Very intriguing reason you can’t resist cakes

And why we can’t say no to lattes or smelly cheese, by Dr MICHAEL MOSLEY

Like so many who trained as doctors, i learnt very little at medical school about nutrition. So i was thrilled to be asked to make a TV series where i would learn all about the hidden chemistry of food and what it does to our bodies at a molecular level.

As part of the series The Secrets Of Your Food, i went to the country’s leading food science laboratories to deconstruct our favourite foods to find out exactly what’s going on when we eat them . . .

WHY IT’S SO HARD TO DENY OURSELVES CHOCOLATE

COCOA beans are 50 per cent fat, while Cornish clotted cream is 60 per cent fat. Why do we find this almost addictively delicious?

Partly it’s to do with the way the creamy viscosity of chocolate and cream melts on the tongue, feeling smooth. Special touch receptors on our tongues detect this — texture is thus effectively a taste, which prompts wonderful feelings in the pleasure centres of our brains.

But crucial to this enjoyment is the sugar added to make chocolate and found in cream.

in nature, fat and sugar are rarely found together — except in breast milk, where we find the ratio of two parts sugar (in the form of lactose, or milk sugar) to one part fat as well as the same viscosity that we love in chocolate and cream. (For the TV series, i tasted human breast milk and found it surprisingly sweet.)

in other words, we are primed to like these foods because they are like our first food — and as we grow older, our taste for this mix of carbs and fats does not really change.

The influence of the first food we ever ate sets the pattern for what is to come and for what kinds of food we will like in future — even if it’s not as healthy as breast milk.

You will find the same perfect ratio of carbs to fats found in breast milk in many foods we can’t resist, such as biscuits, cake and crisps. Manufacturers have exploited this golden formula to hook us on to their products.

The mix of fats and carbs activates an area in the brain called the amygdala, which is at the core of our emotional response to food. it also targets the nucleus accumbens, the brain’s centre of desire. This creates the motivation to eat it again.

The formula also activates the memory area of the brain — the hippocampus — to make you remember everything about the experience and the frontal lobes, which control behaviour and planning — so you can do what’s needed to recreate the experience again.

BEANS ON TOAST’S A PERFECT MEAL

ACrOSS the globe, humans have instinctively combined beans and pulses with other foods to create nutritious meals, whether it’s beans on toast, dahl with rice or beans and pasta (the classic italian dish, pasta e fagioli).

What’s driven this? it’s quite simple really.

Our bodies need something called essential amino acids to build protein. Our bodies can make most of these amino acids, but there are nine we can only get from food. And while you can get all nine from meat, most plant sources are missing at least one or two of them.

For vegetarians and people who want to cut back on meat, there are ready answers in the shape of time-honoured recipes.

By instinctively creating traditional recipe combinations of beans and pulses mixed with grain, our ancestors — perhaps driven by a lack of meat — invented ways to get all nine additional amino acids from plant sources.

PLEASURE OR PAIN OF HOT CURRIES

Our large brains have enabled us to acquire new tastes and learn to love foods that appear to harm us — such as chillis.

Chilli contains capsaicin, which triggers a pain receptor in our mouths and bodies called TrPV1. The receptor makes the capsaicin feel like scalding heat and sparks our ‘fight or flight’ response, which triggers the release of powerful painkilling substances called endorphins. These can also induce a natural high, which is why chillis are painful and pleasurable.

Surprisingly, the hottest part of the chilli is not the seeds, but the placenta, the white spongy ridge down the inside of the fruit.

Cut out the placenta to make your chillis less fearsome. if your curry’s still too hot, drink milk.

Casein protein molecules in milk are attracted to oily substances in capsaicin molecules. They surround them, preventing them locking into our TrPV1 receptors and washing them away.

WHY A SMELLY CHEESE IS SO GOOD

ePOiSSeS is one of the stinkiest cheeses in France. The bacteria with which it is made give off sulphur-based compounds that are related to those found on sweaty human feet.

When you inhale it, the smell stimulates receptors that can make you think ‘ugh!’. But when the cheese is in your mouth, the aroma compounds go into the back of your nose and smell different. This is because we then experience it through a mechanism known as ‘backward smelling’, where aromas waft from your mouth back through your nasal cavity, triggering smell receptors.

Your brain combines the creamy taste on the tongue with the smell, and dramatically changes your experience to pleasure.

The resulting flavour seems sensational — sharp, warming and comforting. For the full effect, always eat the rind. it’s where most of the smelly sensations lie.

MILK MAKES YOUR COFFEE ADDICTIVE

We drink 55 million cups of coffee a day in Britain. Why the attraction? Ask bees. research shows that the dose of caffeine from feeding on the flowers of coffee plants boosts their ability to remember the flowers’ scent — so they know to come back.

it also amplifies the bees’ positive experience of the sugary nectar.

Caffeine likely affects human memory by similarly amplifying the sense of reward: it makes us crave it again.

it may also make the experience of having sugar and cream with your coffee more intense. They make coffee still more attractive, and make us love the ritual of buying and drinking it.

