Dr MAI THI NGUYEN-KIM on the hidden chemistry that rules our lives

Dr MAI THI NGUYEN-KIM on the hidden chemistry that rules our lives

Hidden chemistry that rules our lives and loves: Dr MAI THI NGUYEN-KIM says you can transform your health once you’ve discovered its secrets

As a chemist, sometimes I feel like the mother of an ugly child whose beauty only I can see

‘Chemistry’ is more than just a throwaway word when discussing relationships. In fact, it is key not only to what’s going on around us but also inside our bodies, as a compelling new book explains. 

Written by a well-known German science journalist (and YouTuber, with a science channel, The Secret Life Of Scientists), it demystifies the fascinating science of chemicals lurking in our bodies — and shows you how to use them to your benefit.

As a chemist, sometimes I feel like the mother of an ugly child whose beauty only I can see. Most people see chemistry as evil, poisonous, artificial. But chemistry is everything.

It is a part of everyday life and can affect our health in many ways, from our sleep and stress processes to the way we form relationships and fall in love. Indeed, our bodies are full of chemicals — we call them ‘hormones’ and ‘neurotransmitters’ — and the way they interact with our cells determines our health and behaviour.

Understanding the chemical processes they are involved in can help us take control of our health and improve our lives. 

Get the most out of your ‘wake-up’ hormones 

How well we wake up in the morning is largely determined by two chemicals. We need less of one, melatonin, and more of the other, the stress hormone cortisol.

A chemically perfect morning goes like this: While we snooze, the sun’s first rays shine through our eyelids on to our retina, which is connected to the brain via the optic nerve.

In the brain, the production of the hormone melatonin — the ‘night-time’ hormone that induces sleep — is now inhibited, and while it declines, a pleasant amount of cortisol is released. We then wake of our own accord.

However, artificial darkness (i.e. wearing a sleep mask or closing the curtains) and artificial light can confuse our body clock.

For example, wearing a sleep mask, which blocks out the daylight completely, means our melatonin level won’t drop as quickly in the morning. You will find people who wear these can struggle to wake up, often despite a loud alarm. 

Equally, the ringing of an alarm can disrupt our body clock and trigger a fight-or-flight response in our body, an emergency system designed to save us from danger.

A chemically perfect morning goes like this: While we snooze, the sun’s first rays shine through our eyelids on to our retina, which is connected to the brain via the optic nerve. In the brain, the production of the hormone melatonin — the ‘night-time’ hormone that induces sleep — is now inhibited, and while it declines, a pleasant amount of cortisol is released

In this case, the alarm’s acoustic signal sends a nerve impulse from the brain, which then triggers the release of further stress hormones, adrenaline and adrenocorticotropic hormone (ACTH), which are delivered to various organs.

Finally, more cortisol makes its way to organs as well. The message is, PANIC! This leads to an accelerated pulse, greater blood circulation in the muscles, deeper breathing, dilated pupils, sweating and heightened awareness. All these reactions mean that we are now wide awake. Luckily, we will quickly recover, but it’s still a bit much.

The ideal way to wake up would be the body releasing just enough cortisol to get going, but without the feeling of having to run for your life.

Why butter is a saturated fat 

They are terms that we encounter every day: saturated and unsaturated fats. But what do they actually mean?

All fats are made up of long chains of carbon atoms. Every carbon-to-carbon bond contains energy that our bodies use for metabolic processes.

Fats such as cheese and butter have the most energy of all nutrients. ‘Fantastic!’ our body thinks. Our love for this valuable energy source ensures that we will devour it whenever we can.

Unfortunately, fat is available everywhere these days, and a valuable energy source has become an unhealthy treat. So what is the difference between unsaturated and saturated fat?

Fats such as cheese and butter have the most energy of all nutrients. ‘Fantastic!’ our body thinks. Our love for this valuable energy source ensures that we will devour it whenever we can. Unfortunately, fat is available everywhere these days, and a valuable energy source has become an unhealthy treat

Every carbon atom can form four bonds. Within a fat chain, every carbon atom is bonded to two other carbon atoms, meaning it still has two bonds available.

If you add two hydrogen atoms to each carbon in the chain, you get a saturated fat or fatty acid — i.e. it is ‘saturated’ with hydrogen.

In unsaturated fats, each carbon forms a double bond with another carbon, so there’s only one hydrogen atom attached to every carbon, making it ‘unsaturated’. As the double bonds make unsaturated fatty acids more rigid, their structure is usually ‘kinked’, which alters how it is broken down by the body.

