The science of chocolate
by Chris Woodford. Last updated: August 4, 2021.
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?.
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]
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]
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.
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?
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.
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.
Reference
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, 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). 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."
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 obviously does you
harm (no surprise there because, as Stephen Fry famously said, that's what "too much" means).
Just make sure you get out your toothbrush afterwards!
