麻豆传媒

IN THE middle of Portland, Oregon, is Pioneer Courthouse Square, a welcome oasis of open space among the city鈥檚 bustling shops and offices. Business people and spiky-haired teenagers mingle here to wait for a train, eat lunch, or just watch the world go by. But above all they come here to drink. Even by the standards of this coffee-crazy city, the square is awash with caffeine. From 5 am until midnight, some of the city鈥檚 busiest baristas keep the espressos and lattes flowing.

Caffeine is the most widely consumed psychoactive substance on earth, prized by almost every human culture for its ability to perk people up and keep them awake. In North America, around 90 per cent of adults report using caffeine every day.

And when it comes to caffeine delivery systems, our ingenuity knows no bounds. Starbucks, the world鈥檚 largest chain of coffee shops, sells more than two dozen types of coffee and tea. Chocolate is full of the stuff. And throughout the industrialised world, food processing firms are turning some beverages 鈥渄ecaf鈥�, only to 鈥渃affeinate鈥� soft drinks, pick-me-up pills and cold remedies.

But despite its popularity 鈥� or maybe because of it 鈥� many people feel vaguely uneasy about their caffeine intake. There鈥檚 the fact that it鈥檚 addictive. And then there are all the health fears. Odds are that you have heard the rumours. Don鈥檛 drink caffeine, it鈥檒l give you a heart attack. Or a stroke. Or it鈥檒l damage your chromosomes. Or make you fat. Or, or, or.

How worried should we be? True, there are mountains of papers linking caffeine to all manner of health problems. But once you start digging, caffeine鈥檚 critics don鈥檛 have much going for them beyond an almost religious zeal to demonise the stuff. In fact, recent evidence suggests they are dead wrong. Caffeine, it turns out, has a multitude of health benefits. So much so that if most of us weren鈥檛 drinking it already you could argue the case for adding it to the water supply.

Caffeine consumption goes back perhaps 8000 years, but the bad publicity is a much more recent phenomenon. One of the earliest documented health scares came in 1911 when the US government sued the Coca-Cola Company, claiming the caffeine in its drink was 鈥渋njurious to health鈥� (Coca-Cola won).

Caffeine bashing started in earnest in the mid-1970s when several major studies linked it with heart disease and bladder cancer. And that was just the start. 鈥淚鈥檝e probably read 4000 or 5000 caffeine and coffee papers,鈥� says James Coughlin, an independent toxicologist in southern California who鈥檚 been advising the coffee industry for nearly a quarter of a century. 鈥淪omebody has published a paper linking coffee or caffeine with just about every disease known to man.鈥�

Perhaps the most notorious study came in 1980 when Thomas Collins of the US Food and Drug Administration linked caffeine to birth defects in rats. The study sent shock waves through the drinks industry and led the FDA to warn pregnant women to cut down on coffee and tea.

In the study, Collins gave pregnant rats enormous doses of caffeine, equivalent to 200 cups of coffee or tea in one gulp, via tubes inserted down their throats. That method of force-feeding, known as gavage, is a standard laboratory technique for getting foul-tasting substances into lab animals. But it wasn鈥檛 necessary with caffeine, which can simply be added to drinking water. Recognising this, Collins redid his study in 1983 with the caffeine in the rats鈥� water, thereby spreading the dose out across the day in a more realistic fashion. This time there was no increase in birth defects.

Most of the human studies also turned out to have methodological problems. Some indeed showed statistical correlations between caffeine consumption and the risk of getting diseases such as cancer, but they failed to account for smoking 鈥� in part because the link between cigarettes and cancer wasn鈥檛 well understood at the time.

鈥淭here were a lot of spurious results,鈥� Coughlin says, pointing out that while most smokers drink coffee, few people who avoid caffeine smoke. But now that a new generation of studies allows for the effect of smoking and other factors known to be linked to cancer, he says, 鈥渁ny relationship to coffee has fallen away鈥�. Likewise the much-touted link between caffeine and high blood pressure and heart disease. Caffeine does raise blood pressure, but only in people who are not regular users. In 2003, the US National Heart, Lung, and Blood Institute quietly dropped a recommendation that doctors should advise patients with high blood pressure to cut back on caffeine.

Even so, the steady drip, drip, drip of adverse publicity has continued. One recent obsession has been the interplay between caffeine and low-carbohydrate diets, some of which prohibit caffeine on the grounds that it raises insulin levels and thus promotes fat storage. Nutritionists, though, dismiss such simplistic advice. 鈥淭here are numerous processes involved in fat storage,鈥� says Linda Bacon of the University of California, Davis. 鈥淚t may be that caffeine can simultaneously trigger some that are going to encourage weight gain and others that encourage loss.鈥� The literature does not support the assertion that caffeine raises insulin levels. If anything it has the effect of depressing them by decreasing insulin sensitivity.

Another recent flap has to do with caffeine鈥檚 undeniable addictiveness. As every java junkie knows, if you skip your morning brew you鈥檒l be fuzzy-brained and irritable and may also get a headache. No big deal, you might think, and easily remedied. But to some it鈥檚 no laughing matter.

In a study published last October (Psychopharmacology, vol 176, p 1), neuroscientist Roland Griffiths of Johns Hopkins University in Baltimore, Maryland, argued that caffeine withdrawal was serious enough to be added to the next edition of the psychiatrist鈥檚 bible, the Diagnostic and Statistical Manual of Mental Disorders. He reviewed all the literature on caffeine withdrawal and uncovered a dismal litany of symptoms, from headaches, fatigue and depression to vomiting and muscle pain. He also concluded that the benefits of caffeine are an illusion: coffee merely reverses the withdrawal symptoms.