That’s why unsaturated fats tend to produce liquid fats, while saturated fatty acids tend to produce solid fats. (When unsaturated fats aren’t kinked, they are called trans fats — the most dangerous type of fat that we should limit in our diets).

How love causes butterflies in gut 

As well as being a stress hormone, cortisol has another side. You could even call it a love hormone. I can say confidently that my husband, Matthias, and I have the right chemistry. Even after ten years, I still get butterflies in my stomach when I hear his key in the door.

The trigger for that butterfly feeling is anything but romantic, though. It’s another example of a fight-or-flight reaction. It turns out this physical response is part of falling in love.

Love doesn’t just make your heart race; it also increases your cortisol level. Whatever the situation, the fight-or-flight reaction means that the thing we’re about to do is important and needs to take priority. Just like an encounter with a tiger, we have to give it our full attention. So some ‘unimportant’ bodily functions will just have to wait — such as digestion. The blood is diverted away from the stomach, causing that ‘butterfly’ feeling.

So when I see Matthias after a long day, my body says: ‘Drop everything, we can digest later — we need to give this lovely person our full attention!’


When I used to work in a laboratory, there were glass rooms filled with light. A supervisor said: ‘There’s so much daylight, isn’t it great? Daylight stimulates the release of serotonin, the happiness hormone. That’s why our employees are always in a good mood!’

His comment was too simplistic. Serotonin is involved in complex chemical reactions in our bodies and, among its many functions, it influences our mood. In the 1970s, people began to suspect that depression could be caused by low serotonin levels. There was evidence that increasing serotonin in the brain helped combat depression.

For a long time, there was a simple explanation for the mood disorder: it is triggered by an imbalance in the brain and we can combat it with medications to increase serotonin.

However, it is too simplistic to reduce a mental disorder to the absence of a chemical. Just because serotonin helps fight depression doesn’t mean that depression is caused by a lack of serotonin.

Antidepressants that boost serotonin levels do help many people, but the complex link between serotonin and depression remains controversial.


You might be surprised to learn that sweating involves a chemical process in our skin. When we sweat, water molecules — which naturally attract and hold on to one another in their liquid form —are separated by the warmth from our body. This allows the sweat to evaporate, cooling us down.

Looking at it this way, it’s almost stupid to use antiperspirants. Don’t get me wrong, I’m in favour of deodorants — I don’t like being forced off the bus because someone can’t control their trans-3-methyl-2-hexenoic acid (a molecule that causes sweat to smell bad) — but deodorants and antiperspirants are two different things.

Antiperspirants contain aluminium salts, which form tiny plugs that clog our sweat pores to stop us sweating. Aluminium salts have become notorious because high doses are toxic — and have even been linked to breast cancer.

However, the newest data from the European Commission show that the amount of aluminium that enters the body via cosmetics such as antiperspirants is negligible.

So antiperspirants are harmless, but I still find the thought of clogged sweat pores disturbing.

Deodorants contain antibacterial substances that combat the smell. Sweat itself doesn’t smell. When odourless sweat leaves our pores, it’s guzzled up by bacteria that reside in our armpits, which then burp out stinky molecules.

Antibacterial ingredients make life difficult for these bacteria — and paired with a bit of perfume, deodorants can make bus journeys more pleasant.

What we really need is for someone to invent a nose deodorant. It would need to be a spray for our noses that turned horrible stenches into pleasant scents. This is feasible, in theory. For example, room sprays contain cyclodextrins, cage-like molecules that can catch bad smells.

However, this is tricky because cyclodextrins in your nostrils would catch the nice smells, too.


The chemical oxytocin, which plays a role in childbirth (it helps with muscle contractions in the womb), may also underpin the health benefits of a hug. Studies suggest oxytocin boosts trust and facilitates the relationship between mothers and their children, and romantic partners (it is also released during kissing).

But it could have other far-reaching effects, too. German researchers discovered that men under the influence of oxytocin consumed fewer calories from snacks.

The researchers hypothesised that the hormone reduced reward-seeking behaviour through its role in the brain. This could be an interesting way to treat obesity, but more research is needed.

Oxytocin also reduces the ‘noise’ in social situations, allowing us to be more alert to certain stimuli. Researchers are exploring its potential to help people with autism.

Delay morning coffee by an hour 

When we get up, we should ideally wait an hour before drinking our first coffee — our morning boost of cortisol is our body’s own way of waking up. Caffeine also encourages the body to produce cortisol.

As time goes on, your body will acclimatise to that coffee boost by reducing its own morning stress service. So it’s better to wait until your body’s own cortisol boost has levelled out — which takes about an hour — before adding coffee.

