Drinking coffee doesn't make you more alert, caffeine study reveals
Coffee addicts are merely staving off the effects of caffeine withdrawal, suggests study. They're no more alert than people who regularly do without.
The millions of us who depend on a shot of coffee to kickstart our day are actually no more alert than people who aren't regular coffee drinkers, say researchers.
A cup of coffee might feel like an essential part of your morning ritual, but a new study suggests it only serves to counteract the effects of caffeine withdrawal that have built up overnight.
"Someone who consumes caffeine regularly when they're at work but not at weekends runs the risk of feeling a bit rubbish by Sunday," said Peter Rogers at the University of Bristol, who led the research. "It's better to stick with it, or keep off it altogether."
Infrequent coffee drinkers who reach for an emergency pick-me-up fare no better. They experience heightened feelings of anxiety, then suffer withdrawal symptoms the next day.
Rogers and his colleagues also examined how genetic differences can influence people's response to caffeine. They took blood samples for genetic testing from 379 volunteers and asked them to abstain from caffeine for 16 hours.
After their spell of cold turkey, they were given either a caffeine pill or a placebo. Later, they took a slightly higher dose of caffeine, or another placebo.
The researchers then used a standard questionnaire called the Mood, Alertness and Physical Sensations Scales (MAPSS) to measure the subjects' emotional state and alertness.
The participants' response to caffeine depended on their normal consumption. Roughly half of the volunteers regularly used medium-to-high levels of caffeine – equivalent to a few mugs of filter coffee per day – while the rest usually had little caffeine or none at all.
Caffeine didn't increase the alertness of any group above the levels of non-users who were given the placebo.
However, caffeine fiends who were given a placebo after abstaining from coffee for 16 hours found themselves feeling less alert and experiencing worse headaches than those who got their usual dose. Four people even had to drop out of the study because their headaches were so bad.
The results were no more encouraging for infrequent users. They reported experiencing more headaches after taking the caffeine pills, but didn't feel any more alert than normal.
The study was published today in the journal Neuropsychopharmacology.
Among people who usually consumed little or none of the drug, a dose of caffeine boosted their anxiety levels. Those who had a variant of a gene called ADORA2A which has previously been linked to panic attacks became particularly anxious after a dose of caffeine.
Medium-to-high level caffeine users didn't become any more anxious after caffeine, implying that regular consumption helps you build up a resistance to its anxiety-inducing effect.
People in this group who were genetically predisposed to anxiety actually drank more coffee than the rest, suggesting that mild feelings of tension might even contribute to their enjoyment of the caffeine buzz.
The research is significant because previous studies into the effects of caffeine have involved far fewer participants. "It's an interesting piece of evidence, and a very ambitious study," said Lorenzo Stafford, a psychologist at the University of Plymouth. "Getting the DNA samples of so many participants is a huge effort."
Jacob Aron, The Guardian
2nd June, 2010