That morning cuppa may not actually help get you going

University of Bristol researchers say the caffeine eases withdrawal symptoms which build up overnight, but does not make people more alert than normal.

The work, presented to the British Nutrition Foundation conference, showed only people who have avoided coffee for a while will get a buzz from caffeine.

But the British Coffee Association said regular drinkers did feel more alert.

That alertness you feel is you getting back to normal

Professor Peter Rogers, Bristol University

Those who swear by their morning caffeine fix say it wakes them up, and if they missed out they would feel sluggish and unable to get on with their day.

But the Bristol researchers, who carried out a review of previous studies into the effects of caffeine, say all the drink does is counteract the mild caffeine withdrawal symptoms people are experiencing because they have gone without the stimulant overnight.

And those who drink a caffeinated drink first thing are no more alert than those who never consume one.

'Back to normal'

Professor Peter Rogers, a biological psychologist who led the research, told the BBC: "We do feel a boost from caffeine in the morning, but that's probably due to a reversal of the withdrawal symptoms.

"That alertness you feel is you getting back to normal, rather than to an above normal level.

"That morning boost is what people think is useful about caffeine, but if that doesn't happen, maybe it's not that useful after all."

Professor Rogers said caffeine did have some benefits, such as preventing cognitive decline in the elderly.

But he said it was usually be best to opt for decaffeinated drinks - although the odd coffee could help.

"If you're not a regular consumer, you might get something out of one or two drinks. But once you're a regular consumer, you're in a cycle of withdrawal reversal."

Zoe Wheeldon, of the British Coffee Association, said the research was interesting.

But she added: "There are two sides to the debate and a wealth of scientific evidence suggests that moderate coffee consumption of four to five cups per day is perfectly safe for the general population and does have a beneficial effect on alertness and performance even in regular coffee drinkers."