Metabolic and Genetic Impacts of Energy Drinks in Youth

This study will recruit male and female adolescents (aged 13-19y). Eligible participants will be booked for an initial visit where parental consent (where necessary ie. under 18 years of age) will be obtained; individuals will then be screened for overall health status. Self-report questionnaires will be administered to participants and will include information on stage of physical development (Tanner Staging), medical history, ethnicity, caffeine use (including CCEDs), gaming, physical activity and smoking status (iPad based). In the second, third and fourth visits, subjects will arrive following a 24-48h abstention from caffeine, alcohol and vigorous exercise and an overnight fast (8h). Participants will undergo three modified oral glucose tolerance tests (OGTT), following administration of either a water placebo (control), a caffeine-free CCED (control) or a caffeine containing CCED (5mg/kg caffeine) in a randomly assigned, double-blind, crossover design. Briefly, subjects will arrive and a baseline blood sample will be obtained (numbing cream will be offered). This will be immediately followed by administration of the treatment. Following a 30min absorption period, a standard OGTT (75g Trutol) will be administered. Additional blood samples will be obtained at 0, 30, 45, 60, 90, and 120min and assessed for glucose, insulin, fatty acids and C-peptide employing standard chemistry procedures. A peripheral IV will be used to obtain the 7 samples reducing needle pokes to one, ideally. Trials will be separated by at least 1wk, but not more than 4wk. Blood samples collected during the OGTT (all time points) will be assessed for metabolic and satiety signally hormone responses (ie. insulin). All subjects will also be asked to provide a saliva sample for genetic analysis. Genetic analysis will be performed by the company 23 \& Me. Subjects will also be asked to provide a midstream urine sample 30 minutes prior to the completion of the OGTT (90min time point +/10 mins). This is to allow for the analysis of caffeine and caffeine metabolites present in the urine, which will give insight into how caffeine is metabolized and excreted differently among individuals.