STORM IN A COFFEE CUP

Chances Are You've Already Had Several Cups Of Tea Or Coffee Today.
Does That Mean You're Addicted To Caffeine? And, Asks Nell Boyce,
Should You Be Worried About It?

The situation was very troubling. Counsellors at the Hazelden
Foundation in Center City, Minnesota, a leading drug treatment clinic,
had learned that some of the residents were smuggling in an addictive
stimulant and sharing it with their friends. This was a clear
violation of the rules, but the clinic's staff concluded that they
would fight no longer, and rescinded the unpopular ban on coffee.

Some of the staff felt relieved. Why withhold a harmless substance
that helped the patients stay off alcohol or crack cocaine? After all,
the founder of Alcoholics Anonymous famously drank vast amounts of
coffee, and almost all AA meetings take place around a coffee pot. But
others were concerned that some patients were drinking so much coffee
they weren't getting enough sleep. And there was a principle at stake.
They felt that the caffeine in coffee was, quite frankly, an addictive
drug.

If that's the case, the whole world is cheerfully addicted. In the US,
almost everyone drinks coffee. In Britain and Australia people drink
coffee and tea. And for Nigerians there's the cola nut to chew on.
People consume vast quantities of caffeine in chocolate and soft
drinks, and even in a pure pill form. But is it truly a drug of abuse
like cocaine or heroin? And if so, should we kick the habit?

These are remarkably tricky questions. Headlines around the world last
year proclaimed that French researchers had proved that caffeine
wasn't really addictive. In July, Astrid Nehlig from the Strasbourg
laboratory of INSERM, the French National Health and Medical Research
Institute, announced that giving rats moderate amounts of caffeine
does not promote activity in a brain region called the nucleus
accumbens, thought to play a role in addiction (ChemTech, vol 29, p
30). Even low doses of cocaine, amphetamines, nicotine and morphine
all activate this part of the brain. "The activation of the shell of
the nucleus accumbens seems to be one of the key mechanisms of
addiction of psychostimulants," Nehlig says.

But what of the other mechanisms and brain structures thought to be
involved in drug addiction, such as the dopamine system? Caffeine
makes us feel alert because it blocks the receptors for a brain
chemical called. adenosine, which normally dampens the activity of
other neurotransmitters. Blocking adenosine boosts brain activity, and
may indirectly boost dopamine levels. Cocaine, alcohol, nicotine and
heroin also raise dopamine levels. "Obviously caffeine shares some
properties with the drugs of abuse," Nehlig admits.

But she rejects the notion that caffeine could be considered an abused
drug. Some scientists think that rises in dopamine levels may be a
general pleasure response, not anything specifically linked to
addiction. The main mechanisms of action of caffeine and the other
drugs are different, Nehlig insists. She points out that with
caffeine, "the extent of tolerance, withdrawal, or reinforcement is
never as dramatic as those observed with the drugs of abuse".

Other researchers don't dismiss these shared properties so lightly. "I
usually steer clear of the word addiction because it's loaded with
additional baggage," says Roland Griffiths, an expert on caffeine at
the Johns Hopkins Medical Institutions in Baltimore, Maryland. But he
points to the behavioural changes that caffeine can bring about. "Over
the last ten years there has been a greater appreciation in the
general public that caffeine is a drug and produces withdrawal, but I
would guess that caffeine users are unaware of the extent to which
their behaviour is controlled by caffeine."

Take, for example, a simple study in which Griffiths gave moderate
caffeine users red or blue capsules containing either a dose of
caffeine or an inert powder. On one day everybody got a caffeine pill
of one colour, and on the next day they got an inert pill that was the
other colour. The following day they got to choose whichever colour
they preferred, and 80 per cent of the time they chose the caffeine
pill, regardless of whether this was red or blue. He told the
participants that they were testing the effects of compounds found in
common foods, so they had no idea what they were taking.

People clearly seek out caffeine, and when they can't get it they're
not happy. This fact should be obvious to anyone who has ever tried to
function in the morning without their usual cuppa, but until recently
most researchers assumed that caffeine withdrawal was mild and
transient. "There seemed to be an almost flat-out denial on the part
of many that this is of any relevance and/or importance," says
Griffiths. "Caffeine withdrawal occurs at much lower doses than we had
previously recognised."

