We Are What We Eat 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 affect food has on us and our biology,

right down to the molecular level.

As a botanist, I'm 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.

Across the world, food comes in a bewildering range of shapes,

colours and flavours,

but there was a time early in our lives when things were much simpler,

when we lived and thrived on just one food.

Chances are this is the first food you ever consumed -

it's human breast milk.

Now, what's amazing about this stuff is that it contains all

the nutrients a baby needs to grow and thrive.

Fed on nothing but breast milk,

a baby will double in weight in just five months.

So how can this precious liquid provide everything a baby needs

to grow and prosper? To find out, I'm going to take it apart.

We start by putting 200ml samples, a few feeds for a new-born,

into a centrifuge.

A quick strain and the first ingredient in the milk is visible.

Now, this contains around 8g of fat,

about the same amount as you would find in a bag of crisps,

fat that is essential for building a baby's nervous system

and the smooth running of their brain.

What's left is this skimmed milk, which is mainly water,

but which also includes another vital ingredient.

I should be able to make it appear by adding a few drops of vinegar.

Now I need to filter it.

This is protein, essential for building a baby's body.

I'm left with a solution of vitamins, minerals

and one last major component.

Now I'm going to do something slightly weird

because I haven't tasted breast milk since I was a baby.

Surprisingly sweet, although I guess it shouldn't be surprising

because about 7% of that is made up of lactose, which is a sugar,

a form of carbohydrate,

and babies need carbohydrate because they need an instant source

of accessible energy.

So this mix of carbs, proteins, fats,

vitamins and minerals in breast milk is all a baby needs to survive.

The funny thing is that, as we get older, it doesn't really change.

They just come to us in different forms of food.

As adults, we're faced with a huge range

of different foods to choose from.

So how do we go about getting the right balance of fat, protein,

carbs, vitamins and minerals?

And which are absolutely essential for our survival?

Every morning, all over the globe, we wake up ready for food.

COCK CROWS

We rise with our blood sugar low and the same need - quick energy.

Be it toast, cereal, or rice,

it's little wonder that most of us turn to the same type of food

for that first meal of the day - carbohydrates.

Did I snore?

-No.

-OK, good.

Carbohydrates are fantastically diverse.

It's really sort of a catch-all terminology for a group of chemicals

that are made up of building blocks of sugar.

There are many different types - glucose, lactose and probably

the most exciting one, starch.

It's what plants use to store away their energies

in a concentrated format. Round here, it's usually found

in the form of a seed stolen from a grass.

Oryza sativa, better known as the rice plant.

Each seed is a grain of rice, a marvel of nature.

But rice doesn't give up its energy easily.

These terraces here in Banaue are called by some

the eighth wonder of the world.

The people who live in these mountains have been cultivating rice

for over 2,000 years.

-Hello!

-Hello!

'And today, it's my turn.'

I feel like Superman to be able to do this.

'As we work the terraces, we're burning calories,

'a measurement of energy.

'Even at rest, our body needs fuel to tick over and,

'just standing here, I'm burning about 100 calories an hour.

'But while working the fields, that jumps up to around 350.'

-You're tired?

-I'm waiting for my Asian rice farmer genes to kick in.

I don't think they work!

We get our energy from our food

and the carbohydrate-rich ones like the rice I had for breakfast

give us fuel more quickly than any other type.

The body breaks down long carbohydrate chains

into a simple sugar - glucose.

It's easily absorbed in the blood and transported around the body,

feeding our muscles and our organs.

Carbs are the rocket fuel in our diets.

Growing rice by hand requires a lot of energy.

So we have to be sure we get a lot more energy from eating it

than it takes to produce it.

I mean, even harvesting the stuff is labour-intensive.

And you can be burning over 400 calories an hour.

So, after six months of loving care and hundreds of labour hours,

you end up with this beautiful stuff - raw rice.

I still wouldn't call it a food, though.

All this effort begs the question - why do we bother with rice at all?

The reason why rice is such a phenomenally important food is the

sheer amount of energy that's packed into each one of these tiny grains.

And I can actually show you how much energy they have visually

but, first, I've got to break them open.

This stuff might not look very exciting,

but it's packed full of energy.

You can convert the potential energy that's stored in the rice grains

into heat and light energy just by doing this.

