Discovering the Sweet
Discovering the Sweet
Mysteries of Chocolate
By Ellen Kuwana
Neuroscience for Kids Staff Writer
Chocolate History
More than 3000 years ago, the Mayans and Aztecs of the Americas consumed
chocolate. These people drank cacao, or the chocolate bean, which was ground into
hot water, like the hot chocolate we drink today. However, their cacao was rather bitter
and had chilies in it. For those of us who hoard our chocolate candies, it is easy to
understand why the Mayans and Aztecs used cacao beans as currency. Imagine using M&Ms instead of
coins!
How did chocolate spread around the world? In 1502, on his fourth and last voyage
to the New World, Christopher Columbus came upon a canoe that was transporting
agricultural products, including cacao beans. He seized the contents of the canoe and
brought cacao back to Spain. Chocolate did not become popular for many years in
Europe, but decades later, the Spaniards added sugar to the cacao, and the rest, as
they say, is history. Chocolate soon became the preferred drink of the royal courts in Europe. The belief was
that chocolate could cure any illness.
Have you ever seen a cacao bean, (or, as it is more commonly known, a
cocoa bean)? These beans grow on a tree called Cacao theobroma. The
cacao tree is pollinated by insects called midges and by bats and is grown only
within 10-20 degrees latitude of the Equator. These regions include West
Africa, Central America, parts of South America, and the Caribbean Islands.
The beans, which grow in the fruit pods of the tree, are generally harvested
twice a year. Each pod is about the size of a hand and contains 20-50 beans.
The pods turn bright yellow, orange, or red when ripe. The beans are dried, and then the center part is
removed by hand and allowed to ferment. After the beans dry again, they are sold. The chocolate
manufacturer must separate the beans from any debris, remove the hard outer shell, and grind the center part
of the bean.
Chocolate, Chocolate Everywhere
Chocolate candy bars, after-dinner mints, brownies,
truffles, doughnuts, chocolate milk-if it has chocolate in it,
we eat it. Hot, cold, solid, liquid, over ice cream...even
over meat?! Yes, a Mexican sauce called "mole" uses
unsweetened chocolate in a sauce that is served over meat. It's a versatile flavor,
chocolate. Chocolate has been blamed for acne and tooth decay, but research has
found that it is innocent of these evils. That must have made lots of people
worldwide sigh in relief: the chocolate industry sells five billion dollars worth of chocolate each year in the
U.S. alone. The U.S. is only the eighth largest consumer of chocolate. Switzerland, whose citizens eat more
than 21 pounds per person each year, leads the world in chocolate consumption.
An Appetite for Chocolate
Why do we crave chocolate? There are times when nothing else tastes as good as chocolate. There are times
when you want nothing else. Nothing else will do. There's even a name for someone who craves chocolate: a
chocoholic. It's almost an uncontrollable urge.
Some scientists wondered why the average person in the U.S. eats 11 pounds
of chocolate each year. They decided to analyze the contents of chocolate to
find out how those compounds might affect our brains, and thus our moods.
Just as caffeine seems to perk people up, chocolate seems to make us feel
happy.
Chocolate contains approximately 380 known chemicals, so it's no wonder it's difficult to figure out why
chocolate is such a favorite treat. And who's to say that it's only one or two things in chocolate that cause us
to feel happy? Many of the chemicals in chocolate are found in other foods, yet we don't buy heart-shaped
bananas to show that special someone that we care for them. It may be a unique chemical combination that
gives chocolate its edge over vanilla, berry, and caramel. Although chocolate has been said to improve
mood, it contains saturated fat and sugar, too, so don't overindulge-it's not the healthiest food. And keep
chocolate away from Spot! A two-ounce piece of chocolate can be fatal to a dog because it can not digest
one compound in chocolate called theobromine. Chocolate can also make some small children sick for the
same reason.
Chocolate and the Nervous
System
Adam Drewnowski at
the University of
Michigan researched
whether chocolate
triggers the production
of opioids. Opioids are chemicals, such as those found
in opium, that produce a feeling of well-being
(euphoria). Drewnowski found that eating chocolate
causes the brain to produce natural opiates, which dulI
pain and increase a feeling of well-being. If the
receptors in the brain that signal the presence of
opioids were blocked, chocolate bingeing decreased.
It was not shown, however, if this was caused by the
high fat or sugar content of chocolate candy.
Researchers at the Neurosciences Institute in San
Diego, Emmanuelle diTomaso (she's now at Harvard
University) and Daniele Piomelli (he's now at the
University of California, Irvine) looked into the
chemical components of chocolate. They found three
substances in chocolate that "could act as cannabinoid
mimics either directly (by activating cannabinoid
receptors) or indirectly (by increasing anandamide
levels)." What do all these big words mean? A little
background information may help make this more
understandable.