Withdrawal can occur in people who have as little as 100 milligrams of
caffeine a day, about the amount in two cups of tea or one cup of
instant coffee. Symptoms include headache, fatigue, difficulty
concentrating and drowsiness. The ill effects peak after a day or two
without caffeine, and can continue for more than a week. Surprisingly,
Griffiths says, withdrawal can be suppressed by rather low levels of
caffeine. If you usually imbibe three cups of coffee a day, or around
300 milligrams of caffeine, you can alleviate withdrawal symptoms with
as little as 25 milligrams. "There may be lots of people who are
dependent who think they are immune to withdrawal," notes Griffiths.
Someone who skips their morning coffee and then has a cola with lunch
won't suffer as badly.

Slow reactions

Some researchers worry that children are especially vulnerable to
withdrawal, as they often don't have steady access to ca feine. Gail
Bernstein at the University of Minnesota in Minneapolis studied 30
children at times when they were drinking caffeine regularly and
during withdrawal periods. She showed that they had slower reactions
in tests that required them o watch a computer screen and click a
mouse in response to certain images during periods of withdrawal
Journal of the American Academy of Child & Adolescent Psychiatry, vol
37, p 858). "It's maybe hard to say what you can transfer from the lab
to the real world," she admits, but thinks the issue deserves more
study, given the aggressive promotion of soft drinks to children.

Although adults tend to drink the same amount of caffeine from day to
day, Griffiths says there is no convincing evidence that people can
monitor and regulate their caffeine intake. But in one study he did
show that if people are given coffee containing different doses of
caffeine, they tend to drink more when the dose is low. He notes that
"if you put someone in withdrawal, they're going to head towards
caffeinated foods".

Researchers have also found that as people get used to drinking
coffee, they acquire tolerance to its effects. In one study, people
given 400 milligrams of caffeine a day initially experienced sleep
problems. But after a week, their total sleep time, and the number of
times they awoke, returned to normal. In another study, people got
either caffeine or a placebo for 18 days. The two groups did not
differ significantly in ratings of mood, until they were given a
300-milligram dose of caffeine: this made people in the placebo group
nervous and jittery, but had no such effect on the group that was
chronically exposed to caffeine.

At a biochemical level, caffeine increases levels of catecholamines,
the neurotransmitters involved in the fight-or-flight response. So
your body reacts in the way it would if you were facing down a lion:
your pupils dilate, your breathing tubes open up, and your muscles get
ready for action. Individuals differ in their reaction to caffeine.
Part of this is down to genes, but there are other influences too. The
half-life of caffeine is normally four to six hours, but this doubles
in women taking oral contraceptives and is halved in smokers. Smokers
are more likely than non-smokers to be coffee drinkers, and ex-smokers
consume more coffee than nonsmokers but less than smokers. If someone
quits smoking but keeps drinking their usual amount of coffee or tea,
their caffeine levels can suddenly rise to levels that make most
people feel jittery, complicating efforts to stay off the cigarettes.

We all know why people should quit smoking. But does continually
drinking coffee or tea have any health risks that might make it worth
giving up? Large quantities of caffeine are deadly: tea or coffee
could kill you, if you managed to drink between 50 and 100 cups in one
go. Your liver treats caffeine like any other poison, and plants
produce it to keep pests at bay. Yet evidence for coffee's
contribution to common diseases remains far from clear. "You'll find
that most people go into hyperbole on one side or the other," says
Griffiths.

Health worries have been around since at least 1674, when women in
London claimed it made their men impotent, according to Mark
Pendergrast's 500-page opus on coffee, Uncommon Grounds. The most
recent coffee concerns began in the 1970s, when epidemiologists linked
coffee consumption to heart disease, pancreatic cancer and
reproductive problems. More than twenty years later, these links
remain controversial, and scientists have yet to confirm any of them.
Several large epidemiological studies have failed to find any
association between coffee consumption and heart disease.

