatest number of GABA receptors,

so they are most sensitive to the effects of alcohol.

The emotional regions of the brain are the next to be suppressed.

They have almost as many GABA receptors.

They are followed by your motor controlled region, and then memory.

What GABA does normally is it switches off parts of your brain,

I think it's that, but I've slightly forgotten...

Finally, if you are blind drunk,

you are left with only

the most basic parts of your brain still operating.

They have the least GABA receptors and fortunately,

they go on keeping you breathing and your heartbeat ticking over,

even when you're unconscious.

Thankfully, I am not at that stage tonight.

Alcohol has a dramatic and in many ways

a very addictive effect on our brains.

It is so addictive and pleasurable that humans will find just about

any way they can to make it,

even if all you have to start with is some yucca.

THEY SING

'The deep connection between our food and brain...'

Whoa!

'..is there for a reason...'

That's intense.

'It's part of our evolutionary story.'

We indulge our senses,

which, in turn, reward us with feelings of pleasure in our minds...

..keeping us coming back to the table for more.

Meanwhile, across the world,

food scientists will continue to delve into the chemistry,

physics and biology of our food, to try and understand how it works

on our bodies and on our minds.

And, all the while, our love affair with food continues to evolve.

And that's because we are constantly pushing the barriers,

looking for new ways to stimulate

our incredibly demanding human brains.

How does science change your view about what we eat?

Test your food instincts and find out more facts about food by going

to the website on the screen

and follow the links to the Open University.