Sweet with a narcotic centre

When people say they have a craving for chocolate, this may be because it
contains the same active chemical ingredient as is found in marijuana. Mark
Howarth reports

EUROPE first encountered chocolate when Christopher Columbus brought back a
few cocoa beans to a distinctly unimpressed King of Spain. It became
popular in Europe after the return of Cortes from the Aztecs, a
civilisation that used cocoa as currency and considered it the food of the
gods. Here began the world's loveaffair with chocolate. Its immense
popularity today is illustrated by a study suggesting that about 40 per
cent of women and 15 per cent of men in North America experience a craving
for chocolate. Significantly, other sweets are not an effective substitute,
so it is not simply the sugar that causes the craving.

Studies like this make one suspect that there is more to the charm of
chocolate than simply the pleasant experience of eating it the aroma, the
texture, the sweetness, the countless calories! Are there some ingredients
which have a direct effect on one's mood, which subtly influence the
chemistry of the brain?

The answer is yes: a range of studies have opened the door on the
pharmacological firepower that may be at the heart of chocolate's
extraordinary popularity. The most familiar is caffeine, which produces the
feeling of increased wellbeing and alertness familiar to coffee drinkers.
Theobromine, almost identical to caffeine, is also found in chocolate but
has more modest effects. A bar of chocolate is thought to contain a
sufficient dose of caffeine and theobromine to have an impact on a person's
mood.

But chocolate's chemical secrets by no means end here. The pleasure
produced from chocolate may be down to traces of phenylethylamine. This has
a structure a whisker away from amphetamine, also known as "speed", which
mimics many of the effects of adrenaline in the body. Phenylethylamine is a
stimulant even more powerful than amphetamine; in higher doses it produces
euphoria, leaving one buzzing with energy and confidence.

Dr Daniele Piomelli and his team at the Neurosciences Institute in San
Diego have taken the story a major step further: they have succeeded in
isolating cannabinoids from chocolate. Cannabinoids are responsible for the
"high" and enhanced sensitivity to sight and sound experienced after
smoking cannabis/marijuana. As with caffeine and phenylethylamine, most of
their effects work by triggering specific receptors in the brain. What's
more, the active ingredient of marijuana is a pale imitation of the brain's
own trigger for the cannabinoid receptor; one of the cannabinoids in
chocolate, as a certain brand of cola might say, is the real thing.

The cannabinoid receptor is actually designed to bind the neurotransmitter
anandamide. Anandamide, which not inappropriately gets its name from the
Sanskrit word for bliss, is found in chocolate. In addition, chocolate
contains two anandamide mimics. These can't bind to the cannabinoid
receptor themselves, but instead keep occupied the enzyme responsible for
degrading anandamide. Thus these two mimics use an indirect route to
achieve the same end: increasing the anandamide levels in the brain.

While the presence of these powerful compounds is of interest in itself,
nobody would claim that they get a "high" from eating chocolate;
contentment is about as far as it goes. What the cannabinoids may do is to
magnify the sensory pleasures, intensifying appreciation of the taste and
aroma.

The trace of cannabinoids in chocolate could also conceivably produce faint
therapeutic benefits. A lot of effort has gone into developing cannabinoids
for medical use. They have proven abilities in painkilling, relieving
nausea and reducing the high pressure in the eye that causes glaucoma. Also
some cells in the immunesystem have cannabinoid receptors on their
surface, so that anandamide and its mimics are able to combat inflammation.
The challenge for drug designers is to find compounds with the medicinal
properties but without the high that accompanies even quite low doses. Some
might say that blissful relaxation isn't the worst sideeffect in the
world. However, if you are using these cannabinoid drugs every day, other
sideeffects such as dizziness and mild hallucinations would rather
interfere with the rest of your life. Certainly, if someone tells you the
chocolate bar they are wolfing down is "purely for medicinal purposes",
don't be fooled.

The San Diego team's discovery could also provide a solution to one of the
nagging problems of modern life. A commonly observed effect of smoking
marijuana is an increase in appetite. This is probably through the
influence of cannabinoids in the hypothalamus, a part of the brain
controlling hunger. Could the cannabinoids in chocolate have a similar
effect on appetite, leading to the involuntary sensation that one bite is
never enough?

Mark Howarth, 20, is at Oxford University. This article came second in the
younger category of The Daily Telegraph/Nirex young science writer awards,
backed by the British Association for the Advancement of Science.