U. BUFFALO (US)—For adults, being “addicted” to caffeine is considered perfectly normal, but what effect does chronic caffeine consumption—particularly via soft drinks—have on young people?
And, does consuming caffeinated drinks during adolescence contribute to later use of legal or illicit drugs?
Neurobiologist Jennifer Temple, 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 questions through a four-year study funded by the National Institutes of Health.
Her paper addressing caffeine’s appeal to young soft drink consumers 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 based on gender: The males in the study worked harder and longer on a computer-based exercise to obtain caffeinated drinks.
While 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- to 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 observations led Temple to investigate 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’s hoping to more fully understand the mechanisms that underlie such reinforcement.
The recently published study on the reinforcing value of caffeine involved 26 boys and 23 girls ages 12 to 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.
Participants 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 to avoid 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 says 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 the gender differences could be based on the effect of circulating hormones at the time of the test, although this was not measured, and suggests the possibility that females are less sensitive to caffeine’s effects.
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 drafted reporting the results. A third component of the study that focuses on the effect of caffeine consumption during adolescence on later use of legal or illegal drugs is getting under way.
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