Caffeine study finds different effects on boys and girls after puberty: study

With the rising popularity of energy drinks, caffeine intake by children and adolescents has increased substantially as some drinks are being marketed for  children as young as four, www.science20.com reported.

Unlike nicotine, caffeine had slipped under the cultural radar as a harmless drug, even for kids, but new study reveals that after puberty, boys and girls experienced different heart rate and blood pressure changes after consuming caffeine. Girls also experienced some differences in caffeine effect during their menstrual cycles.

The study found an interaction between gender and caffeine dose, with boys having a greater response to caffeine than girls, as well as interactions between pubertal phase, gender and caffeine dose, with gender differences present in post-pubertal, but not in pre-pubertal, participants.

"It examined heart rate and blood pressure before and after administration of placebo and two doses of caffeine (1 and 2 mg/kg) in pre-pubertal (8- to 9-year-old; n = 52) and post-pubertal (15- to 17-year-old; n = 49) boys (n = 54) and girls (n = 47). "

Previous studies have  found that caffeine increased blood pressure and decreased heart rate in children, teens and adults, including pre-adolescent boys and girls.

The purpose was to learn whether gender differences in cardiovascular responses to caffeine emerged after puberty and if those responses differed across phases of the menstrual cycle.

According to Jennifer Temple, PhD, associate professor in the Department of Exercise and Nutrition Sciences, University at Buffalo, the researchers found an interaction between gender and caffeine dose, with boys having a greater response to caffeine than girls, as well as interactions between pubertal phase, gender and caffeine dose, with gender differences present in post-pubertal, but not in pre-pubertal, participants.

The study involved 96 children, including pre-pubertal and post-pubertal children.

"Finally," Temple said, "we found differences in responses to caffeine across the menstrual cycle in post-pubertal girls, with decreases in heart rate that were greater in the mid-luteal phase and blood pressure increases that were greater in the mid-follicular phase of the menstrual cycle."

(Read more: Caffeine affects boys and girls differently after puberty, study finds)