'Each puff is around 10g...'

I could do this all day! '

'..and contains around 35 calories of energy,

'all going up in flames.

'And almost all of it comes from carbohydrates.'

Now, our bodies might not do this in the exact same way

because we use complex biochemistry to do it.

And rice doesn't give up its energy without a fight...

..but we have discovered how to harness its power.

Even once fully processed, rice is essentially indigestible

because starch really stubbornly holds on to its energy -

until you do this.

Cooking is the game-changer.

The starch in the rice is made up of

two energy-giving carbohydrate molecules - amylose and amylopectin.

But their long chains are packed together,

making them mostly indigestible.

The combination of heat and water

has the power to break the tangled chains apart.

This chemistry is going on inside every cell.

The starch absorbs the boiling water and swells massively...

..until the moment when the cells burst open

and the digestible carbs erupt.

So turning rice into a food is incredibly energy intensive.

A cupful takes about 70 calories to produce.

But we got 35 calories from just 10g,

which means a cup of rice gives us back around 700 calories.

We get a whopping ten times more energy out than we put in.

And that's why rice, a cultivated river grass,

has become such an important staple in the water-rich tropics.

Where it's too cold or too dry to grow rice,

we in the western world have turned to another crop for our carb hit -

wheat.

Most of the wheat we consume comes in the form of bread

and this city is famous for one particular type of bread -

sourdough.

I've been doing this for 37 years.

The minute I touched dough,

I fell in love with it and thought, "This is what I want to do".

No matter if you're rich, poor, or anything,

you're making something wonderful for everybody.

It begins with unprocessed wheat flour...

..a bland, tasteless powder that, if cooked, would set like concrete.

To turn it into a tasty food,

Fernando Padilla employs an army of microbes.

These microbes live in something

affectionately known as the mother dough.

This is where she lives, as you can tell. We say, "Mother dough lives here".

We're going to put an address here.

I'm carrying a piece of history here.

'The mother dough is a mix of water and flour,

'more commonly known as a starter.'

Inside it, a community of live yeast cells and bacteria thrive.

But this is no ordinary starter.

It's reported to be the oldest in the US.

And this goes back to 1849?

Imagine, over 165 years ago, it was the same dough.

A tiny piece of this dates back to the same family.

This starter was apparently created by French immigrants

during the great Gold Rush.

Inhale.

Oh, God!

That's all the sweetness of the flour being fermented.

It creates this alcohol flavour, but it all evaporates.

-You see how strong it is?

-I was expecting something nice!

This little thing is going to give us 400 loaves of bread.

Let's bring it out.

'Every day, half of the mother dough is fed with flour and water.

'Then it's locked away overnight, where it regenerates,

'doubling in size.' Good night, Mummy.

See you tomorrow.

This is 200lbs of flour here.

'The other half of mother will be used to create over 400 loaves of

-'of delicious, fresh bread.'

-We should have worn the apron.

Adding water activates enzymes in the flour.

This in turn starts a complex biochemical cascade,

which begins with starch in the flour

turning into a sugar called maltose.

Mix it for ten minutes.

Bacteria from the mother dough now feed greedily on the maltose,

breaking it down into glucose.

The bacteria have begun to digest the flour for us.

You hear that? When you hear the dough popping...

Pop, pop, pop.

It's saying, "I'm ready, get me out of here".

'If we baked it now, this would turn out as flat as a pancake.'

Why is mine not looking like yours?

-Now we just fold it over.

-Yep.

'Fortunately, another group of microbes will use

'some of the glucose to transform the dough.'

OK, this is dried yeast.

Doesn't look incredibly exciting, does it?

But every single grain there contains thousands of these

single-celled organisms and they're held currently

in a state of suspended animation.

I am about to bring them back to life.

To do that, they need food and water.

So I'm going to add sugar and then water...

and now I add the yeast.

If the yeast cells are still alive,

they'll produce a gas which passes through the pipe to the test tube.

Those yeast cells are springing back to life,

and they're going to get stuck into that sugar.

So it's working. You can see the bubbles being produced.

They're being created by the yeast gobbling up the sugar

and producing carbon dioxide gas, which you can see bubbling up.

And it's this reaction which is absolutely key

to producing a nice, fluffy loaf.

With carbon dioxide bubbling through his bread mix,

Fernando must now stop the gas escaping.

