As coffee devotees, we all know there’s a lot going on in our cups. There in the deepest dark, notes of chocolate and fruit, nut and spice, both bitter and sweet swirl together in a mélange of epicurean wonder so profound that no other beverage can compete. And, of course, all that flavor comes with the boost provided by our favorite fuel, the celebrated compound called caffeine.
In a word, perfect.
Caffeine gives coffee its zoom, and coffee gives it to us. Yet the question remains: Just how exactly does it work this black magic?
The story is all in our heads. And it starts with a chemical called adenosine. As our neurons send signals to one another to create thought and consciousness, adenosine is created along the way. This adenosine attaches itself to special receptors on our brain cells. As we think, more adenosine is produced and more receptors get filled. Each time one does, its host nerve cell slows down its activity. Eventually, enough cells slow to create drowsiness, and we fall asleep.
Adenosine is the brain’s off-switch. It tells us when we’ve had enough thinking for one day and should hit the bed.
Enter caffeine, which is shaped and sized so much like adenosine that it can fit into those special adenosine receptors, too. But caffeine is an imposter. It looks like adenosine. It binds to our neurons like adenosine. But it doesn’t slow down their activity like adenosine. When it attaches to brain cells instead, real adenosine is blocked and that action keeps our nerve cells firing on all cylinders to make us feel less sleepy than we otherwise would.
It takes about four cups of coffee to block about half of the brain’s adenosine receptors, and the artificially boosted nerve activity that follows tricks the pituitary gland into thinking there’s some kind of crisis happening. It reacts by releasing adrenaline, our body’s emergency response hormone.
Now we’re not sleepy, our minds are going full tilt, and we’ve gotten a subtle rush of adrenaline. So far so good. But caffeine has another trick up its sleeve. It also stimulates the release of dopamine, the brain’s “feel good” chemical, and that elevates our mood along with the rest. This effect is what makes coffee mildly addictive and what makes us grouchy when we go decaf.
Caffeine’s adenosine mimicry has some byproducts of its own. When we drink coffee frequently, our brains develop more adenosine receptors in response, and over time, it takes more caffeine to keep us awake. When that caffeine is finally metabolized by our bodies, all the adenosine that’s just been hanging around with nowhere to go comes rushing back in to bind to all our receptors at once. What happens next is your coffee crash!
Going slow and taking it easy can prevent that crash and coffee’s other downsides, as well. As in all things, it’s just a question of moderation, which will let us have our caffeine and enjoy it, too!