鈥淭he words 鈥榙rug鈥� and 鈥榓ddiction鈥� are powerfully emotive. Nobody robs banks or commits murder for caffeine鈥�

Jack James, a psychologist at the National University of Ireland in Galway and arguably caffeine鈥檚 fiercest critic, would certainly agree. James has long argued that studies showing caffeine鈥檚 positive effects on altertness and mental performance are flawed because the volunteers are habitual caffeine users whose performance on caffeine is being compared with their performance without it. Caffeine doesn鈥檛 make anyone perform better, he argues: it merely restores them to a normal level.

Caffeine supporters, however, believe that this is all a storm in a coffee cup. Just ask anyone who has wrestled with insomnia after an evening brew whether caffeine鈥檚 effect is real or illusory. And sure, caffeine is a habit-forming stimulant, but nobody abuses it. Take too much and you feel jittery and anxious rather than getting high. And nobody ever got mugged by a caffeine junkie. 鈥淎n addictive drug is something you commit a crime for,鈥� says Manfred Kroger, a professor emeritus at Pennsylvania State University and spokesman for the Institute of Food Technologists.

Caffeine researcher Lawrence Armstrong, an exercise physiologist at the University of Connecticut in Storrs, agrees. 鈥淐affeine is a substance of dependence, not a drug of addiction,鈥� he says. 鈥淭he words 鈥榙rug鈥� and 鈥榓ddiction鈥� are powerfully emotive. Nobody robs banks or commits murder for caffeine.鈥�

That鈥檚 not to say that caffeine gets a completely clean bill of health. One real risk, according to Walter Willett, a professor of epidemiology and nutrition at Harvard School of Public Health, is a small elevation in bone fractures among people drinking four or more cups a day. That鈥檚 because caffeine causes some degree of calcium loss, with a possible effect on bone density. But that鈥檚 easily offset by getting enough exercise, calcium and vitamin D, Willett says. In addition, unfiltered coffees such as espresso do appear to have components that increase blood cholesterol. Since filtered brews do not have the same effect, the culprit has to be some as-yet-unidentified component that stays in the filter.

There are also lingering concerns over caffeine in pregnancy. The New York based Center for Science in the Public Interest, a powerful consumer group that has spent years battling nutritionless 鈥渇ood porn鈥�, is largely unconcerned about caffeine for most people. But it does advise pregnant women to switch to decaf. According to Michael Jacobson, the organisation鈥檚 executive director, the literature is unclear but raises some concerns about reduced fertility, underweight babies and (possibly) birth defects. The coffee industry disputes these studies, but Jacobson sees no reason to take a risk. 鈥淔or women who are pregnant, it鈥檚 not a great sacrifice,鈥� he says. For the rest of us, though, he agrees that a couple of cups of coffee is no big deal.

Caffeine supporters, however, aren鈥檛 content with merely countering the critics. Over the past few years they have quietly been building the case that coffee, at least, is positively bursting with healthfulness. Nearly two dozen studies, for example, now show that coffee drinkers have a 25 per cent reduced risk of colorectal cancer, Coughlin says. And the more coffee you drink, the lower the risk.

In addition, several studies have shown reduced risk of liver cancer among coffee drinkers, as well as lower incidence of Parkinson鈥檚 disease and type 2 diabetes. There are even some tentative findings that caffeine may help stave off Alzheimer鈥檚 disease, as well as alcohol-related liver damage. And lest you think the coffee industry or other interested parties funded the studies, these results were by-products of large, multi-purpose cohort studies such as the Nurses鈥� Health Study, administered by Willett under a grant from the US National Institutes of Health.

Willett has also found that coffee reduces the risk of kidney stones. Drinking a lot of any liquid has a similar effect, but coffee is particularly beneficial, probably due to its diuretic effect. Also, he says, coffee lowers the risk of gallstones and, intriguingly, suicide. 鈥淧robably coffee is a mild antidepressant, and for some people it鈥檚 just enough to pull them back from the brink,鈥� says Willett.

Nobody鈥檚 really sure why coffee has such diverse benefits. 鈥淚t鈥檒l be 15 or 20 more years before we nail these things down,鈥� Coughlin says. 鈥淢any people think of coffee as a caffeine delivery vehicle, but in coffee there are probably 2000 other chemicals.鈥�

Coughlin suspects that the anti-cancer effects are due to polyphenols, a class of antioxidants widely touted as the health 鈥済oodies鈥� in red wine, chocolate, tea, and many fruits and vegetables. In lab tests, he says, coffee trumps these other foods in terms of polyphenol content. And a recent study by researchers at the University of Scranton in Pennsylvania found that coffee is the number one source of antioxidants in the US diet.

With such favourable press for coffee, why does caffeine keep on getting it in the neck? Kroger believes that, in part, the problem stems from young researchers trying to make names for themselves. The temptation is to feed massive amounts of a common substance such as caffeine to rats and see what happens. If the rats get sick, it鈥檚 news.

Kroger also believes that the anti-caffeine sentiment is down to health-food advocates鈥� bias against processed foods, a class that includes most caffeinated soft drinks. But he argues that some zealots simply seem to have a puritanical attitude. It鈥檚 as though they believe that if God wanted us to be perky in the morning, we鈥檇 be that way naturally, he says.

When the dust settles, the debate about caffeine turns out mostly to be simple common sense. Too much caffeine will give you the jitters and keep you up at night. It might even give you disconcerting but largely harmless heart palpitations, and you鈥檒l suffer mild withdrawal symptoms if you stop. But all things considered, caffeine is your friend. Worry about something else.