The Chemistry of Chocolate

13th December 2017

Chemicals, Science

Birds-eye view of cocoa beans and squares of dark chocolate on a table

With Christmas right around the corner, it seems an appropriate time to look into the world’s favourite treat: chocolate. Advent calendars and selection boxes are being arranged in tempting displays in every shop, and now more than ever the population are eyeing up the discounted Lindor boxes glowing ruby red beneath a string of fluorescent lights. So what is it that makes us drool at these displays?

There are many myths surrounding this velvety smooth confection. What is it that makes chocolate so addictive to us? Is it true that chocolate is an aphrodisiac, or that the nation’s favourite luxury is also the nemesis to our beloved canine pals? Join us as ReAgent seek out the answers to these frequently asked questions, and uncover the complex chemistry of chocolate.

Infographic looking into the effects chocolate has on the brain

Is Chocolate an Aphrodisiac?

Studies into the chemistry of love link that rush of butterflies with the ‘molecule of love’: phenylethylamine (PEA). A natural stimulant found in the brain, PEA behaves as a kind of amphetamine. Chocolate is packed full of phenylethylamine, which is why it is thought to have aphrodisiacal properties. This helped propel the notion that chocolate could actually stir arousal in its consumers.

PEA stimulates the production of endorphins in your brain. These are your feel-good hormones that are responsible for your feelings of pleasure. PEA is also known to increase levels of dopamine, another neurotransmitter that is similarly linked with pleasure and arousal. Since chocolate contains levels of PEA, people often believe that eating chocolate helps to stimulate these hormones, resulting in an aphrodisiac effect on the brain.

Well, prepare for this myth to be debunked, because while chocolate can be addictive, its capacity as an aphrodisiac is pretty limited.

When ingested, PEA is broken down by an enzyme called monoamine oxidase (MAO). After being broken down, it will pass into the central nervous system – but only as a very small, unmetabolised amount of PEA. This means that it is unlikely to have any noticeable impact on the brain. Therefore, if you’re chowing down on some Cadbury’s and start to feel a little – ahem – excited, it’s probably the work of the placebo effect.

Chocolate swirl GIF

Is Chocolate Addictive?

Although chocolate doesn’t have aphrodisiac properties, it doesn’t mean that it’s not addictive. Chocolate is a complex mixture that contains up to 800 compounds in every delicious square. Many of these compounds are responsible for its addictiveness, and one of these is tryptophan.

Tryptophan is an essential amino acid found in foods, and is the key ingredient in producing serotonin. Serotonin is a neurotransmitter that helps to regulate our mood. It also promotes feelings of well-being and elation. In fact, a lack of serotonin is often associated with depression. In order for your body to product serotonin, it needs a sufficient supply of tryptophan, which can found in a variety of foods.

Serotonin is biochemically derived from tryptophan, and since the latter is contained in chocolate, it means that eating a bar of this sugary goodness is likely to increase your serotonin levels. If you have ever felt satisfied or comforted while eating chocolate, and found that your mood has been boosted, this is probably why.

Two other substances that constitute many of chocolate’s addictiveness are theobromine and, of course, caffeine. These compounds influence our moods in very positive ways, as well as increasing our state of alertness. There are higher concentrations of theobromine in chocolate than there are caffeine, and so it has a major impact on the addictive properties of chocolate.

Theobromine actually blocks adenosine receptors in the brain, which are inhibitory neurotransmitters. This means that, unlike serotonin, they can actually act as a central nervous system depressant. By blocking these receptors, theobromine further demonstrates how chocolate can be addictive. It not only blocks out the bad stuff, but couples this with enhancing the good stuff. Could theobromine and tryptophan be our new favourite power couple?

Diagram showing electrochemical impulses in the central nervous system

Chocolate Toxicity

While theobromine definitely has its plus-sides, it is also the culprit behind chocolate’s toxicity. Theobromine is actually an alkaloid, meaning that it comes from a class of nitrogenous organic compounds found in plants.

Alkaloids may sound harmless in this regard, but they are far from it. Nearly all alkaloids are poisonous in large quantities. A few examples of plant alkaloids include:

  • Morphine (extracted from the poppy)
  • Cocaine (extracted from coca leaves)
  • Nicotine (extracted from the tobacco plant, belonging to the nightshade family)
  • Strychnine (extracted from the small Hawaiian tree Strychnos nux-vomica)

It is easy to see from this list the addictive and equally toxic properties of most alkaloids. Strychnine, in particular, was widely used as a rat poison in the early twentieth century. If consumed by humans, strychnine can cause fatal muscle spasms by making it impossible to breathe.

In comparison, theobromine seems relatively harmless – and it usually is to humans. This is because the lethal dose for theobromine has been estimated at 1000 milligrams per kilogram of bodyweight. Therefore, an average human weighing approximately 70kg would have to consume 70g of theobromine in order to reach this dose. This means that a human would have to eat a lot of chocolate to reach this dose – approximately 40 bars of Cadbury’s in one sitting could do it, but even then it is questionable.

Toxicity of Chocolate

Is It Bad For Dogs?

While it’s good news for humans, it’s bad news for our canine friends. This is because dogs can be much more easily affected by theobromine due to their smaller size. Whereas the lethal dose for humans is quoted at 1000 milligrams per kilogram of body weight, it drops to 300 milligrams for dogs.

For a small dog of 10kg, this would mean that they would need to consume 3g of theobromine in order to reach that dose. While this is still a lot of chocolate to eat, even for our four-legged companions, it is easy to do when we consider that theobromine in dark chocolate, for example, can be as high as 600 milligrams per 100g.

In this case, the figure required to reach the lethal dose drops significantly, making it much easier for dogs to overdose on the alkaloid. It’s also worth bearing in mind that symptoms such as vomiting and diarrhoea would occur much earlier than it takes to reach this limit.

Chocolate pieces, which can be addictive and promote wellbeing

So it seems there is a dark side to even the sweetest of snacks. Even so, you can continue to enjoy your cocoa binge til your heart’s content – as long as you don’t plan on eating 40 bars at once! 

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