Probability of Exceeding Body-Weight-Adjusted Caffeine Thresholds in Adolescents from

What is the safe amount of caffeine for teenagers? Official guidelines say it should be based on a teen's body weight—not a flat daily limit like adults get. For example, Health Canada recommends a safe limit of 2.5 milligrams of caffeine for every kilogram a teenager weighs, while Europe suggests 3 milligrams.The big problem: It is incredibly hard for scientists to figure out what percentage of teenagers actually go over these safe limits on any given day. Why? Because everybody is a different size, everyone drinks a different number of drinks, and the amount of caffeine in a single can or cup can vary wildly (a green tea has very little, but a large energy drink has a ton!). Because all of these moving parts are mixed together and affect one another, you can't just solve this with a simple math formula.What this paper does: We built a virtual "simulation pipeline" using a computer method called Monte Carlo simulation. Think of it like rolling digital dice to simulate thousands of different teenagers' days. The computer virtually chooses a random body weight, randomly picks how many drinks they have (0, 1, 2, or 3), randomly selects a category (like coffee, tea, matcha, or energy drinks), and then adds up the total caffeine to see if that virtual teenager went over their safe weight limit.To make sure the computer wasn't making mistakes, we double-checked the work using three extra math tools:Sandbox Bounding: Calculating the absolute best-case and worst-case scenarios (like a heavy teen drinking only tiny teas vs. a small teen drinking multiple massive energy drinks) to make sure the simulation numbers always stayed inside logical boundaries.Smart Guessing (Logistic Regression): A math tool to see exactly how much your odds of going over the limit change with every extra kilogram of body weight or every extra energy drink you add.Caffeine Decay (Pharmacokinetics): A realistic test that factor in how the body naturally breaks down caffeine over a 5-hour half-life, tracking peak caffeine levels in the body rather than just adding everything up at the end of the day.What we found: When we ran the simulation using our placeholder test numbers, anywhere from 12% to 55% of our virtual teens went over the safe limits. It turned out that the official rule you choose to follow (like 2.5 vs. 5 mg/kg) impacts the results more than anything else, followed by how old the teen is. Interestingly, tiny label errors on energy drink cans barely changed the final results at all.Why it matters: The final percentages in this paper are just test numbers meant to prove that our code works. The real achievement is the code blueprint itself. Now, other scientists can take this exact computer pipeline, plug in real-world health survey data (like the US NHANES data), and instantly get accurate, real-world answers to keep teenagers safe.