A recent British study says coffee drinking in workplaces is undermining concentration and damaging productivity. Depending on whom you believe, coffee drinking either raises blood pressure, increases the chances of miscarriage and the risk of developing Alzheimer's, arthritis and infertility - or is a powerful protection against the worst effects of bronchial asthma, colon cancer, bladder cancer, hay fever, Parkinson's, heart disease, depression, anxiety, gallstones, dermatitis, chronic angina and hypotension. Besides dehydration, coffee blocks the receptors of adenosine, a chemical in the brain that normally counters the effects of adrenaline - which explains why it does enhance the sense of alertness. A group of Swedish researchers reported in December that women who drank more than four cups of coffee a day in early pregnancy doubled the chances of spontaneous abortion, while caffeine intake is also thought to affect birth weight - though just how it contributes to any of these problems remains mysterious. But the issue reaches far beyond coffee.
Caffeine makes a regular appearance in the ingredients lists of common painkillers.
But since most researchers deny that it has any painkilling function, and argue that one of the key symptoms of caffeine withdrawal is headaches, it doesn't take a particularly paranoid conspiracy theorist to suggest that something vaguely suspicious might be going on. And yet for every study showing a health risk, there is another suggesting benefits. For centuries people have been investigating exactly the same thing. The debate is complicated by the fact that coffee remains, relatively speaking, a drink of the wealthy. Since environmental and dietary factors are likely to mean they contract fewer serious illnesses in any case, epidemiological studies concluding that coffee enhances health are at risk of drawing unsubstantiable conclusions.