The kick in alertness from the first cup of morning coffee is just the removal of the fatiguing effects of caffeine withdrawal, scientists say.

The first cup of coffee for java lovers doesn't actually boost alertness, British researchers say following a study of 379 volunteers who were given caffeine or a placebo.

While regular consumption may feel beneficial in terms of alertness, that isn’t actually the case, said study author Peter Rogers of the department of experimental psychology at the University of Bristol.

"That kick in alertness we get from our first coffee or tea in the morning is in fact just the removal of the fatiguing effects of caffeine withdrawal, which occurred from overnight abstinence," Rogers said.

The post-caffeine levels of alertness among frequent consumers were no higher than among non-consumers who received a placebo, the researchers found. The finding suggests caffeine only brings coffee drinkers back up their normal baseline level or alertness but no higher, the researchers said in Wednesday's issue of the journal Neuropsychopharmacology.

It's thought coffee makes people more alert by blocking a receptor in the brain involved in putting people to sleep, said study co-author Prof. David Nutt of Imperial College London.

Coffee culture

Despite the findings, Brian Scott of Toronto said he needs his three cups of coffee in the morning.

"If I don't start with coffee, I don't get fired up on all burners quick enough," Scott said.

In the study, caffeine did slightly increase levels of anxiety in the participants, who had to abstain from the stimulant for 16 hours before the experiment.

The researchers were expecting to find those with a genetic predisposition to the anxiety-provoking effects of caffeine would be deterred from drinking coffee. But some people with the genetic variant actually consumed larger amounts of coffee than those without the genetic variant, Nutt said.

That difference led the researchers to consider how the mild increase in anxiety might be part of the pleasant buzz caused by caffeine — that slight feeling of being on edge or "tense arousal," as Rogers called it.

Withdrawal effects

The pleasant perception of a buzz could also partly explain the appeal of coffee in society, where it brings people together at cafes, Rogers said.

Taste, aroma, the social aspect and the caffeine buzz all contribute to caffeine's popularity, said Sara Spector, owner of Everyday Gourmet, a coffee shop in Toronto's St. Lawrence Market.

But trying to kick the caffeine habit can bring classic withdrawal symptoms such as headaches and tiredness.

During the experiment, neither the participants nor the researchers knew who was consuming caffeine or a placebo.

But when the scientists analyzed the results, they found five participants who withdrew from the study complaining of such symptoms were actually in the placebo group. Instead of showing adverse effects of caffeine, these volunteers were showing adverse effects to caffeine withdrawal, Rogers said.

The slight anxiety effect is only found in consuming the amount of caffeine in coffee, not tea or soft drinks, the researchers noted.

The study was funded by the U.K.'s Biotechnology and Biological Sciences Research Council. Several of the study authors have previously received consulting fees or grants from food manufacturers and pharmaceutical companies.