The stimulatory effects of a strong cup of coffee in the morning may be nothing more than an illusion.
People who routinely use caffeinated drinks to kick-start their day derive no actual benefit in terms of increased alertness, compared with those given a decaffinated variety in a recent study.
Instead, they may feel better simply because they are correcting the symptoms of caffeine withdrawal, researchers say.
The study, published online in the International Journal of Neuropsychopharmacology, reports that frequent drinkers of coffee and other caffeinated drinks develop a tolerance to both the stimulatory effects of caffeine and side-effects of increased anxiety.
Tests on 379 individuals who abstained from caffeine for 16 hours before being given either caffeine in pill form or a placebo showed little difference in computer tests designed to gauge their alertness level.
While frequent consumers reported feeling alerted by a cup of coffee that contained about 70-100mg of caffeine, recent studies suggest that this is merely the reversal of the fatiguing effects of acute caffeine withdrawal.
Approximately half of the participants in the latest study said that they drank low or no amounts of caffeine — less than 40mg a day, or the amount contained in a can of cola. The other volunteers reported drinking more than that. All were asked to rate their personal levels of anxiety, alertness and headache before and after being given either the caffeine — as 100mg late morning, and 150mg 90 minutes later — or the placebo pills.
They were also asked to carry out a series of computer tasks to test for their levels of memory, attentiveness and vigilance.
Peter Rogers, who led the study at the University of Bristol, said that caffeine consumption was associated with increased anxiety and raised blood pressure, but did not improve test results.
“Our study shows that we don’t gain an advantage from consuming caffeine — although we feel alerted by it, this is caffeine just bringing us back to normal,” he said. “On the other hand, while caffeine can increase anxiety, tolerance means that for most caffeine consumers this effect is negligible.”
By: David Rose. See the original article at: http://www.timesonline.co.uk/tol/life_and_style/health/article7142601.ece