The science of chocolate

Last updated: March 5, 2008.

Here's an amazing factoid 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.

Photo: Making chocolate brownies. Photo by Joshua Word by courtesy of Defence Visual Information Centre.

Why do people like chocolate so much?

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!

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 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 some 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.

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 antioxdiant chemicals called phenolics (found in red wine and tea), which prevent fats from causing a build-up of cholesterol. A recent study of 7841 Harvard graduates that found people who eat chocolate live longer than people who abstain, possibly because of the antioxidants. 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

• 1400-1100BCE: Cacao first cultivated in Central America and Mexico. The Ancient Aztecs gradually discovered they could turn cacao beans into a delicious drink.
• 16th century CE: Explorers from Europe took the beans back to their home countries.
• 18th century: The famous Italian lover Giacomo Casanova (1725-1798) used chocolate as an aphrodisiac.
• 19th century: The chocolate moulding process was invented.
• 1825: Dutchman Coenraad Johannes van Houten (1801-1887) perfected the art of making cocoa butter and powder from cacao beans.
  
• 1875: Swiss chocolate maker Daniel Peter (1836-1919) invented the method of making milk chocolate.
• 1880s: Swiss chocolate maker Rodolphe Lindt perfected a way of making smoother-tasting chocolate using more cocoa butter.