To do that, he alters the chemical structure of the dough

by a process called kneading.

I'm not an expert baker at all,

but I know the secret to making good bread is

making really sure you knead it thoroughly.

When we knead bread, we're forcing two proteins inside the flour,

gliadin and glutenin, to form bonds, creating a tough new substance -

gluten.

And this is where the art of bread-making comes in.

If you don't knead enough, you won't create enough gluten in your loaf,

so the gases will escape and it won't rise.

But get it just right, and the effect on the loaf is magical.

As it rises, its volume more than doubles as the yeast consume

the glucose and as they blow bubbles inside their gluten home.

The bacteria also produce a small amount of lactic acid

and, with no added sugar,

the acid gives the loaf the distinctive tang of sourdough bread.

Baking then seals the air pockets and, thanks to the microbes from

the mother dough, we end up with a carb-rich, light, fluffy loaf.

Whoa! Wow.

-How many loaves is that?

-This is about 100 loaves of bread.

Perfect.

Mmm. It's incredible.

Sourdough used to be one of the most popular forms of bread,

until it got displaced by cheap, mass-produced stuff

and that seems like a shame because it's tasty and it's also healthier.

It hasn't got added sugars and the acid in the bread means

you're much better able to absorb the minerals and vitamins

that are locked up in the flour.

In fact, I think I'm going to try baking some when I get home.

From the east to the west, by unlocking the secrets of rice

and wheat, our ancestors made the indigestible digestible.

As a result, these foods became the staples

that feed our towns and cities.

Historically, carbs were the foods that fuelled our civilisations,

a cheap and ready source of energy.

Energy keeps us moving, but it's protein that builds us.

Your body makes at least 250,000 different types of protein,

molecules which are needed to make everything from hormones

like insulin to the muscles that power you.

To create all these different proteins,

you need to eat plenty of protein, around 50g a day.

And one of my favourite sources of high-quality protein is eggs.

So I want to take one apart, see just what it is that I'm eating.

Right, I'm just going to prise off a little bit of shell,

and there it is. As you can see, it's hard, crystalline,

made up mainly of calcium carbonate.

Here, magnified over 2,000 times,

you can see the surface of the shell is covered in lots of tiny holes,

there so a developing chick can breathe.

Each hole is formed over a gap in a lattice of protein

that the shell grows over.

Surprisingly, this membrane is partly made from a tough protein

called keratin, the same stuff our hair and nails made from.

It protects the contents of the egg from bacteria and dust.

Inside, the white, or albumen, is a mix of water and 11% protein.

But it's the egg yolk where most of the goodness resides.

It's got minerals, vitamins, some fat, some cholesterol,

but it's also got 17% protein.

The fact that you find protein in the membrane, the white,

AND the egg yolk, shows you just how important protein is in us.

It's responsible for everything,

from running your immune system to carrying oxygen around your body.

And eggs are a really beautiful source of protein,

because almost all the protein there,

apart, obviously, from the shell, can be readily digested.

But, once you've eaten it, where does the protein from your food go?

Mexico City, home to a population of one of the highest consumers

of eggs on the planet.

And it's also home to the Lucha Libre.

BELL RINGS

When it comes to wrestling,

Mistico, El Santo and Shocker are all household names.

The way you look in the ring is very important.

In my case, I don't wear a mask

because they call me "El senor mil por ciento guapo",

which means "1,000% handsome".

I've been wrestling for 22 years professionally.

My dad used to be a professional wrestler, too.

He taught me mostly everything I know

and he taught me how to eat, too.

To build and maintain his impressive physique,

Shocker needs to eat a lot of protein.

To be a wrestler, you've got to have good nutrition.

If you don't eat, you don't grow.

In the UK, on average, we each eat around four eggs a week.

The average Mexican eats seven,

but Shocker puts away an incredible 50 every week.

The eggy proteins are needed because he trains so hard every day.

With each stretch and lift,

he is tearing the fibres deep down in his muscles.

This triggers his body to repair them.

Enzymes deep in his stomach and intestines break down the protein

in his food into their individual building blocks,

molecules called amino acids.

These enter his bloodstream and travel to where they are needed.

And, for Shocker, the amino acids join together to build the proteins

he needs to make bigger, stronger muscles.

