The upper in the cupper

Coffee: The world loves a cuppa

By Monise Durrani of BBC Science

Caffeine-filled cups of tea and coffee do not really provide the boost to mood and alertness that people think - they just beat withdrawal symptoms.

New research by Dr Peter Rogers, a psychologist from the University of Bristol, shows that caffeinated drinks have a "pick-me-up" effect only because they counter the tiredness, headaches, and slowing of reactions caused by withdrawal from caffeine in the first place.

Dr Rogers and his team found that caffeine gave the biggest lift when people were suffering from overnight caffeine withdrawal symptoms.

They conducted studies in which they gave people fruit juices with caffeine, and compared this with what happened when people were given a drink with no caffeine.

Not surprisingly, when they felt the caffeine-induced lift, people preferred the drink.

Bitter chemicals

"In other words, caffeine influenced the participant's liking for the drink mainly because it relieved the negative effects arising from withdrawal from the caffeine they had consumed the previous day," Dr Rogers told the British Association's Festival of Science in Sheffield.

Dr Rogers believes that this may explain the popularity of caffeine containing drinks.

Worldwide, an estimated 70 milligrams of caffeine per person - the equivalent of one cup of coffee - is drunk every day. Yet tea and coffee contain bitter-tasting chemicals, including caffeine, which people have to acquire a taste for.

He thinks that the feeling of lifted mood as caffeine levels in the body rise once more, becomes associated with the flavour, which is why people come to like the drink.

So, while coffee drinkers may love the drink because of the boost it gives them, it seems that this is not a gain at all, but is merely compensating for the period of time since the last cup.