Around 90% of Americans have some form of caffeine every single day [1]. But most people don’t know why that cup of coffee gets them going in the morning or how that energy drink makes it easier to power through work or school.

So, how does the most widely used psychoactive drug increases alertness and make you feel more awake? To answer that, we must take a trip under your skull (metaphorically, of course) to look at the effects of caffeine on the brain.

That trip begins with caffeine and a compound known as adenosine.

Adenosine: The Relaxation Molecule

Adenosine is a brain molecule that attaches to a brain receptor—called the A1 receptor—and promotes sleepiness and muscle relaxation.

Adenosine can also bind to another receptor—the A2A receptor—interfering with the release of dopamine (the “feel good” chemical) and other neurotransmitters that boost mood.

Adenosine is most present in your body at the end of the day. That’s because adenosine concentration is highest when you’re awake and increases the longer you’re awake. This can explain why you feel sleepier as the day wears on and are groggy when you wake up after a night of sleep.

Caffeine: The Adenosine Bully

Caffeine is like a bully to adenosine in the brain. Here’s how:

  • Caffeine’s chemical structure is very similar to adenosine, so it can compete with it and block it from binding to A1 receptors. This promotes wakefulness instead of sleepiness and prevents us from getting as tired.
  • Caffeine also blocks the A2A receptor so adenosine can’t reach it as it normally would. By blocking the receptor, caffeine supports a release of “feel good” dopamine and “excitatory” glutamate.
  • At the same time, caffeine prevents the reabsorption of dopamine into your system, meaning it hangs out longer and makes us feel good longer.

So with this information in mind, let’s look at how this works in a typical day…

Caffeine Through the Workday

While we use caffeine for a variety of reasons, such as for increasing alertness, boosting workouts, making up for lost sleep, or studying for an exam, this example shows the effects of caffeine on the brain from one cup of coffee during a typical workday.

Waking Up: Caffeine Consumption Begins

Through the night, your body has metabolized adenosine, and after you wake up and shake off the grogginess, you become more alert.

You walk to the kitchen and make a cup of coffee, which your small intestines absorbs in the next hour. It’s now usable by your body and brain.

As the caffeine reaches your brain, its molecules start competing with adenosine and blocking it from binding to receptors.

Mid-Morning: Caffeine Peaks

A couple hours after consuming the caffeine, your blood concentration of caffeine is at its highest. Adenosine is still blocked from reaching and binding to A1 and A2A receptors, and you feel most alert and “good” now. Great time to be productive!

Late Afternoon/Early Evening: When Caffeine Lays Off

As the day wears on, caffeine “gets tired” of blocking adenosine receptors and gets metabolized more. You might notice yourself feeling more tired or sleepy as the end of the workday gets closer.

Since most of the caffeine molecules aren’t in the way anymore, adenosine is able to bind to the receptors again. This makes you start feeling sleepy and relaxed.

Assuming you had the coffee in the morning, most of it is gone by early evening.

At night, as you get into bed to sleep, your resting body goes into recovery mode, metabolizing the adenosine molecules.

Rinse and repeat the next day.

Caffeine, whether it’s in the form of coffee, tea, chocolate, or energy drinks, is a handy tool to fight sleepiness and boost alertness during the day throughout the day. We developed our CCL Caffeine as a healthy source of caffeine (that you inhale!) without any crash or added sugars. Learn more about it here.