BUFFALO, N.Y.—Scientists at the University of Buffalo are studying caffeine's appeal in young people who consume an abundance of soft drinks and what impact does acute and chronic caffeine consumption have on their blood pressure, heart rate and hand tremor. The researchers also are investigating whether consuming caffeinated drinks during adolescence contribute to later use of legal or illicit drugs.
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 boys in the study worked harder and longer on a computer-based exercise to obtain caffeinated drinks than girls.
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, whose primary research interest is a behavior called food reinforcement, became intrigued with caffeine consumption in children after conducting a small study in 8-12-year-olds. 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.
The 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.
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 no other soda or caffeinated products. During the second week, they obtained a week's supply of the opposite drink. Participants 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 said, adding that these sex differences could be based on the effect of circulating hormones at the time of the test and the possibility that females are less sensitive to the effects of caffeine.