Caffeine's stimulating properties may wane in heavy users

September 11, 2001 in Nutrition Topics in the News

Caffeine's stimulating properties may wane in heavy users

A group of female office workers who were only light users of caffeine showed more mental alertness after being given a dose than those who were heavy users of caffeine, say a team of psychologists from Hofstra University in Hempstead, New York.

In the study the psychologists tracked 48 female office workers who were given either a moderately high dose of caffeine or an inactive placebo on two separate occasions. The women were then asked to type in a page of nonsense prose and a page of regular prose. Some of the women classified themselves as consistently heavy users of caffeine, while others described themselves as light users of caffeine.

The researchers reported that caffeine raised the blood pressure of all the women and increased their typing speed. Most interestingly, the women who rarely used caffeine had the fewest errors when typing the nonsense prose, while the women who frequently used caffeine did not get this increased benefit. This finding only showed up while typing nonsense words, a task that requires heightened mental alertness, rather than typing straightforward prose, which required only automatic and rote attention.

"If you're not a steady user of caffeine, and you're going in for an exam and want to be sharper, drink a couple of Cokes, it's going to help you," the lead research said. "But if you're walking around with a Coke all day, it will probably have less of a benefit."

Short-term caffeine use may not be appropriate for everyone, especially those with high blood pressure or other medical conditions.

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