Swarms of morning commuters
clutch cups of coffee to kick-start the workday. But a new study suggests
caffeine might do more for the brain than boost alertness – it may help memory
Researchers from Johns
Hopkins University looked at caffeine's impact on memory while excluding its
other brain-enhancing factors. The study showed that caffeine enhances certain
memories for up to 24 hours after it's consumed.
"The finding that
caffeine has an effect on this process in humans – the process of making
memories more permanent, less forgettable – was one of the big
novelties," said study author Michael Yassa, an assistant professor of
neurobiology and behaviour at the University of California, Irvine, who conducted
the research while at Johns Hopkins.
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The study, which was funded
by the US National Institutes of Health and the US National Science Foundation,
included more than 100 participants who were "caffeine naive",
meaning they were not big coffee, tea or cola drinkers, Yassa said.
"We picked people who
were getting less than 500 milligrams of caffeine a week," he said.
"Most weren't coffee drinkers. Most had a soda once or twice a week."
Coffee's caffeine content
varies greatly. Most average-size cups contain about 160 milligrams (mg), Yassa
said. But a 16-ounce cup of Starbucks coffee packs 330 mg of caffeine,
according to the Centre for Science in the Public Interest.
A dose of at least 200 mg
of caffeine was needed to enhance memory consolidation, the researchers said.
For the study, which was
published online in the journal Nature Neuroscience, the researchers
asked the participants to look at hundreds of common, everyday images on a
computer screen: shoes, a chair, a rubber duck etc.
"We asked them to tell
us if it was an indoor or an outdoor object, but we didn't really care about
what they said," Yassa said. "We just wanted them to attend to the
object, to get that object into their brains."
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Five minutes after the
participants looked at the images, half were given 200 milligrams of caffeine
and half received a placebo. They returned 24 hours later, after the caffeine
was out of their system, and looked at more images of objects. They were asked
to label the pictures as either old, new or similar to the original images
they'd seen (for example, a picture of a duck they viewed the day before, but
taken from a slightly different angle).
People who had taken the
caffeine were better at distinguishing the similar pictures from the original ones,
and those who had received the placebo were more likely to incorrectly identify
the similar images as the old images, the researchers said.
Yassa said the
caffeine-induced ability to recognise similar, but not identical, images did
not occur when people were given smaller doses of caffeine or when caffeine was
ingested an hour before the picture test.
"On caffeine, the
participants were more likely to identify the similar items correctly as
similar and not old," he said. "In doing so, this demonstrates that
the caffeine enhanced the brain's consolidation process – the process of
making those items more permanent in their memory."
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The study didn't actually
prove that caffeine improves memory, however. One limitation of the study is
that participants knew they were involved in caffeine research, the researchers
In the United States, 80%
of adults consume caffeine every day, according to the US Food and Drug
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