Despite widespread use among children and adolescents, there has been little research on the effects of caffeine on young people. Now, a new study from researchers at the University at Buffalo School of Public Health and Health Professions, NY, suggests that - after puberty - the bodies of boys and girls respond differently to caffeine.
We know that caffeine increases blood pressure and decreases heart rate across children, teenagers and adults. In the new study - published in the journal Pediatrics - researchers wanted to see how cardiovascular responses to caffeine might differ between girls and boys following puberty, and also whether the menstrual cycle may influence the effects of caffeine on the cardiovascular system.
Previous research by this team - the first to demonstrate gender differences in physiological response to caffeine in adolescents - had found that boys ages 12-17 report feeling "a greater rush" and more energy from caffeine than girls, as well as improved athletic ability.
That study also found that - as caffeine levels increased - diastolic blood pressure increased and heart rate decreased in boys, but not in girls.
New study finds gender differences in caffeine response emerge after puberty
In the new double-blind, placebo-controlled, dose-response study, the researchers examined the heart rate and blood pressure of 54 boys and 47 girls ages 15-17 and 52 prepubertal children ages 8-9 (gender not disclosed).
The study demonstrates that the menstrual cycle contributes to girls' response to caffeine.
After administering either a placebo or two doses of caffeine (1 and 2 mg/kg), the children's heart rates and blood pressure were taken again.
The researchers found that the boys had a greater response to caffeine than the girls did. But gender differences to caffeine response only applied to the postpubertal teenagers. There were no gender differences in the caffeine response of the prepubertal children.
The study also demonstrates that the menstrual cycle does contribute to girls' response to caffeine. "In this study, we were looking exclusively into the physical results of caffeine ingestion," says lead author Jennifer Temple, PhD, associate professor in the Department of Exercise and Nutrition Sciences at the University at Buffalo.
"Phases of the menstrual cycle, marked by changing levels of hormones, are the follicular phase, which begins on the first day of menstruation and ends with ovulation, and the luteal phase, which follows ovulation and is marked by significantly higher levels of progesterone than the previous phase."
During the mid-luteal phase of the menstrual cycle, Dr. Temple found that decreases in heart rate and increases in blood pressure were both greater in the postpubertal girls who had been administered caffeine.
While the study suggests that gender differences in response to caffeine emerge after puberty, the data does not show what causes these differences.
The researchers conclude that further research is needed to determine whether these differences are caused by physiological factors - such as steroid hormones - or psychosocial factors. These psychosocial factors could include differences in patterns of caffeine use, caffeine use by peers or differences in autonomy and control over beverage purchases.
Earlier this year, Medical News Today reported on research from the Centers for Disease Control and Prevention (CDC) that found although overall caffeine intake has not risen among children and adolescents in recent years, children are increasingly consuming caffeine from diverse sources, including coffee and energy drinks.