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The science of chocolate

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 4.4kg (9.7lb) a year in the United States to 8.8kg (19.4lb) a year (in Switzerland), it takes, on average, only a decade to eat a person's worth of the delicious dark brown. [1] 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. Just looking at the photo might be enough to make your brain imagine the smell, taste, touch, and sight of it. Are you drooling... just a little? Is your brain fooled by the possibility of a coming treat?.

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  1. What is chocolate?
  2. Why do people like chocolate so much?
  3. Chocolate on the brain!
  4. Is chocolate good or bad for you? What does the science say?
  5. A brief history of chocolate
  6. Find out more

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 liquor (also referred to as "cocoa liqor" or "cacao liqor") 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 40 per cent or so. White chocolate is made from at least 20 per cent cocoa butter without added cacao liquor. [2]

Two men hold large cacao pods with cacao trees in the background.

Photo: Above: Inspecting cacao pods (left) alongside the trees they come from (right). A typical pod contains something like 25–50 cacao beans. Below: Inside the pod, the beans (brown) are surrounded by a white pulp (also called mucilage). Photos by Peggy Greb (above) courtesy of US Department of Agriculture/Agricultural Research Service and (below) Keith Weller, also courtesy of USDA/ARS.

Cacao beans inside a cacao pod.

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 2007 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 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).

Back in 1996, researchers at the Neurosciences Institute in San Diego, California published a letter to Nature suggesting that 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 speculated (their word) that 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. [3]

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

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.

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. [4]

Chocolate on the brain!

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?

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

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 and Wikimedia Commons.

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.


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Is chocolate good or bad for you? What does the science say?

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; there has been extensive research into how high levels of saturated fats in fatty and sugary foods (such as chocolate) may affect your risk of heart disease, though the position is far from straightforward; and some studies argue there is "no evidence for a link between consumption of chocolate and coronary heart disease".

One key complication is that cocoa 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). It's important to remember the difference between stories like that and evidence-based science.

The antioxidants such as polyphenols, especially flavonols, present in large quantitites in cocoa, cause vasodilation, modulate inflammatory markers and cardiovascular health, and possess a range of protective cardiovascular effects. On the other hand, overconsumption of chocolate can lead to tachyarrhythmias, supraventricular tachycardia, atrial fibrillation, ventricular tachycardia and ventricular fibrillation due to its caffeine content.”

Gammone et al, Impact of chocolate on the cardiovascular health, 2018

The dark side

While we can generalize about "chocolate," we should also bear in mind that the three main kinds of chocolate—dark/plain, milk, and white—are chemically quite different, which means they're likely to affect our bodies and brains in different ways.

Dark chocolate's higher levels of cocoa give it higher levels of a chemical called epicatechin, which has been the subject of numerous recent scientific studies. In 2016, The New York Times reported on an experiment that appeared to show cyclists gained a slight but significant performance benefit by eating small amounts of dark chocolate (compared to control subjects who nibbled white chocolate instead). Two other interesting 2016 studies appeared to show benefical effects of eating dark chocolate for patients recovering from heart failure and enhanced memory formation (though the subjects in the second experiment were snails!). Another paper published that year carried the telling title Chocolate Consumption is Associated with a Lower Risk of Cognitive Decline, and was based on a study of 531 people aged 65 and above carried out over four years. According to the authors, Afonso Moreira and colleagues, the positive effect of chocolate was seen only in those with "average daily consumption of caffeine lower than 75 mg."

How about the claim that chocolate can lower your blood pressure? There's some fascinating recent research into this, including studies of native cultures where low blood pressure seems to correlate with diets high in cocoa. In 2006, McCullough et al reported on a study of the Kuna Indians of Panama, who don't suffer the blood pressure and cardiovascular problems so common in the urbanized west, speculating that their "notably higher intake of flavanol-rich cocoa" could be significant. If chocolate were the cure for high blood pressure, an awful lot of people would be very happy indeed—and shares in chocolate firms would be soaring.

Unfortunately, a 2016 study of 13 systematic reviews "provided strong evidence that dark chocolate did not reduce blood pressure," though it also found strong evidence "cocoa products with around 100 mg epicatechin can reliably increase FMD [flow-mediated vasodilation—dilation of blood vessels to increase flow], and that cocoa flavanol [the nutrients in cocoa such as epicatechin] doses of around 900 mg or above may decrease blood pressure in specific individuals and/or if consumed over longer periods."

A dark chocolate digestive biscuit

Photo: Dark chocolate contains higher levels of cocoa.

So what does it all mean in practice? What you eat, how much, and how often is crucial. The Kuna Indians appear to consume around 1880mg of the critical chemicals each day, while 100g of dark chocolate contains just 170mg. In other words, it looks like you'd need to eat large amounts of dark chocolate (and cocoa) to make a significant difference to blood pressure. Other studies suggest benefits from eating chocolate in smaller quantities. A 2011 review by Buitrago-Lopez et al, published in the British Medical Journal, found "The highest levels of chocolate consumption were associated with a 37% reduction in cardiovascular disease... and a 29% reduction in stroke..." Evidence of reduced stroke risk has been found by other researchers too. A 2017 study of over 80,000 Japanese by Dong et al found "chocolate consumption was associated with a significant lower risk of stroke in women," though there was no significant risk reduction in men (and the researchers couldn't rule out other confounding factors as explanations). In 2020, a systematic review of 27 separate studies of chocolate eating by Jakub Morze and colleagues concluded: "Chocolate consumption is not related to risk for several chronic diseases, but could have a small inverse association with CHD and stroke. Our findings are limited by very low or low credibility of evidence, highlighting important uncertainty for chocolate-disease associations."

All told, then, the science of chocolate is far from clear, and the evidence isn't strong, but this much seems probable: eating moderate amounts of chocolate does you no harm and might even do you some good, while eating too much sugar and fat is generally not a good thing (no surprise there because, as Stephen Fry famously said, that's what "too much" means). 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 and Wikimedia Commons.

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  1.    Euromonitor, 2017, quoted in the [PDF] Lindt Chocolate Annual Report, 2017.
  2.    When It Comes to Chocolate, What Does Cocoa Percentage Actually Mean? by Megan Giller, Chowhound, 11 February 2020 and What Is White Chocolate? by Megan Giller, Chowhound, 14 February 2020.
  3.    Brain cannabinoids in chocolate by E. di Tomaso, M. Beltramo, and D. Piomelli, Nature, 22 August 1996.
  4.    Changes in brain activity related to eating chocolate: from pleasure to aversion by D. Small et al, Brain, September 2001.

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@misc{woodford_2FA, author = "Woodford, Chris", title = "The science of chocolate", publisher = "Explain that Stuff", year = "2008", url = "", urldate = "2023-07-01" }

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