Evaluation of caffeinated beverages sold in a national sample of U.S. middle and high schools.

Background: According to recommendations, adolescents should limit caffeine intake to 100 milligrams (mg) per day. High schools (but not middle or elementary schools) participating in the U.S. Department of Agriculture (USDA) National School Lunch Program and School Breakfast Program are allowed to sell beverages with added caffeine to students, but the amount of caffeine is not regulated. The prevalence of caffeinated beverages sold to students, and the amount of caffeine these beverages contain, is unknown.

Objective: To determine: 1) the prevalence and types of caffeinated beverages in U.S. middle and high schools, 2) the amount of caffeine, and 3) whether caffeinated beverage availability and caffeine content varied by school characteristics.

Design: Cross-sectional.

Participants/setting: A national sample of 45 middle and 45 high schools.

Main outcome measures: The amount of caffeine (in mg) per item, determined from manufacturer websites and photographs of ingredient labels for all products sold in schools.

Statistical analyses performed: Descriptive statistics and two sample t-tests were used to examine average caffeine levels. Multivariate analyses examined whether caffeinated beverage availability and caffeine amounts varied by school demographics using multilevel mixed-effects logistic and linear regression models, with random intercepts for school district and schools nested within districts.

Results: Over half (55.6%; n=25) of high schools and 4.4% (n=2) of middle schools sold caffeinated beverages. On average, caffeinated beverages contained 63mg of caffeine. The most common caffeinated beverages were sodas, but coffee (103mg, SD=25) and energy drinks (95mg, SD=14) contained the highest caffeine levels. High schools had a significantly higher odds of selling caffeinated beverages than middle schools (OR=18.30, p<0.01). Beverages were predicted to be 14mg higher in caffeine in high schools than in middle schools (β=13.88, p<0.01).

Conclusions: There is widespread availability of caffeinated beverages in U.S. high schools. The USDA could consider setting caffeine limits for beverages sold in schools to ensure students do not exceed 100mg of caffeine daily.