I like my eggs in different ways.

I like them a la Mexicana.

They come with tomato, onion and chilli.

I like them rancheros,

tortilla under, sunny side up.

The way we prepare eggs makes a massive difference

to how easily we can use the protein they contain.

Contrary to popular belief, eat eggs raw

and we only benefit from about half the protein.

Cook them and it's a very different story.

It fundamentally changes the proteins in an egg.

You can see it happening.

If you really want to play around with the texture of the eggs,

you could invest in a water bath.

That way, you can control not only the time,

but also the temperature you cook the eggs at.

This is a raw egg and, as it slowly cooks, it changes.

Over here, you can begin to see some of the egg white is setting.

The protein in it is denaturing, meaning it's easier to absorb.

The longer eggs cook, the more the protein fibres denature.

The protein molecules literally unfold.

That's what's happening when egg white transforms into a gel.

These cooked egg whites aren't simply more pleasant to eat,

the untangled protein molecules also make it easier

for Shocker to absorb the protein his body vitally needs.

When you work out a lot, when you do a lot of exercise,

you start building up and you start making your food into muscle,

all different kinds of muscle.

Relaxed muscle.

Shocker's success in the ring is built entirely on the way he trains

and how his body uses the amino acids,

the building blocks of every protein,

to repair his muscles.

People like champions. We don't like losers.

You've got to look good. You've got to win.

BELL RINGS

Although we're made up of around a quarter of a million different

proteins, those proteins are comprised of just 20 amino acids.

The amazing thing is our bodies can just manufacture 11 of those,

but that leaves nine and we call them the nine essential amino acids.

We've evolved the cellular machinery

to produce all but these nine essential ones.

Those, we must get from our diet.

But this isn't always easy.

Eggs, fish and meat contain all nine essential amino acids,

but there are plenty of foods that don't.

To survive, we have to carefully mix and match what we eat.

Look at this. This is real Aztec gold.

For millennia, corn has been the staple crop

throughout pretty much the whole of Latin America

and that's because it's just packed full of the good stuff.

It's bursting with carbs, vitamins and fibre,

but crucially, though, it's missing two essential amino acids -

lysine and tryptophan.

But in this part of Mexico,

they've found an ingenious way of eating corn to get all the

amino acids they need and it's a rather surprising local delicacy.

I've always wanted to see it in the field.

You get these massively swollen ears of corn

and, when you split them open,

you can see the deformity that lies beneath.

Huitlacoche has been called "food of the gods",

but it looks like something from a horror movie.

It too is lacking essential amino acids, but eat this

with regular corn, and you get all the amino acids you need.

This is created by a pathogenic fungus

and it's a debilitating disease on maize plants around the world,

but only in Mexico do farmers open this up and get really excited.

This fungus begins as nothing more than a microscopic spore.

Carried on the wind, just one could infect an entire crop.

It germinates and sends out branches

that pass throughout the ear of corn,

where it affects every kernel, creating the swollen tumours.

Other countries would torch these infected fields, but not here.

What time is it now? 6.30 in the morning and in full swing.

Huitlacoche has become a delicacy,

served up in the best restaurants in town.

It's crazy, no?

At market, infected corn is worth 50% more than just regular corn,

so master chef Lalo Garcia arrives early to ensure he gets

the pick of the bunch.

-This is where I buy the huitlacoche.

-Wow.

-Look at that.

And the smell. The smell is amazing, that of earth.

It's why I really love this product.

It's amazing that earth still produces this, this type of beauty.

So we have a little olive oil here. Onions. We add our huitlacoche.

We're going to make a very basic salsa to go with our huitlacoche.

You'd never know to look at it,

but huitlacoche has the most amazing flavour.

It's kind of like black truffles meet shiitake mushrooms,

with that savoury volume whacked up.

Smoky, rich. It's got to be the world's best comfort food.

And eaten with corn tortillas,

I get my hit of all nine of those essential amino acids.

But the Mexicans aren't the only ones

to pull off this classic combination.

From the British favourite of beans on toast...

..to the Indian Holy Grail of rice and dhal...

..or the Italian staple of beans and pasta, across the globe,

we've invented combinations of pulses and beans mixed with grains

to give us all nine of the amino acids we desperately need.

We've instinctively become expert nutritionists,

hunting out exactly what we need from our food.

