Caffeine evolved in certain plants—including coffee shrubs, tea trees, cocoa beans, and kola nuts—as a naturally occurring pesticide to discourage insects from eating them. Stupid bugs. But that doesn’t explain why about 85 percent of Americans consume it in some form each day. (I can only assume that the other 15 percent have no quality of life whatsoever.) The reason is this: When caffeine is ingested, it quickly enters the brain, where it competes with a chemical called adenosine. One of adenosine’s most important jobs is to make you feel tired. Throughout the day, you produce a lot of it to make you eventually relax; neurons shoot it out, and then a receptor, perfectly sized to the adenosine molecule, binds to it, receiving the message that bedtime is approaching.
That’s where caffeine comes in. It is shaped very similarly to the adenosine molecule, so it fits into the receptors. The adenosine can’t park where it’s supposed to, because caffeine is already sitting in its parking spots. (That “first sip feeling” Starbucks advertises on the side of its cups sounds a lot more appealing than “blocking morning adenosine,” but that’s what’s really happening.) In truth, caffeine doesn’t pep you up—it simply prevents you from feeling lethargic. Consume enough caffeine, and you’ll have almost no adenosine plugging into your receptors at all, so you’ll feel wired and jittery.
To get to what really matters, though: Coffee makes you happy. Writing in the journal Psychopharmacology, the researcher David M. Warburton observed what I could have told him without writing a study: A low dose of caffeine can lead to a “significant increase in … happiness and calmness and decreases in tenseness.” He also noted that, among the study participants, these effects did not come from alleviating a craving from a caffeine addiction; the effect was true, pure, and wonderful. A miracle, really.
Caffeine is a gift in ways besides happiness. Combined with exercise, it can improve cognitive performance (that means it makes you smarter, in case you haven’t had your coffee yet), and if you’ve been sleeping less than optimally, it can enhance your reaction time and logical reasoning abilities. Remember this as you head out in traffic: The life your coffee saves could be your own.
Nothing in life is free, of course. Faced with the holy power of the Bean, adenosine’s malevolent forces fight back. As you consume more caffeine over time, adenosine receptors upregulate, increasing in number to accommodate the caffeine molecules and take in their intended guests as well. This leads to a state of tolerance, in which caffeine has a smaller effect after chronic use. However, this “problem” is really just an opportunity to enjoy more coffee.
Some people believe that the solution to tolerance is to hit the reset button. My wife is one of them: Recently, noticing the increases in my consumption over the years, she innocently proposed that I “take a little break” from coffee. The very suggestion made me fly into a rage. “Here’s an idea,” I replied, heart rate soaring. “Why don’t we just live apart for a year so it feels more like it did when we were first married?” An overreaction? I think not.
I’m at peace with the long-term effects of my devotion to coffee. Sure, my coffee habit is withering my hypothalamus and enervating my adrenal glands, forcing me to take in ever more caffeine as the years go by. But it is well worth it: Research from Japan shows that habitually drinking coffee reduces all-cause mortality. Studies in mice suggest that it does so by, among other things, encouraging autophagy, the biological process of cleaning out cellular trash, which naturally slows as we age. Coffee has also been found to reduce levels of fatty acid in the plasma of aged mice, which has been linked to diabetes and cancer in humans. (People say animal testing is cruel, but if it means giving mice tiny cups of coffee, I am all for it.)
Assuming that coffee does keep me alive for an extra few days or decades, I know how I’ll spend them: drinking more coffee, of darker and darker roasts, whose strong smell helps combat age-related loss of taste and smell. If Starbucks introduces a line of beans called “Indonesian Ashes,” I will be first in line to buy it.
