For many students, picking up a coffee from the dining hall before pulling a late nighter at the library is all too familiar. I will admit, I’m an energy drink fiend. My friends have commented on the frequency and quantity of caffeine that I consume during the academic year. “How are you still alive?” is a question I have been asked many times, so I decided to take a look at the science. Which being still alive, I am able to do.
As most people’s drug of choice (over 90% of adults, to be specific), caffeine acts as a central nervous system stimulant. It makes you feel alert, awake, and can even promote short-term memory. Caffeine is found naturally in various plants, seeds, fruits, and nuts, the most common being the coffee bean. The average drinker consumes about 200 mg of caffeine per day, which equates to about two cups of coffee.
Let’s crunch the numbers — how much is too much? A lethal amount of caffeine is about 180 mg/L, which has been determined by examining the blood of patients who died from overdose. When you consume ~100 mg of caffeine, it raises your blood caffeine levels by about 5 mg/L, meaning it’ll take almost 40 cups of coffee to be lethal. It’s also important to consider that caffeine takes as little as 15 minutes to take effect and has an average half-life of five hours. Half-life is a measure of how quickly your body eliminates a certain substance; if you have your typical 200 mg, then wait five hours, you will still have 100 mg left in your system. Because your body is constantly metabolizing, you would also need to get those coffees down within a few hours for it to kill you. Weight, other medical conditions, and genetics also play a role when it comes down to how caffeine reacts in your system, so lethal dose can vary greatly from person to person. To keep things simple, most scientists define the lethal dose to be 10 grams. Let’s use that for our calculations.
If we take a look at the selection of products offered in McGill cafeterias, we can start to crunch the numbers. The classic Roddick Roast coffee has 140 mg in a 6 oz cup. Coca Cola has 34 mg in a 12 oz can. When it comes to tea, a black (orange pekoe) tea has 34 mg for a 6 oz cup, and a bottle of Pure Leaf iced tea has 69 mg for 18.5 oz. Your yellow can of Yerba Mate has 150 mg in 15.5 oz, and the skinny white can of Mate Libre, about 55 mg per 11 oz. Finally, kombuchas can contain caffeine. The amount differs by brand and flavor, but Rise Kombucha’s rose flavor has about 8 mg per 7 oz. Around exams, I’ve seen the Awake chocolate bars too, which boast 114 mg of caffeine for a 44 g bar.
The bottom line is it’s highly unlikely that you’ll reach a lethal dose from consuming caffeine in your beverages. The number of cases of caffeine overdose as a result of coffee or energy drink consumption is low. Instead, most cases are linked to anhydrous forms of caffeine — whether it be pills or powders. In dry form, as little as a tablespoon of caffeine powder can be lethal.
While caffeine overdose is possible, it’s not likely when it comes to coffees, teas, or even energy drinks. So, your drink lineup from Royal Victoria College is very unlikely to kill you, but still, you don’t want to give it a try.
Cat Wang recently graduated from McGill University with a Bachelor of Science (BSc) degree in the anatomy and cell biology program.