And no nutritionist would recommend a diet that didn't have some fat.

Whether you get it from meat, fish, nuts or vegetables,

fat, like protein, is essential for health.

Now, different foods have different forms of fat.

We've got olives, walnut, avocado.

Most of these fats are liquid at room temperature.

The odd one out is this one, which came from the beef.

It's solid at room temperature.

And the reason there are so many different types of fat is because

there are so many different types of building blocks for fat.

Each fat is in turn made up of something called fatty acids.

Complex fat chains are built by assembling

these smaller units of fatty acids.

Taking a close look at the fat in a piece of salmon

shows just how many fatty acids there are.

I'm mashing it up with some acetone,

stuff more commonly used to remove nail varnish.

This won't add to the flavour, but it will help separate out the fat.

There's a lovely layer of pink fat right there on the top.

Some fancy kit then reveals what I'm looking for.

You can see lots of different peaks

and each of these peaks represents a different fatty acid.

These fatty acids are essential to the smooth running of our bodies.

Eating salmon is a great way of getting hold of them.

But we are so dependent on fat that we've evolved cellular machinery

to build most of the fatty acids that might be missing from our diet.

There are two types, however, which your body cannot make.

They are omega-6 and the rather more elusive omega-3.

These we have to get from food.

Omega-6 is easy - there's plenty in vegetable oil.

Omega-3 is rarer. It's found in oily fish, like salmon.

But where else can you find it?

We're going roaming. We're looking for the cattle now, are we?

We are. It can take some time.

These are Highland cattle.

There we are, look. There's a cow away down there.

They're really well adapted to life in Scotland.

And though they sport the longest hair of any cow,

that's not what makes them special.

What marks these cattle out is that, unlike most cattle,

their meat is rich in elusive omega-3.

They look like really large dogs with horns!

Iain MacKay looks after just 50 cattle.

They're free to roam over a vast expanse of wild moorland.

Hi, gang.

The type of breed we've got here utilises this ground.

They have a massive stomach and they can take on a huge amount of

this roughage and then just go, lie down, and digest that.

And it's this natural environment that provides the omega-3

that we can't live without.

In fact, it is absolutely vital for building and maintaining

my favourite organ - the brain.

Surprisingly enough, a brain is half fat and, of that fat,

a quarter is made up of omega-3.

All this omega-3 forms the connections between every nerve cell

in the brain, cells which send and receive electrical impulses

from the brain's 80 billion other cells.

Low levels of omega-3 have been linked with depression and anxiety.

Fortunately, there's a ready supply of the stuff

scattered throughout this particular landscape.

It's found naturally in the oils in the grass.

But the highest dose can be got

from a delicious mouthful of Highland clover.

Magnify the clover 600 times

and you'd be able to see microscopic globules of omega-3 fat.

The cattle face the same challenge as us -

they have to get their omega-3 from their diet.

It matters what they eat.

Grain contains very little omega-3,

so factory farmed meat is lacking in this vital fatty acid.

But these cows get their fill from grass and clover. Once eaten,

the essential fatty acids enter the cells in their bodies...

Look at that!

..making this grass-fed steak far higher in omega-3

than beef intensively farmed and fed on grain alone.

Looks good.

Both omega-3 and omega-6 are vital for life, but it's a balancing act.

Too high a ratio of omega-6 to omega-3 has been linked to a whole

range of inflammatory diseases, from type two diabetes to arthritis.

And a recent US study found that it wasn't unusual for there to be

25 times more omega-6 than omega-3 in people's diet,

most of it coming from the vegetable oil used to cook fast foods,

like burgers, chips and cookies.

And as omega-6 is so easy to get, it means we really do

have to concentrate on getting enough omega-3.

So keep a look out for good sources of omega-3, like beans,

salmon, mackerel,

and grass-fed beef.

In a macabre sort of way,

I like the fact that I've met this cow's relatives.

It had a happy life and it didn't travel very far to get my plate.

I also really like the fact that it's rich in omega-3.

And it is incredibly succulent.

Most of the nutrients we require are found in the carbs,

proteins and fats hidden inside every meal.

But not quite all.

Although only needed in tiny amounts, we need to

get a constant top-up of vitamins and minerals to keep us healthy.

