21 February 2017 - DailyMail - Why IS chocolate so impossible to resist? TV doctor reveals the reasons why certain foods can make you addicted

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 IS 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.