Study debunks caffeine's sobering effects

Drinking a cup of coffee for every cup of spiked eggnog likely won't help you drive home more safety, a study on drunken mice suggests.

Drinking a cup of coffee for every cup of spiked eggnog likely won't help you drive home more safety, a study on drunken mice suggests.

"It debunks the myth that you can sober somebody up with coffee," said study author Thomas Gould, a professor of psychology at Temple University in Philadelphia.

Gould and his colleagues observed mice that had been given ethanol, caffeine, a combination of the two, or neither, as the rodents learned to navigate a maze in the shape of a plus sign.

In one of the arms of the maze, lights went on and sound was emitted from a speaker. Since mice don't like bright, loud areas, they normally learned to avoid that area.

But animals given alcohol didn't learn to avoid the unpleasant environment and didn't remember that it was dangerous, Gould's team reported in the current issue of the journal Behavioural Neuroscience, published by the American Psychological Association.

"One of my colleagues says, 'You know, if you give someone who's drunk a coffee, all you're making is a wide-awake drunk,' and this kind of supports that," Gould told CBC Radio's As It Happens.

The investigators tried to use doses that equate to levels in humans. The lowest dose of caffeine corresponded to about one to 1½ cups of coffee, the highest to about six to eight cups of coffee. The alcohol amounts were designed to produce blood alcohol levels of 0.05 to 0.09 — higher than most legal limits for intoxication.

The mice findings support other research that shows alcohol sedates people and caffeine can reverse some of the sedative effects, but not reaction time. Those studies found when people drank alcohol and then caffeine, their reaction time improved but not to the level of someone who is sober.

The difference in reaction time was nine per cent, which would translate into a large difference in the distance needed to stop if a driver was going at 80 km/h and hit the brakes, Gould noted.

His advice for holiday revellers is to be responsible and plan ahead by establishing a designated driver, or stop drinking early enough to allow blood-alcohol levels to go down before getting behind the wheel.

The important thing is that if someone drinks alcohol and caffeine, they may be more alert, but if they get into an accident and their blood-alcohol level is too high, they will still get into trouble with the law, Gould said.

The results are particularly important for people who have drinks that combine alcohol and caffeine, the researchers said.

In November, the U.S. Food and Drug Administration sent letters to manufacturers of alcoholic drinks that contain caffeine, asking them to prove their products are safe.