And there is one mineral-rich food we rely on from birth -

milk.

Here in the Rhodope Mountains of Bulgaria,

people are 30% more likely to live to 100 than people from the US.

So could it be their diet that's helping them live so long?

Well, what unites them is the amount of milk they consume,

rich in a mineral that our bodies can't make -

calcium.

Absorbed from food and passed from our gut into the bloodstream,

calcium is transported to where it's needed most -

our bones.

We're constantly rebuilding our skeletons.

And to do that, we have to keep eating calcium.

And the amount we need increases as we get older

because we just don't repair our bones as easily.

Each morning, Dobrina sets about a daily food ritual

which might hold the key to her family's long, healthy lives.

SHE SPEAKS OWN LANGUAGE

You must have much better technique than me

because there's nothing coming out here! I could be here all day.

Milk, be it human breast or from the cow,

is a fantastic source of vitamins and minerals.

We removed all the fat and the protein

to see just what the other constituents were.

And we found this incredibly rich,

chemical soup of all sorts of vitamins and minerals that are

floating around here. I want to get out one thing that's left in there.

After warming to 40 Celsius,

we added a salt solution to kick out what I'm looking for.

A suction filtration then gave me this gungy stuff.

That is calcium phosphate.

It's what your bones are made out of, so it's essential to human life.

But, for some of us,

getting enough calcium from milk is harder than you might think.

By the age of five, some people lose the ability to digest lactose,

the sugar in milk.

70% of African-Americans are thought to be lactose-intolerant,

80% of southern Europeans, but only 5% of Brits.

It's because, over the centuries, cultures that raise dairy cattle

adapted and developed the ability to digest lactose,

while cultures without cows didn't.

And that's a lot of people who can't drink our main source of calcium.

But we have learned to unlock the chemistry of milk.

For people who can't digest lactose,

drinking milk can turn their stomachs

and that's because a gene that triggers the production of an enzyme

called lactase has been turned off.

Now, lactase would normally break down lactose and, in its absence,

your body's reaction to the lactose can irritate your gut,

can make you feel really sick and, as a consequence,

it eliminates this ridiculously rich calcium source from your diet.

But long ago, these mountain people discovered

a bacterium that thrives on lactose, turning milk into yoghurt.

And, every day,

Dobrina carries on this family tradition making yoghurt,

beginning with boiling the milk.

What it does is effectively sterilises the milk, giving you

a clean slate until you're ready to add the bacteria that you want.

Oh, yeah. Perfect!

Just the right amount.

The curious thing is quite a lot of bacteria actually also have

a problem breaking down lactose, except for a few strains

and this is one of them here, a culture of Lactobacillus Bulgaricus,

otherwise known as yesterday's yoghurt.

I think what I do is I just pour it in here.

Is that what I do?

Oh, wait, no.

SHE SPEAKS OWN LANGUAGE

OK. I take this, I put in there...

SHE SPEAKS OWN LANGUAGE

-..and then I pour it in?

-No.

No? More?

SHE SPEAKS OWN LANGUAGE

OK, and I stir it. And then I pour it in?

OK.

Once the microbes are added,

they multiply as they feed on the lactose in milk,

producing the lactic acid which is vital to making yoghurt.

This exact process has been happening over and over again

for potentially thousands of years.

A lid on to keep any of the bacteria out

and all we're doing now is insulating the milk,

to keep the heat in, because the bacteria have a narrow window

of when they're active in terms of temperature.

SHE SPEAKS OWN LANGUAGE

Three hours?

No. Yes?

SHE SPEAKS OWN LANGUAGE

Three hours and we're eating? OK, I can do that!

I think it's back to Bulgarian school for me.

As the mixture becomes more acidic, the milk proteins clump together,

creating a soft, tangy curd - yoghurt.

Look at that, is that what we made?

SHE SPEAKS OWN LANGUAGE

Look at that proud smile!

Let's open that up.

You doubted my ability.

Look at that, it was so simple.

You can tell me what Bulgarian yoghurt tastes like

made by an English guy.

HE SPEAKS OWN LANGUAGE

It's really good!

Oh, thank you! That's lovely.

There's been this amazing transformation

in only a couple of hours.

The bacteria have broken down a large proportion of the lactose,

which means the whole mix is so much more digestible,

potentially even for people with a lactose intolerance, and that means

you get more calcium-rich deliciousness back in your diet.

