Caffeine can help you to lose weight; can increase physical endurance; can avert jet lag; can relieve asthma; can protect smokers' lungs; can assist even dodgy hearts to handle exercise; can help prevent or slow the progression of Parkinson's disease; can aid male fertility; can improve long-term memory; can alleviate migraine; can increase alertness; can have aphrodisiac effects on older people.
All this is true.
On the other hand, caffeine can produce anxiety; can cause peptic ulcers; can increase the risk of hip fracture; can exacerbate circulation problems; can impair short-term memory; can raise the risk of glaucoma; can cause iron deficiency; can aggravate PMS; can cause spontaneous abortions; can reduce male libido; can lead to intoxication in high doses.
All this is also true.
Consider this: a dose of only one gram, equivalent to about six strong cups of coffee, may produce insomnia, restlessness, ringing in the ears, confusion, tremors, irregular heartbeat, fever, photophobia, vomiting, and diarrhoea. The lethal dose for a 14-stone adult is estimated at about 10 to 15 grams. Sudden withdrawal from caffeine drinks often results in headaches, irritability and poor concentration.
Does anyone still doubt that caffeine is a drug? Does anyone believe that it's just coincidence that the world's three most popular drinks - coffee, tea and cola - happen to contain caffeine in significant amounts? It's a drug, all right. It probably won't wreck your life and health, but it's still a drug - the world's most popular, easily surpassing nicotine and alcohol. Furthermore, in the words of the earnest, unsensationalist authors of the The World of Caffeine, it is "the only addictive psychoactive substance that has overcome resistance and disapproval around the world to the extent that it is freely available almost everywhere, unregulated, sold without licence, offered over the counter in tablet and capsule form, and even added to beverages intended for children".
Caffeine has been adored and dissected by artists, musicians and writers, such as Balzac (ratcheting up the doses to the extent of eating dry coffee powder), Rossini ("Coffee is an affair of fifteen or twenty days; just the right amount of time to write an opera"), Samuel Johnson (who drank 40 cups of tea a day), Voltaire, Beethoven and Goethe (who was indirectly responsible for isolating and naming it). It has served as the age-old prop of rebels without a cause, Greenwich Village bohemians, computer freaks and baggy-eyed new fathers. Once prohibited by royal edict and lamented as the bane of "coffee-house widows"; held forth as a cure-all and source of health and creativity; damned as a dangerous, even deadly drug; caffeine has always been a potent conversation starter. From early Stone-Age man getting his caffeine buzz by chewing up every conceivable part of caffeine-bearing plants, to modern researchers agitating over whether it can lead to birth defects and spontaneous abortion, the story of caffeine is a fountain of controversy from start to finish.
As always, there were men who knew exactly where they stood on the matter. "Everybody is using coffee. If possible, this must be prevented. My people must drink beer," declared Frederick the Great - reared on good old beer soup for breakfast - in his 1777 proclamation against coffee. It was a ruinous luxury for common folk, he reasoned, causing money to "flow out" of the country. If beer soup was good enough for the monarch, it was good enough for them.
Some 30 years before, King Gustav III of Sweden had tried something similar and triggered a flourishing bootlegging trade. Determined to prove that coffee was a poison, Gustav ordered a convicted murderer to drink coffee every day until it killed him, as it surely would. As a control, he ordered another murderer to drink tea and appointed two doctors to report on which prisoner was first to die. The upshot was that both doctors died and Gustav was murdered before the tea drinker became the first of the lab rats to succumb - at the age of 83.
Caffeine can also take part of the credit for the emergence of modern civilisation. The theory now is that modern civilisation actually hinged on the conjunction of accurate time-keeping (achieved in the 1660s in England) and caffeine (as an aid to meeting the new demands of invariant scheduling). It stands to reason. The fact that caffeinated drinks contained no alcohol for one thing (at a time when beer for breakfast - not to mention dinner and tea - was standard fare) was surely a huge boon to productivity, not only from the point of view of turning up on time, but for seeing straight.
Nowadays - as we are reasonably sure caffeine in "sensible" amounts will neither kill nor injure us - much of modern life revolves around coffee-houses and caffeine in all its shapes and forms. Coffee-houses have a central role in audience-pulling television shows such as Friends, Frasier and Seinfeld. The world's six top-selling soft drinks have one thing in common - caffeine. (One of them, Mountain Dew, an ordinary soft drink in the US, is considered too supercharged with caffeine to be legally sold in Britain). No self-respecting computer programmer can be seen without a mug of coffee or a trendy high-caffeine soft drink in hand. Manufacturers of caffeine pills - or "alertness" aids - such as Vivarin and NoDoz, operate in a market worth at least $60 million, specifically targeting college students, truck drivers and bodybuilders.
But while the perception is that the US is king of the coffee consumers, Europe is actually way ahead. Finland, believe it or not, tops the lot, followed by Sweden, Denmark, Norway, Belgium, the Netherlands, Germany, Austria, Switzerland and France, with the top four drinking two to three times as much as the US per head.
In 1996, an American magazine conducted a national survey of baby boomers, then turning 50. What did 25 per cent of this "flower-power" generation cite as its drug of choice? LSD, Quaaludes and metamphetamines? Forget it. Caffeine is the new high. "As a drug, caffeine works," say the authors of The World of Coffee. "It wakes you up, improves your cognitive powers, increases your energy output - and yet it is, for all anybody can tell to date, remarkably safe for healthy adults to use in normal quantities."
Coming for a coffee?
The World of Caffeine: The Science and Culture of the World's Most Powerful Drug, by Bennett Alan Weinberg and Bonnie K. Bealer (Routledge, £16.99 in UK)