Most people don´t think twice about their caffeine intake. However, it raises blood pressure and thus increases the risk of heart disease. So the widespread use of caffeine is now a cause for concern among scientists and public health authorities. One result of this concern is that you are not allowed to sell energy drinks in France or Denmark. And in other European countries, manufacturers have to label cans with warnings. The United States has no such rule, but many canned energy drinks sold in the USA carry warnings anyway. On the other hand, much of the research suggests that caffeine may have benefits for human health. Studies have shown it helps relieve pain, reduces asthma symptoms, and increases reaction speed. Despite this, a study in Ireland recommended that children and pregnant women, among other groups, shouldn´t drink energy drinks.

But we need coffee – or Diet Coke or Red Bull – to get us out of bed and back to work. For most human existence, the pattern of sleeping and waking has followed sunrise and sunset, explains Charles Czeisler, a neuroscientist at Harvard Medical School. Then, the way we work changed from a schedule built around the sun to an indoor job timed by a clock, and consequently humans had to adapt. Electric light and caffeinated food and drink allowed people to follow a work schedule set by the clock, not by daylight or the natural sleep cycle. Therefore, without caffeine, the 24-hour society of the developed world simply couldn´t exist.

Caffeine helps people try to override the human rhythm that is in all of us, says Czeisler. Nevertheless, he says solemnly, there is a heavy, heavy price to pay for all this extra wakefulness. Without adequate sleep – the conventional eight hours out of each 24 is about right – the human body will not function at its best, physically, mentally, or emotionally, the doctor says.