Mmm.

Just 300mls of yoghurt will give you

nearly half your daily calcium needs.

But eating plenty of this vital mineral won't automatically mean

that our bodies can use it.

There's a final bit of chemistry necessary to lay down

and replace bone.

To do that, we need the help of vitamins.

Now, these are strangely hard to classify.

Vitamins are molecules that in many ways are best defined by

what they're not. They're not minerals, not fatty acids,

not amino acids, but they are absolutely essential,

albeit in very small amounts.

Magnified over 1,000 times, a beautiful world of crystals appears.

Our bodies use these vitamins as life-support

for many of our bodily functions.

Vitamin C is abundant in citrus fruits.

It strengthens blood vessels and gives skin its elasticity.

And there are eight different types of B vitamins.

B6 is found in nuts and does everything from

keeping our nervous systems running to processing those amino acids

into proteins that we need to repair muscles and organs.

Vitamin E - that we get from foods like avocado.

It acts as an antioxidant

and protects our cells from damaging chemicals

that are formed when we extract energy from food.

The vitamin A we get from carrots keeps our eyes healthy

and helps us fight infections.

And leafy greens supply us with vitamin K,

helping our blood to clot.

And the only way we can absorb calcium is with the help

of another vitamin - vitamin D.

The key to getting our daily dose of vitamin D is to get enough sunlight.

When sunlight reacts with cholesterol in our skin,

the result is the vitamin D molecule.

But here, high up in the Bulgarian mountains, and places far from

the equator, like the UK, year-round sunshine is scarce.

But there is a way through food that Mr Baklarev and his family can get

the vitamin D they need all year round.

Surprisingly, we've discovered that mushrooms

are a potential source of vitamin D.

Just like us, they need this vitamin to survive

and they use it as a protection from the sun's harmful rays.

How's that? Is that good?

Yeah? A-ha!

'Sunlight falling on a mushroom turns it into a vitamin D factory.

'They use a chemical similar to cholesterol called ergosterol...

'..which reacts with sunlight to make vitamin D.'

There's something miraculous about what we're doing here because

these mushrooms that are freshly picked from the dark forest floor

don't really contain that much vitamin D.

But putting them out in this intense UV light

and the mushrooms, which are still alive,

start to react by churning out that vitamin D.

And if you put them gill side up,

the surface area exposed to the sun increases...

..and they produce even more.

Just a few hours out in the sun and a couple of portobello mushrooms

will give us our daily dose of vitamin D.

Dry them and it stays locked away in the mushroom for up to a year,

a tasty way of getting vitamin D through those dark winter months.

This is amazing! I love this stuff.

You've got bread with cheese, yoghurt, a yoghurt drink.

There's no lack of calcium here.

And the vitamin D in these lovely mushrooms

allows our bodies to absorb that all-important calcium...

..sending it through the bloodstream

to cells called osteoblasts in our bones.

These creep through the skeleton, laying down calcium-rich bone.

This constant renewal protects us against diseases linked to ageing,

such as osteoporosis.

It could be a key factor not only to a healthy life, but also longevity.

So there are loads of factors at work,

but I can't help thinking that with air like this,

running around every day, home-made food,

and talk about a tonne of calcium - it can't hurt, can it?

We've found the foods we all need to keep us ticking over.

Day-to-day, meal-to-meal, we get much pleasure from the food we eat.

The smells, tastes, colours and textures delight us.

But what I think also really adds to that pleasure is understanding

the hidden biochemistry at work.

It helps us appreciate our food

and it also means we're able to make the most of the ingredients

hidden inside every delicious mouthful,

ingredients which nourish not just the body, but also the mind.

So if you're adventurous with food and you try a bit of everything,

not only are your senses rewarded, your body has a greater chance

of getting hold of all of those essential molecules

because, ultimately,

our bodies and everything we are comes from our plates.

'Next time, we explore the boundaries of taste...'

They are irresistible.

'..we revel in the sumptuous food that dazzles our taste buds

'and excites our noses...'

HE LAUGHS

'..as we discover how good taste is all about survival.'

How does science change your perception of food?

Find out how instinctive you are and learn even more about what you eat.

Head to the BBC website onscreen now

and follow the links to the Open University.