James Lane of Duke University Medical Center in Durham, North
Carolina, is convinced that there are risks, however. Caffeine raises
blood pressure, and so could contribute to heart disease later in
life, he says. Over the past ten years Lane has shown that the
caffeine in four or five cups of coffee can raise blood pressure by
about five points and increase production of stress hormones such as
cortisol and catecholamines. "People in high-stress jobs become
dependent on caffeine. But the caffeine is making the stress in their
life worse," says Lane.

Lane believes that we haven't picked up this increase in risk because
people don't report their caffeine intake accurately. They just don't
realise how much they take in, he says, especially when one cup
doesn't always equal another. A large coffee from Starbucks, for
example, can contain a whopping half-gram of caffeine, while a small
cup of instant may contain less than 100 milligrams (see "What's your
dose?", below). And consumption isn't necessarily consistent over the
years.

There are further complications, too. Coffee and tea are a soup of
many chemicals, not just a vehicle for caffeine, says Peter Martin, of
Vanderbilt University's new Institute for Coffee Studies in Nashville,
Tennessee. Studies by Lane and others that use pure caffeine miss the
point, Martin says, because substances such as chlorogenic acids are
more abundant in coffee than caffeine. "There may be pharmacological
interactions that counteract the effects of caffeine," Martin says. He
notes that chlorogenic acids have been shown to affect opiate
receptors in the same way as naltrexone, a medication that blocks the
"high" feeling that makes people want to use narcotics and alcohol.

Even the way coffee is prepared can create different compounds with
effects of their own. In 1996, Dutch investigators reported that
unfiltered coffee made in a cafetiere or "French press" raised levels
of harmful cholesterol by 9 to 14 per cent, while the same amounts of
filtered coffee had no effect. The researchers attributed the effect
to cafestol and kahweol, alcohols found in coffee oils (British
Medical Journal, vol 313, p 8). It's perhaps not surprising that there
is no clear picture of the effects of caffeine on health.

Mark Klebanoff of the National Institute of Child Health and Human
Development near Washington DC decided that rather than relying on his
volunteers to report their own caffeine intake, he would look for a
metabolite of caffeine called paraxanthine in blood samples to test
whether caffeine has any effect on rates of miscarriage. "It's not
perfect, but at least it's looking at the issues in another way," says
Klebanoff. The study found an increased risk of miscarriage only in
women with the very highest levels of paraxanthine, corresponding to
more than five cups of coffee a day. Klebanoff views the results as
"at least reasonably reassuring for women". Many pregnant women say
they quit drinking coffee anyway, because they lose the taste for it.

Brenda Eskenazi of the University of California School of Public
Health in Berkeley thinks that women should minimise their caffeine
intake during pregnancy just to be safe. She notes that caffeine can
cross the placenta, is present in breast milk, and has a longer
half-life in a pregnant woman's body (11 hours compared to 6). Studies
have shown that low doses of caffeine can change a fetal heart rate
even when the caffeine has no apparent effect on the mother.

The debate over health effects is likely to continue for as long as
people keep drinking coffee and tea. But Klebanoff doesn't think we
should worry too much about caffeine. "It didn't take us long to
figure out that cigarettes were bad for you," he points out. "If there
was something terrible that it does to us, we would have found it by
now." But caffeine consumption is so widespread that even small risks
for individuals could add up to major problems for society as a whole.
"It's such a popular drug," says Lane. "I think we really need to have
more people investigating it, just for peace of mind."

Most people who come to work in Griffiths's lab decide that they want
to give up caffeine, once they see the evidence of their dependence
and how it influences their daily life. If you want to quit, Griffiths
suggests that you first spend a week keeping a careful log of your
intake. Then taper off slowly, rather than quitting cold turkey, to
minimise withdrawal symptoms. But be warned: caffeine has a powerful
allure. "Without exception, people in time have decided to go back,"
says Griffiths, who admits to drinking an occasional caffeinated
beverage. "If I have a message it's that people should know that
caffeine is a drug and that they should treat it with respect."
~~~~~~~~~~~~~~~~~~~~~~
Further reading: Uncommon Grounds: The History of Coffee and How It
Transformed Our
World by Mark Pendergrast (Basic Books, 1999) "Caffeine Dependence
Syndrome" by Eric C. Strain and others, The Journal of the American Medical
Association, vol 272, p 1043 (1994)