Written by: Catharine Paddock, PhD
A UK-led study suggests the notion that caffeine makes us more alert is more imagined than real and that frequent coffee drinkers develop a tolerance to both its stimulatory and anxiety-producing effects.
You can read about the study led by researchers at Bristol University in the 2 June advanced online issue of the journal Neuropsychopharmacology.
While frequent coffee drinkers may feel alerted by coffee, the study suggests this is just a sign of reversing the fatigue effect of caffeine withdrawal, and given that caffeine also increases anxiety and blood pressure, there is no net advantage.
Co-lead author Dr Peter Rogers, of the Department of Experimental Psychology at Bristol told the media that:
“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.”
“On the other hand, while caffeine can increase anxiety, tolerance means that for most caffeine consumers this effect is negligible,” he added.
For the study, the researchers recruited 379 people of whom about half were classed as non or low coffee consumers, while the other half were classed as medium to high coffee consumers (a few large cups of filter coffee a day).
But they found little variance among their levels of alertness when they consumed either caffeine or a placebo after not consuming it for 16 hours.
After giving blood samples for genetic testing, all the participants were asked to abstain from caffeine for 16 hours and then took a dose of 100 mg of caffeine or a placebo. 90 minutes later they then took another 150 mg dose of caffeine or placebo.
The participants rated their own levels of anxiety, alertness and headache before and after consuming either the caffeine or the placebo, and they also completed a series of computer tasks to test memory, attentiveness and vigilance. One of the tests they completed was the Mood, Alertness and Physical Sensations Scales (MAPSS).
The results showed that the medium/high coffee consumers who had the placebo reported a decrease in alertness and an increase in headache.
Neither of these symptoms were reported by medium/high coffee consumers who had the caffeine, yet their post-caffeine levels of alertness were no higher than the non/low consumers who had a placebo.
The researchers said this suggests that the caffeine just brought the medium/high consumers “back to normal”.
Rogers and colleagues also found that genetic predisposition to anxiety did not stop coffee drinking: on the contrary, participants with such a genetic predisposition tended to consume slightly more than those without the genetic variant.
They said perhaps a slight increase in anxiety is part of the pleasurable buzz that caffeine gives.
They concluded that:
“With frequent consumption, substantial tolerance develops to the anxiogenic effect of caffeine, even in genetically susceptible individuals, but no net benefit for alertness is gained, as caffeine abstinence reduces alertness and consumption merely returns it to baseline.”
Source: Medical News Today