Young lovers sit at a sidewalk café and sip espresso between kisses; a group of giggling cheerleaders head for a cooler filled with iced energy drinks; a group of happy kids swing jack-o’-lantern baskets filled with candy bars, including some of our own favorites from childhood. These familiar scenes—romantic, joyous, heartwarming—are hiding an uncomfortable truth in plain sight: these apparently healthy and wholesome people are, like most Americans, dependent upon a powerful psychoactive stimulant drug: caffeine.
Murray Carpenter, an investigative journalist and the author of Caffeinated: How Our Daily Habit Helps, Hurts, and Hooks Us, conservatively estimates that more than 80 percent of Americans are consuming caffeine in excess of 100 mg/day, and the Federal Drug Administration’s estimates are even higher. A 2010 FDA report suggests that approximately 90 percent of us are using caffeine on a daily basis, and at a dose of more than 200 mg. These estimates are based on self-report and may be even higher. This is because about 54 percent of users are getting caffeine in the form of coffee or tea, and the caffeine content of these products varies widely across types and brewing methods. Even in circumstances when it might seem reasonable to assume some degree of dose consistency, as when the same volume of the same type of coffee bean or tea leaf has been brewed in precisely the same manner, the caffeine yield of the beverage can vary widely as a result of inherent plant variability. An excellent case in point comes from a University of South Florida study in which a 16-ounce cup of “Breakfast Blend” coffee was purchased from the same Starbucks location every day for six consecutive days and then assessed for drug content. The same serving of the same beverage from the same store varied from 250 mg to 564 mg. This suggests that a loyal customer’s “regular” daily dose of caffeine is anything but “regular” and could, in fact, be twice as much one day than the next. Such variation can significantly affect how we feel, how we think, and how we function, and yet we often have no way of knowing how much we consume. Most of us don’t even think to ask the question.
The dose range for regular users of over-the-counter “energy” products, such as pills, capsules, and energy drinks, is equally variable because the assessed doses often fail to fall within 20 percent variance of the dose noted on the label. In a recent study, Pieter Cohen, MD, and his colleagues at Harvard Medical School assessed the drug content of caffeine-based energy products that were purchased in the PXs of various U.S. military bases. They found that only nine out of 20 such products were found to have accurate dose labeling—and these are the same products that are available at convenience and “nutrition” stores across the country. So while these products offer the consumer the illusion of accurate dosing, it is, in fact, an illusion.
Owning Our Addiction
Let’s assume, for the sake of this discussion, that a group of caffeine users were consistently consuming an accurately measured dose of 100 mg and then abruptly stopped this regimen. Based on his review of the literature, Carpenter estimates that almost all of them would experience symptoms of physical and psychological withdrawal including headaches, lethargy, and an inability to focus. In other words, most Americans are drug dependent. And while most of us freely admit to “loving” our morning coffee, or “craving” our Coke, or being unabashed “chocoholics,” few of us are willing to face up to the fact that, from a physiological perspective, we can be called addicts. Holding aside the question of whether or not anyone should be taking a daily dose of caffeine (or a daily dose of any psychoactive substance), it’s curious that there has been so little national discussion about the simple fact that the overwhelming majority of us do. It’s as if we’re in a collective state of denial about our habit—but why?
We humans are social beings. This means that we need to negotiate with one another, at least minimally, in order to survive and to reproduce. The surest way to hide something from others is to hide it from one’s self. So, over the course of our species’ evolutionary history, ancestral humans have evolved cognitive processes—a suite of cognitive self-deceptive mechanisms—that “hide” or “dress up” aspects of ourselves and our behavior that might be considered socially questionable and which usually operate outside of our conscious awareness. Dependency upon a drug—even one that has been found to have myriad positive effects, minimal negative effects (for most individuals), and is considered by the medical community to be generally safe—suggests a lack of self-control, and that can be unsettling to ourselves as well as to others with whom we associate. As Dan Ariely, a behavioral economist, puts it, “We usually think of ourselves as sitting in the driver’s seat, with ultimate control over the decisions we made and the direction our life takes; but alas, this perception has more to do with our desires—with how we want to view ourselves—than with reality.”
The most basic question is why are we are doing this particular drug? Caffeine certainly has its share of drawbacks. It blocks neural receptors in the brain that, when activated, signal that it’s time for us to sleep (adenosine receptors), so taking it too late in the day or in too high a dose can cause sleep deprivation and subsequent fatigue, even in individuals who are usually tolerant of the drug. And in sensitive individuals, caffeine can cause nervousness and anxiety. There is some evidence to suggest that the drug may also decrease bone mineral density, increase blood sugar levels, and cause dehydration.
Caffeine also has its benefits. It has been found to enhance memory and may lower the risk of developing Parkinson’s disease; it may stimulate the gallbladder and, as a result, reduce the risk of gallstones; it causes blood vessels to constrict and may relieve some types of headache pain; and it reduces inflammation and may help prevent certain types of cardiac illness.
But it’s unlikely that these drawbacks or benefits have much to do with our passion for caffeine. We love this drug because of the way it makes us feel. In Caffeinated, Carpenter relays this relevant quote from a recent psychological review: “There is ample evidence that lower doses of caffeine are reliably associated with ‘positive’ subjective effects . . . Subjects report that they feel energetic, imaginative, efficient, self-confident, and alert; they feel able to concentrate, and are able to work but also have the desire to socialize.” So, it’s no wonder why humans have used it for millennia.
Like Bees to Honey
What has befuddled researchers for years is the question of why this particular chemical substance—a methylated xanthine found in the leaves and seeds of tea, coffee, cacao, and various other plants—is so readily available in nature. In 1984, Dr. James Nathanson, a neurologist at Harvard Medical School, discovered that high but naturally occurring doses of the drug can disrupt insect behavior to the extent that it precludes their ability to successfully reproduce, so for decades we assumed that caffeine’s sole adaptive utility to the plants that produced it was as an intrinsic organic pesticide.
Then, just last year, Geraldine Wright, a honeybee brain specialist at Newcastle University, reported findings that suggest that the naturally caffeine-laced nectar of certain plants actually serves to enhance the learning process of honeybees. As she explains it, “The plant is using this as a drug to change a pollinator’s behavior for its own benefit.” Bees, it turns out, are significantly more likely to return to those plants that produce the drug-infused nectar. Wright’s research illuminates the evolutionary interaction between plants and pollinators, but it also underscores the striking similarity between the brain chemistry of animals across species.
Just as honeybees repeatedly return to plants that produce caffeine-laced nectar, those of us who are chronic caffeine users make a beeline to the coffee shop at the corner, or the refrigerator to grab a soda, or to whatever place provides us with our caffeine delivery mechanism of choice. Caffeine, like other stimulant drugs such as cocaine, is “rewarding.” Like cocaine, it increases activity in midbrain dopamine systems, and so consuming it tends to increase the probability that we’ll repeat the behaviors that led to our consuming it in the first place. If, as a caffeine user, this makes you feel a bit like a rat pressing a lever, it’s probably time to step back, try to get a better sense of how much caffeine you take on a daily basis, and assess the pros and cons of using the drug at all.
Click here to read Peggy La Cerra's interview with Murray Carpenter, author of Caffeinated: How Our Daily Habit Helps, Hurts, and Hooks Us.
Peggy La Cerra, PhD, is an evolutionary neuroscientist and co-author of The Origin of Minds: Evolution, Uniqueness, and the New Science of Self.