A receptor is a structure on the surface of a cell that
interacts with certain chemicals. Receptors have
different shapes, and thus interact with specific
molecules. diTomaso describes this interaction like
this: "the active compound will lock itself to the protein
and that triggers a reaction inside the cell."
Cannabinoids are substances that act like cannabis,
also known as marijuana. The active chemical in
marijuana is called tetrahydrocannabinol (THC), and
there are receptors in the brain that bind THC. When
THC binds to these receptors, the person feels "high."
Anandamide is a lipid that is normally found in the
brain; it can bind to the same receptors as THC and
thus produce a similar effect to "being high."
Does chocolate affect the brain in the same way
marijuana does? There are chemicals in chocolate that
act like THC, resulting in production of dopamine, a
neurotransmitter. However, there is no THC in
chocolate, so you aren't breaking the law by eating
chocolate. One of the compounds in chocolate is
anandamide, which is already produced in your brain.
If anandamide is already in your brain, then why don't
you feel happy all the time? Well, anandamide is
broken down quickly, so it isn't around long in your
brain to make you smile. But chocolate may extend
the feelings of well being. Piomelli's research indicates
that there are two chemicals in chocolate which inhibit
the natural breakdown of anandamide. This may be a
reason why we like to eat chocolate! And dark
chocolate contains more of these compounds than
milk chocolate.
Eating a bar of chocolate will not make you feel giddy
or "high." This may be because anandamide and the
two compounds that enhance its effect are short-lived
and localized in the brain. THC activates many
receptors throughout the brain, so it has a much larger
effect. Chocolate's effect is limited because
anandamide is not present all over the brain. Scientists
doubt if anandamide and other chemicals in chocolate
have much effect because they are present only in
small amounts. Christian Felder at the National
Institute of Mental Health estimates that a 130-pound
person would have to eat 25 pounds of chocolate at
one time to get any marijuana-like effect. Also, since
these compounds are eaten, it's difficult to determine
how much enters the bloodstream and actually reaches
the brain.
There may also be other explanations for the feelings
caused by chocolate and these may have nothing to do
with cannabinoids, anandamide, or receptors. There
are many other components in chocolate that may play
a role in its popularity. Eating chocolate may be
pleasurable because of a unique interaction among a
few of its components.
Chocolate also contains
phenylethylamine, a
chemical related to
amphetamines. Like
amphetamines, this
chemical causes blood
pressure and
blood-sugar levels to rise, resulting in a feeling of
alertness and contentment. Phenylethylamine has been
called the "love-drug" because it quickens your pulse,
as if you are in love. Caffeine in chocolate may also
cause feelings of alertness and a pounding heart. Other
stimulants in chocolate include theobromine and
methylxanthines. These caffeine-relatives are weaker
than caffeine-you'd have to eat more than 12 Hershey
bars to get as much caffeine as there is in one cup of
coffee. All of these stimulants increase the activity of
neurotransmitters in the brain.
The Synapse
An electrical impulse will trigger the release of
neurotransmitters from vesicles (red dots in the
picture) in the presynaptic terminal. Molecules of
neurotransmitter cross the synaptic cleft and bind
to receptors on the postsynaptic membrane.
Whatever the true reason for chocolate's popularity, scientists will continue to
investigate the sweet mysteries of cacao. In the meantime, grab a bar for yourself and a
box for your Valentine.
Life is sweeter with chocolate.
For references and more information on chocolate, see:
1.Brain Cannabinoids in Chocolate, Nature, August 22, 1996, pp. 677-678 by diTomaso, E., Beltramo,
M., and Piomelli, D.
2.Chocolate-Melting the Myths - An in-depth look at the chemical components of chocolate.
3.Chocolate May Mimic Marijuana - October 1996
4.Chocolate: the Legal 'High', August 21, 1996, Medical Tribune News Service by Mann, D.
5.Chocolate's effect on brain likened to marijuana's - August 21, 1996
6.History and Science of Chocolate
7.Marijuana and Chocolate, AIDS Treatment News 257- October 18, 1996 by James, J.S.
8.Prescription-Strength Chocolate: Food for Thought - October 12, 1996 - A report on the chemistry
behind chocolate and the brain.
9.The Sweet Lure of Chocolate - All about the history of chocolate and research about its effects, plus a
list of references and related links.
10.Second Endogenous Substance Similar to THC Found - September/October 1997
11.Study Disputes Chocolate "High" - December 17, 1998
12.Sweet Science: Chocolate may really be a 'love drug' for the brain - February 10, 1997
13.Sweet Seduction - History of chocolate
14.The Science of Love - Research into why we love chocolate.
15.Trick or Treat from Food Endocannabinoids?, Nature, Vol. 396, December 17, 1998, pp. 636-637,
by DiMarzo, Sepe, DePetrocellis, Berger, Crozier, Fride and Mechoulam - A letter to Nature raising
questions and concerns about the original report of endocannabinoids in chocolate, plus a reply by two
of the authors of the report, Beltramo and Piomelli.
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