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The science of chocolate

by Chris Woodford. Last updated: January 10, 2014.

Here's an amazing little fact for you: every ten years or so, a typical adult eats their own body weight in chocolate! That's absolutely true. With typical choc consumption ranging from about 5kg (11lb) a year in the United States to 9.5 kg (21lb) a year (in Switzerland), it takes only a decade to eat a person's worth of the delicious dark brown. But just what is it that makes us eat so much chocolate? Why is it delicious to the point of being addictive? Scientists have come up with various theories...

Photo: Yum chocolate. Now if you'll just excuse me, I have an appointment with my electric toothbrush.

What is chocolate?

Chocolate is a food derived from the beans of the tropical cacao tree (Theobroma cacao), much of it grown in western Africa where high temperatures and rainfall provide perfect growing conditions. The chocolate you eat is produced from cacao beans in a multi-stage process. After harvesting, the beans are allowed to ferment, then dried, cleaned, and ground to produce a paste. This is then pressurized to form two ingredients known as chocolate (cocoa) liquor and cocoa butter. Different types of what we call chocolate are made by blending the liquor and the butter in varying proportions. The finest dark (plain) chocolate is made with at least 70 per cent cacao liquor and butter, while milk chocolate is made with only 50 per cent. White chocolate is make from cocoa butter without added cocoa liquor.

Why do people like chocolate so much?

"For a dose of phenylethylamine, he prescribed himself a dozen ounces of chocolate. Recently it had helped lift the cloak of winter evenings."

The Echo Maker, Richard Powers

According to a recent study by psychologist David Lewis, letting chocolate dissolve slowly in your mouth produces as big an increase in brain activity and heart rate as a passionate kiss—but the effects of the chocolate last four times longer! Trust science to tell us things we already know!

Chocolate bar showing ruled lines that increase stress and make it easier to break into pieces.

Actually, scientists have been trying to understand the chemistry of chocolate for years. Although there are several hundred different chemicals in your typical slab, a handful of them seem to be more important than others in making chocolate taste so good. Among the most important are stimulants including theobromine, phenylethylamine, and caffeine (in very small amounts). Researchers at the Neurosciences Institute in San Diego, California say chocolate also contains a feel-good chemical called anandamide, which is found naturally in the brain, and is similar to another one called anandamide THC (tetrahydrocannabinol) found in marijuana. Normally anandamide is broken down quite quickly after it is produced, but the San Diego chemists think the anandamide in chocolate makes the natural anandamide in our brain persist for longer—in other words, giving us a longer-lasting "chocolate high." So while chocolate does not contain the same active chemicals as marijuana, there is some similarity in the effect that both substances have on our brains.

Other scientists have used brain scanners to study how brain activity changes when we eat chocolate. Scanners like this are based on the neurospsychological idea that different parts of our brains have sometimes quite specialized functions—even to the extent that some bits work almost like discrete modules. In 2001, as part of their research into eating disorders, Dana Small and her colleagues asked their experimental subjects to eat chocolate until well beyond the feeling of satisfaction. They noted one set of brain structures were active when people were still finding the chocolate pleasant (specifically, the subcallosal region, caudomedial orbitofrontal cortex (OFC), insula/operculum, striatum and midbrain), while an entirely different set became active (parahippocampal gyrus, caudolateral OFC and prefrontal regions) once people had eaten too much. Too much chocolate is not necessarily bad for you, but your brain certainly might see it that way.

Photo: Chocolate break? Chocolate and candy bars are usually molded so they have marks along their length where you're supposed to break them. But how exactly how does this help? When you apply a force to either end, it sets up stress throughout the bar. The stress runs in parallel lines down the whole length of the bar but the molded ridges mean the stress is concentrated there—just as it would concentrate around an accidental crack. The bar breaks naturally at these points just as a block of wood would break if it were cracked in the same place and flexed the same way.

Chocolate on the brain!

A patient undergoes an fMRI scan while a technician watches the scan forming on a computer monitor.

Maybe you love chocolate and I hate it— or I love it and you hate it. Either way, what makes us so different? When the two of us peel the wrapper off a chocolate bar and slide it in our mouths, do different thoughts run through our minds? Indeed, do our minds behave in completely different ways?

Those are the sorts of questions neuroscientists have been trying to answer with fMRI (functional magnetic resonance imaging) brain scanning. It sounds complex, but the idea is simple: load your victim inside the scanner (with or without chocolate in their mouth), scan their brain, and see which brain bits "light up" in response. Can you see a difference between the brain scans of choc lovers and others?

Oxford University psychologists Edmund Rolls and Ciara McCabe tried this in 2007 in an attempt to understand whether people (like me) who crave chocolate show a different brain response to those who don't. They found significant differences between choc-o-holics and non-choc-o-holics in three key areas of the brain known as the orbitofrontal cortex, the ventral striatum and the pregenual cingulate cortex. From previous research, these areas of the brain are known to be involved in other forms of addictive behavior, such as drug-taking, drinking, and gambling. Interestingly, Rolls and McCabe found differences using either pictures of chocolate or chocolate placed in a subject's mouth—so even looking at chocolate is enough to set off your craving. Not that choc-o-holics need scientists to tell them that, but it's something worth remembering: if you're dieting, and trying to cut out the choc, avoiding the sight of the forbidden food may be just as important as avoiding the nibbling of it.

Photo: A typical MRI scan. You can see the patient disappearing into the scanner (the white tunnel in the background) while a medical technician views the results on a computer screen in the foreground. Photo by Seth Rossman courtesy of US Navy.

Reference

So is chocolate good or bad for you?

Everyone's heard dentists say "Don't eat too much chocolate!", but the chocolate itself is harmless to your teeth: the problem comes from the sugar in chocolate products. It makes a sticky substance called plaque, which feeds the bacteria that cause tooth decay and gum disease. Other health effects of eating chocolate remain unclear. Some studies suggest moderate amounts of chocolate can help to lower blood pressure, while others point to the high levels of saturated fats in chocolate products, which increase blood cholesterol and raise your risk of heart disease. To complicate things further, chocolate also contains high levels of antioxidant chemicals called phenolics (found in red wine and tea), which prevent fats from causing a build-up of cholesterol. A 1998 study of 7841 Harvard graduates by Dr I-Min Lee that found people who eat chocolate live longer than people who abstain, possibly because of the antioxidants: "... we estimated that (after adjustment for age and cigarette smoking) candy consumers enjoyed, on average, 0.92 (0.04 to 1.80) added years of life, up to age 95, compared with non-consumers." There's also anecdotal evidence that chocoholics live longer. Jeanne Calment (1875-1997) ate about a kilogram (two pounds) of chocolate per week and lived to the age of 122 (but she also rode a bike, smoked, and put olive oil on her skin, so no-one knows exactly what her secret was).

All told, then, the science of chocolate is far from clear, but this much seems probable: eating moderate amounts of chocolate does you no harm and might even do you some good. Just make sure you get out your toothbrush afterwards!

A brief history of chocolate

A cook makes chocolate deserts at a recreational cookery school.

Photo: Now you know: there are good scientific reasons for making chocolate deserts! Photo by Kiona Miller courtesy of US Navy.

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Text copyright © Chris Woodford 2008, 2011. All rights reserved. Full copyright notice and terms of use.

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Woodford, Chris. (2008) The science of chocolate. Retrieved from http://www.explainthatstuff.com/scienceofchocolate.html. [Accessed (Insert date here)]

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