Written by Quinn Lui
Illustrated by Rebecca Michaels-Walker
Maybe you’ve started every morning with a coffee for years, or perhaps you reserve it for your most desperate all-nighters. Wherever you fall on that continuum, you’re not alone—on the average day, 71% of Canadian adults are taking a sip from at least one cup of coffee, and 48% are drinking tea. In comparison, tap water is drunk on a daily basis by about 63% of the adult population. At the same time, a significant number of those same adults either sleep poorly or for too few hours each night. Given caffeine’s reputation for waking you up, it’s no surprise that many of us rely on it. But have you ever wondered how exactly it works?
Adenosine, a type of molecule called a neurotransmitter, acts as a messenger in your nervous system. When adenosine binds to specific proteins in your body called A1 receptors, it sends the signal to your brain, and your brain activity slows down. As a result, your muscles relax and you begin to feel sleepy. This is great when you’re about to go to bed, but it can get in the way of completing last-minute assignments or staying awake through a three-hour class. That’s where caffeine comes in. It blocks the A1 receptors, preventing adenosine from doing its job. You’re able to stay awake and alert—for a little while, at least. As the amount of caffeine in your body decreases over the next few hours, adenosine begins to bind to the now-empty receptors, and you’ll start to feel tired again.
Besides increasing your wakefulness, caffeine’s ability to block adenosine comes with physical advantages like pain relief. Other effects take place in your nervous system, too: the presence of caffeine starts a chain reaction that activates the production of adrenaline, which causes your fight-or-flight response to kick in. A heightened level of adrenaline is what grants coffee drinkers short-term benefits such as improved attentiveness and reaction time.
However, the more caffeine enters your system, the less significant its effects become, and a high dose can also increase symptoms of anxiety. Furthermore, while caffeine can help you stay up late, sleep is necessary for breaking down the adenosine left in your body at the end of the day. Skipping sleep by drinking coffee will only make adenosine build up and continue to affect you later. Over time, you might even wind up experiencing caffeine withdrawal after spending a couple days without it. Symptoms can include fatigue, headaches, nausea and trouble concentrating. It’s no wonder that most people who develop a caffeine dependency will stick to their daily cups of coffee—the consequences of giving it up would reflect exactly what they wanted to avoid when they started drinking it.
The precise way that caffeine affects more complicated brain functions like your decision-making and problem-solving abilities is still unknown, and for the most part, the research surrounding its long-term effects on health also fails to reach clear conclusions. Caffeine has been shown to potentially lower your risk for developing Alzheimer’s disease, type 2 diabetes, various cancers, and other conditions, but the evidence behind these findings usually isn’t convincing enough to draw bold conclusions. However, a stronger association has been drawn between caffeine consumption and complications during pregnancy. Overall, drinking no more than three to four cups of coffee per day is considered more likely to help than harm!