YOGHURT MAY BOOST LIFE SPAN

There is a mountainous region in Bulgaria where people live unusually long and healthy lives.

This may be partly due to their diet, specifically the yoghurt they eat, which makes up a large part of their nourishment. The bacteria in the yoghurt, lactobacillus bulgaricus, is associated with reducing the inflammation in the gut and body that may cause problems such as heart disease and cancer.

You don’t necessarily need Bulgarian yoghurt to get such benefits. Local shop bought ones will help. Studies have linked many other full-fat, live bacteria natural yoghurts to improved health.

LOVE SALT? BLAME FISHY ANCESTORS

Our love of salt is due to our ancient biology.

Life seems to have arisen in the oceans, including the earliest cells. it follows that as these cells formed they trapped sea water inside them. To this day, salt remains vital to our cells’ function.

The movement of trillions of sodium ions in our brain enables us to think, move and sense the world around us.

Salt also interferes with bitter taste receptors in our mouths. To demonstrate this, try adding salt to coffee — it banishes the bitter flavour. This ability to make food

more palatable gives salt its powerful attraction.

The sodium ions also work on our taste buds. We have a salt receptor in our mouths that is constantly on the look-out for sodium in our food. It’s not ideal for our blood pressure, though.

STRAWBERRIES HELP YOU TO CUT SUGAR

STRAWBERRIES taste sweeter than blueberries, but contain half the sugar.

We think of them as very sweet because they trick the brain. The secret is in their smell. It contains 36 chemicals that boost our taste sensation and fool the brain into thinking that we are getting a lot more sugar than we are.

HOW TO TURBOCHARGE YOUR MUSHROOMS

WE GET most of our vitamin D, needed for healthy bones, from the sun’s effect on the cholesterol in our skin. But in the UK, yearround sun is scarce. One trick to boost our levels is to expose mushrooms to sunlight before eating or cooking them.

Mushrooms use vitamin D to protect themselves from the sun’s harmful rays. Exposing them to light turns them into vitamin D factories. They contain chemicals similar to cholesterol, which react with sunshine to make vitamin D.

The trick is to lay your mushrooms gill-side up on a sunny windowsill or in the garden for half an hour. This will dramatically increase their vitamin D content.

THE BITTER VEG YOU SHOULD LEARN TO LIKE

MOST poisons found in nature taste bitter, so we have 20 times more bitter receptors on our tongues than we do for sweetness. They are there to save our lives.

The potato used to be a bitter, poisonous plant — a relative of deadly nightshade — but descendants of the Incas in Peru transformed it into a life-giving staple through generations of cultivation.

But avoid green potatoes — they’re not only bitter, but can be poisonous. They’re green because of exposure to light, which may have caused them to develop a high level of toxins called glycoalkaloids.

Some veg have evolved bitter tastes as a defence against predators, but they are, in fact, the opposite of poisonous.

Brassicas — nutritious greens such as broccoli, sprouts and cabbage — use this trick. Most of us learn to enjoy them because we know they do us good, though often we can’t stand them as children.

IS BEEF THAT’S GRASS FED BETTER FOR YOU?

OUR bodies have evolved mechanisms for creating fats we need in our bodies. But there are two we can’t make: omega 6 and omega 3. These we must get from food. There is plenty of omega 6 in vegetable oil. Omega 3 is rarer, but it is vital for our brains.

Oily fish such as salmon and mackerel can contain plentiful amounts of omega 3. Seacaught salmon are rich in it, because they get it from eating omega 3-rich seawater algae. But freshwater salmon contains very little. When the fish migrate into rivers, they lose their algae diet.

A rugby team nutritionist told me mackerel is a much better bet for omega 3, as the fish live only in the sea.

Omega 3 is also found naturally in grass and clover. Cattle fed on it have high levels in their meat. Grain, meanwhile, contains very little omega 3 — so factory farmed beef is seriously lacking in this vital acid. Try to buy only pasture-raised beef.

TASTY REASON WHY WE LOVE TOMATOES

THE tomato contains more umami (which, after sweet, sour, salty and bitter, is the fifth taste — a Japanese word that translates as ‘pleasant savoury taste’) than any other fruit. That is a heavy punch and it helps explain why we love them.

The umami molecule is an amino acid called glutamate, which is one of the building blocks of protein.

We have a taste receptor on our tongues that’s on the lookout for glutamate in our food. We are wired to enjoy the taste of protein and to want more.

One of the most umami-rich foods is cured ham made from Spain’s black-footed Iberico pig. The pigs get the umami amino acids from acorns they eat.

During the curing process, more and more glutamate molecules are released in the ham (this is probably true when we cook tomatoes and may explain our love of ketchup).

Other umami-rich foods are beef, chicken, mushrooms, soy and parmesan cheese, or foods that combine them all, such as pizza. The Secrets of Your Food, BBC2, Friday, 9pm.