Everyone knows that caffeine is useful on occasion if we need to stay alert, especially when we’re sleepy. Is there any college graduate who hasn’t had a caffeine-fueled all-night study session before an exam? I certainly remember several nights in which I drank coffee to the point of inability to blink, much less sleep.
But for those who drink a lot of coffee daily, how much of a boost in alertness are they getting? A study in this issue of Neuropsychopharmacology offers an interesting insight.
Over 300 subjects were randomized to receive either caffeine tablets or placebo tablets. They all had to abstain from caffeine for 16 hours before the experiment. The caffeine group then received a 100 mg caffeine tablet and 90 minutes later a 150 mg caffeine tablet. (These doses are roughly the amount in a cup of coffee. See the Mayo Clinic link below for an interesting review of the amounts of caffeine in different beverages.) The placebo group received a placebo tablet and 90 minutes later a second placebo tablet. The subjects were asked about headache and alertness before and after each dose.
The responses varied depending on the subjects’ usual caffeine use. Those who normally were moderate to heavy users of caffeine reported an increase in headache and a decrease in alertness after placebo but not after caffeine. So after caffeine they were feeling normal and without it they were having withdrawal symptoms – headache and sleepiness. Surprisingly, even those who normally use little or no caffeine didn’t report any more alertness after caffeine than after placebo. But at least they weren’t having withdrawal symptoms with placebo.
So it sounds like heavy coffee drinkers aren’t getting a boost from their coffee. They’re just avoiding withdrawal. They should probably slowly decrease their use of caffeine to more reasonable ammounts.
And those of us who drink little coffee are probably experiencing a boost from psychological conditioning as much as from caffeine. We expect the hot fluid that we know so well to make us more alert, so it does. If someone slipped us decaf without our knowledge it would likely work almost as well.
To celebrate this new-found wisdom, I’m going to go home and drink Diet Coke until I have palpitations.
BBC News article: ‘People become immune to coffee boost’, experts believe
Mayo Clinic article: Caffeine content for coffee, tea, soda and more
Neuropsychopharmacology article abstract: Association of the Anxiogenic and Alerting Effects of Caffeine with ADORA2A and ADORA1 Polymorphisms and Habitual Level of Caffeine Consumption
I’m happy to report that US Airways Magazine has reprinted my post Erroneous Evidence About Enough Exercise in their current issue. So if you’re flying US Airways this month please grab a copy and brag to your friends that you were reading my posts years before I was cool.
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