BUFFALO, N.Y. -- Caffeine is a stimulant drug, although legal,
and adults use it widely to perk themselves up: Being "addicted" to
caffeine is considered perfectly normal.
But how strong is caffeine's appeal in young people who consume
an abundance of soft drinks? What impact does acute and chronic
caffeine consumption have on their blood pressure, heart rate and
Furthermore, does consuming caffeinated drinks during
adolescence contribute to later use of legal or illicit drugs?
Jennifer L. Temple, PhD, a neurobiologist, assistant professor
of exercise and nutrition sciences at the University at Buffalo and
director of its Nutrition and Health Research Laboratory, is
looking for answers to these three questions through a 4-year,
$800,000 study funded by the National Institutes of Health.
Her paper addressing the first question appears in the December
2009 issue of Behavioural Pharmacology, and is thought to be the
first study to show a gender effect in the appeal of caffeinated
soda in young people.
Given the effects of caffeine in adults, the researchers
expected to see a difference between those who habitually consumed
a lot of soft drinks, and those who consumed few. However, results
showed that the difference was between boys and girls: The boys in
the study worked harder and longer on a computer-based exercise to
obtain caffeinated drinks.
Temple and colleagues now have completed the second part of the
study -- a double-blind, placebo-controlled, dose-response study of
the effects of caffeine on the teenagers' blood pressure, heart
rate and hand tremor. Two papers currently are being written
reporting the results.
The third, and perhaps the most important question in the study,
focusing on the effect of caffeine consumption during adolescence
on later use of legal or illegal drugs, is getting underway.
Temple's primary research interest is a behavior called food
reinforcement. She became intrigued with caffeine consumption in
children after conducting a small study in 8-12-year-olds.
"We had a lot of kids who were drinking not only soda, but
coffee," she relates. "I had 12-year-old girls who said that all
they had that morning was a cup of coffee. I started thinking --
'This can't be good.'"
These findings led her to study how hard a person will work to
obtain a particular food, or in this case, a caffeine drink -- and
how food reinforcement mimics drug addiction. She is trying to
understand the mechanisms that underlie such reinforcement, and if
it can be redirected to a more healthy habit.
The just-published study on the reinforcing value of caffeine
involved 26 boys and 23 girls ages 12-17. The participants, who
were not aware the study was testing caffeine's reinforcement
effects, were placed into groups based on their reported caffeine
consumption, in any form.
Participants underwent a baseline test to determine if they
could taste caffeine in the study drinks (they couldn't), and a
run-through to familiarize them with the computer-based program
they would be using in the experiment.
To give participants experience with the study drinks, they were
sent home with a week's supply of test soda, randomized to be
caffeinated or non-caffeinated, and were instructed to drink a
32-ounce bottle every day, for seven days, and no other soda or
caffeinated products. During the second week, they obtained a
week's supply of the opposite drink.
Participants then returned to a laboratory equipped with two
computers, one on which participants played a computer game to earn
caffeinated drinks and on the other, non-caffeinated drinks,
although the drinks' caffeine status was blinded. The longer they
played, the more difficult the game became.
Temple said the difference in the reinforcing potential of
caffeine between males and females, but not between high and low
consumers, was surprising. "These data are novel and they add to
the small, but growing, body of literature on caffeine use in
children and adolescents."
She speculates these sex differences could be based on the
effect of circulating hormones at the time of the test, although
this was not measured, and the possibility that females are less
sensitive to the effects of caffeine.
Alison M. Bulkley, Laura Briatico and Amber M. Dewey, all former
or current undergraduate students in Temple's lab, also contributed
to the study.
The University at Buffalo is a premier research-intensive
public university, a flagship institution in the State University
of New York system and its largest and most comprehensive campus.
UB's more than 28,000 students pursue their academic interests
through more than 300 undergraduate, graduate and professional
degree programs. Founded in 1846, the University at Buffalo is a
member of the Association of American Universities.