Understanding the science behind your coffee fix

There is a reason that the coffee queue at the Student Union Memorial Center might be longer than usual during the final weeks of a semester. As deadlines loom, we rely on a jolt of caffeine to give us a lift for a few hours.

But what does a cup of coffee do to our brain?

Research shows that the relationship between coffee and cognitive performance is more nuanced than we thought. Whether you're cramming for exams in the library or grading papers in your office, the effect of caffeine is not just about making you feel alert – it also affects your memory and mental performance. 

In this Q&A, psychology professor Lee Ryan explains the relationship between circadian rhythm and the time of the day at which you drink coffee. Ryan, who researches the neurological basis of memory and memory disorders, talks about some surprising health benefits that might help you feel better about reaching for coffee in between classes or meetings. 

Image

How did your research interest in coffee and its effects begin?

I am interested in anything that benefits memory, particularly as we age. A few years ago, some undergraduate students in my lab became curious about caffeine's impact on the brain. Our experiments revealed that caffeine does benefit memory performance, but with an interesting twist: It works most effectively during your nonoptimal time of day, essentially bringing your performance back to your peak level.

We all have circadian rhythms that determine when we're at our cognitive high and low points. Interestingly, these rhythms shift as we age. For younger people, like college freshmen and sophomores, the optimal time is typically late afternoon. We know that teenagers aren't fully awake in the morning. As you get older, this shifts. So by your 60s and 70s, over 85% of people perform best early in the morning.

So, does coffee affect different age groups differently?

Yes, in terms of timing. We found caffeine benefits young people most in the morning when they're tired, while older adults see the greatest benefit around 3 to 4 p.m. The good news is you don't need a large amount. We gave participants just an 8-ounce cup with a typical caffeine content, not an extra-large Starbucks.

While we test the long-term effects of caffeine specifically, we know caffeine's half-life – the time it takes for half of it to clear from your system – is about four hours. For younger people, it's faster, around two hours. As you age, clearance time slows, which is true for all drugs. The effects likely last several hours, enough to get you through that low point in your circadian rhythm.

What exactly happens in the brain when you consume coffee?

Caffeine increases overall brain activity in a fairly nonspecific way. We tested memory specifically, but it likely affects other cognitive functions similarly. It's comparable to what athletes experience: Caffeine can push performance higher, not dramatically but noticeably, probably through similar mechanisms in both the brain and body.

Coffee has numerous health benefits beyond alertness. The coffee bean contains anti-inflammatory and antioxidant properties. Interestingly, research consistently finds protective effects. Studies show caffeine may help protect against Parkinson's disease, Alzheimer's disease and even certain cancers in the digestive system.

Is it the smell, taste or something else that makes coffee effective?

That's a great question. While many people love coffee's taste, caffeine itself is what provides the cognitive benefits regardless of the source – whether it's coffee, tea or other caffeinated drinks. Coffee's popularity is partly cultural – it's integrated into how we socialize and work. Some people don't enjoy coffee's taste, which is often genetically determined by sensitivity to bitter flavors. What we experience as "flavor" is actually a complex combination of taste and smell working together.

Are there any side effects to be aware of?

The most significant concern is sleep disruption if you consume caffeine at the wrong time. This is especially important for older adults since their caffeine clearance time is longer. Even afternoon coffee might interfere with their ability to fall asleep. It's about finding that sweet spot – enough caffeine for benefits without disrupting sleep.

Is there a recommended daily amount of coffee that's considered safe?

While I don't have specific guidelines on maximum safe amounts, moderation is key, especially when considering potential sleep disruption. In our research, we used a moderate amount – about what you'd find in a typical 8-ounce cup of brewed coffee.