Our brain has receptors — think of these like parking spaces on the surface of our cells — on to which hormones or neurotransmitters attach. The caffeine molecule looks confusingly similar to another of the body’s chemicals, adenosine.

Normally, adenosine lets us know when we are tired. The more energy we use, the more adenosine is produced. This blocks our receptors and the more tired we become.

When we consume caffeine, its molecules dock in the receptors. The parking space is now blocked, but the receptor doesn’t ‘see’ any adenosine, it thinks it’s free — and we think we are awake.

For this reason, you should not drink coffee from late afternoon on, as it disrupts our body clock and sleep quality and quantity.

How toothpaste can make teeth stronger

After breakfast, I squeeze the last of my toothpaste onto my toothbrush while my fried egg, bread, coffee and orange juice sit happily in my stomach, waiting for my metabolism (a frenzy of chemical reactions) to work its magic. And there is plenty of chemistry going on in my mouth, too.

We are continually eating sugar in various forms, not (just) because we’re greedy but because our body converts it into energy. Our brain, in particular, runs on sugar, which is why it has us conditioned to love chocolate and gummy bears.

We are not the only ones who love sugar; the bacteria that live on our teeth love it, too.

When we eat sugar or carbohydrates, the bacteria chow down and convert sugar molecules into acid molecules — then leave them on the surface of our teeth, which slowly dissolves the mineral that makes up teeth, known as hydroxyapatite.

Fluoride in toothpaste contains negatively charged ions, which get in when we brush our teeth and force out the harmful acidic ions.

This exchange creates an extremely thin layer of a more solid, more stable mineral called fluorapatite, which cannot really be touched by acids, on the surface of the teeth.

Shark teeth are almost 100 per cent fluorapatite, which makes them particularly solid and explains why shark bites are so painful.

You shouldn’t shower every day 

You might be surprised to learn that daily showering is not only unnecessary but can actually be harmful.

That’s because our skin is densely populated by a variety of microorganisms. This so-called microbiome or skin flora is generally harmless and even useful (for example, it helps maintain the natural pH value of healthy skin).

But when we wash ourselves with soapy water, substances on the skin attach to ‘hydrophilic’ compounds in soap and end up trapped in soap bubbles (known as micelles).

They then get washed away with the water. The same principle applies with washing powder, household cleaners and toothpaste.

Soaps, although very effective at thorough cleaning, can be particularly aggressive. They wash off not only the ‘bad’ bacteria but the beneficial ones, too, and can irritate or dry out the skin.

If the skin becomes too dry, it gets itchy and may even develop tiny cracks — and then it can’t fulfil its protective role because germs and bacteria will get in.

And this is why we should not shower every day.

The breakdown of alcohol in the body is also a chemical process, which in turn affects our health and behaviour. Most of the alcohol is sent to the liver, which breaks it down. A small amount escapes via the lungs — this is what makes your breath smell of alcohol.

These processes are simply the body’s sensible attempt to get rid of the alcohol as quickly as possible. However, it can’t usually keep up with our average drinking speed, and the excess ethanol gets into the brain via the bloodstream. And then the fun really begins.

Alcohol affects the brain in a similar way to sedatives or an anaesthetic — a strange thought when you imagine raucous drinkers dancing on tables. Although drunk people lose their inhibitions, alcohol inhibits communication between our nerve cells. I’m going to introduce you to two more neurotransmitters to help you better understand your drunken self in the future: glutamate and GABA.

When glutamate binds to its receptor in the brain, it activates communication between the nerve cells; when GABA bonds to its receptor in the brain, it inhibits communication between nerves.

The ethanol molecule interacts with the glutamate and GABA receptors. The result? It slows our brains down via two mechanisms.

This explains why it prompts us to shout and dance on tables; the reduced brain activity inhibits social anxiety and general self-control. It also affects our motor skills. 

If our nerve cells are communicating less, then simple tasks like walking in a straight line are harder than usual. We also start to slur our words and react slowly.

Alcohol also increases the release of dopamine, a molecule involved in movement, learning, attention and emotions. It is one of the core neurotransmitters in our reward system: whenever we do something that brings us joy, dopamine is released — and we want more!

Adapted from Chemistry For Breakfast by Mai Thi Nguyen-Kim, published by Greystone Books at £17.99. 

To order a copy for £15.83 go to mailshop.co.uk/books or call 020 3308 9193. Delivery charges may apply. 

Free UK delivery on orders over £20. Offer price valid until May 4, 2021.

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