This is Your Mind on Plants

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Note: The following are excerpts from This is Your Mind on Plants by Michael Pollan.

Does Caffeine increase performance?

‍I found numerous studies conducted over the years reporting that caffeine improves performance on a range of cognitive measures—of memory, focus, alertness, vigilance, attention, and learning. An experiment done in the 1930s found that chess players on caffeine performed significantly better than players who abstained. In another study, caffeine users completed a variety of mental tasks more quickly, though they made more errors; as one paper put it in its title, people on caffeine are “faster, but not smarter.” In a 2014 experiment, subjects given caffeine immediately after learning new material remembered it better than subjects who received a placebo. Tests of psychomotor abilities also suggest that caffeine gives us an edge: In simulated driving exercises, caffeine improves performance, especially when the subject is tired. It also enhances physical performance on such metrics as time trials, muscle strength, and endurance.

Caffeine and creativity

‍Whether caffeine also enhances creativity is a different question, however, and there’s some reason to doubt that it does, Balzac’s fervent belief to the contrary. Caffeine improves our focus and ability to concentrate, which surely enhances linear and abstract thinking, but creativity works very differently. It may depend on the loss of a certain kind of focus, and the freedom to let the mind off the leash of linear thought.

Caffeine's effect on consciousness

‍Cognitive psychologists sometimes talk in terms of two distinct types of consciousness: spotlight consciousness, which illuminates a single focal point of attention, making it very good for reasoning, and lantern consciousness, in which attention is less focused yet illuminates a broader field of attention. Young children tend to exhibit lantern consciousness; so do many people on psychedelics. This more diffuse form of attention lends itself to mind wandering, free association, and the making of novel connections—all of which can nourish creativity. By comparison, caffeine’s big contribution to human progress has been to intensify spotlight consciousness—the focused, linear, abstract, and efficient cognitive processing more closely associated with mental work than with play. This, more than anything else, is what made caffeine the perfect drug not only for the age of reason and the Enlightenment but for the rise of capitalism, too.

Is the popularly of Caffeine a good thing?

‍I put the question of whether caffeine was a boon or not to Roland Griffiths during one of our Skype interviews. He had a tall Starbucks cup in front of him, and paused for a long time before answering. “Sure, given the way our culture works, that we have times we need to be awake and asleep and need to report to work at certain times. We’re no longer able to just respond to our natural biological rhythms, so to the extent that caffeine helps us sync up our rhythms to the requirements of civilization, caffeine is useful. Whether that’s helpful to our species is another question,” he finished, trailing off, but clearly implying it was not.

How does Caffeine work?

‍So how exactly does coffee, and caffeine more generally, give us what it gives us? How could this little molecule possibly supply the human body energy without calories? Could caffeine be the proverbial free lunch? Or do we pay a price for the mental and physical energy—the alertness, focus, and stamina—that caffeine gives us? To answer these questions, it’s necessary to understand something about the pharmacology of caffeine. Caffeine is a tiny molecule that happens to fit snugly into an important receptor in the central nervous system, allowing it to occupy it and therefore block the neuromodulator that would normally bind to that receptor and activate it. That neuromodulator is called adenosine; caffeine, its antagonist, keeps adenosine from doing its job by getting in its way.

Adenosine is a psychoactive compound that has a depressive and hypnotic (that is, sleep-inducing) effect on the brain when it binds to its receptor. It diminishes the rate at which our neurons fire. Over the course of the day, adenosine levels gradually rise in the bloodstream, and as long as no other molecule is blocking its action, it begins to slow mental operations in preparation for sleep. As adenosine builds up in your brain, you begin to feel less alert and a mounting desire to go to bed—what scientists call sleep pressure.

But when caffeine beats adenosine to those receptor sites, the brain no longer receives the signal to begin turning out the mental lights. Even so, the adenosine is still circulating in your brain—in fact, its levels continue to rise—but because the receptors have been hijacked, you don’t feel its effects. Instead, you feel wide-awake and alert. Are you really? Yes and no. How you feel is how you feel, it’s true, but as Matthew Walker, a UC Berkeley neuroscientist and sleep researcher, explains, since adenosine continues to build up, you’ve just been tricked by caffeine, which is hiding its existence from you, and only temporarily.

What I’ve described here is the direct effect of caffeine on the brain; the chemical also has several indirect effects, including increases in adrenaline, serotonin, and dopamine. The release of dopamine is typical in drugs of abuse, and probably accounts for caffeine’s mood-enhancing qualities—the cup of optimism!—as well as the fact that it is habit-forming. Caffeine is also a vasodilator and can be mildly diuretic. It temporarily raises blood pressure and relaxes the body’s smooth muscles, which may account for coffee’s laxative effect. (This could explain some of coffee’s early popularity; constipation was a serious matter in seventeenth- and eighteenth-century Europe.)

But what is unique about caffeine is the targeted way in which it interferes with one of the most important of all biological functions: sleep. Walker, in his 2017 book Why We Sleep, argues that the consumption of caffeine—the most widely used psychoactive stimulant in the world—“represents one of the longest and largest unsupervised drug studies ever conducted on the human race.” We now know the results of that study and, if Walker is to be believed, they are alarming.

Is Caffeine dangerous?

‍For as long as people have been drinking coffee and tea, medical authorities, as well as quacks of various persuasions, have warned about the perils to human health posed by these beverages, which is to say, the dangers of caffeine. And ever since the seventeenth century, when women worried about coffee’s effect on male potency, the presumption has been that there must be a problem. Perhaps because we believe more deeply in the iron law of compensation than in the possibility of a free lunch, researchers have undertaken a massive, worldwide, centuries-long search to pinpoint caffeine’s karmic payback—the way in which our fond habit must surely be killing us. Cancer? Hypertension? Heart disease? Mental illness? At one time or another, caffeine has been implicated in all these problems and a great many more.

And yet, at least till now, caffeine has been cleared of the most serious charges against it. The current scientific consensus is more than reassuring—in fact, the research suggests that coffee and tea, far from being deleterious to our health, may offer some important benefits, as long as they aren’t consumed to excess. Regular coffee consumption is associated with a decreased risk of several cancers (including breast, prostate, colorectal, and endometrial), cardiovascular disease, type 2 diabetes, Parkinson’s disease, dementia, and possibly depression and suicide. (Though high doses can produce nervousness and anxiety, and chances of committing suicide climb among those who drink eight or more cups a day.)

Coffee and tea are also the leading source of antioxidants in the American diet, a fact that may by itself account for many of the health benefits of coffee and tea. (And you can get these antioxidants by drinking decaf.)* My review of the medical literature on coffee and tea made me wonder if my abstention might be compromising not only my mental function but my physical health as well.

Matthew Walker on Caffeine's effect on sleep

‍But what is unique about caffeine is the targeted way in which it interferes with one of the most important of all biological functions: sleep. Walker, in his 2017 book Why We Sleep, argues that the consumption of caffeine—the most widely used psychoactive stimulant in the world—“represents one of the longest and largest unsupervised drug studies ever conducted on the human race.” We now know the results of that study and, if Walker is to be believed, they are alarming.

However, that was before I read, and then met and interviewed, Matt Walker. Why We Sleep is one of the scarier books I’ve read. Walker, an Englishman, is a compact and wired man—I would describe him as caffeinated except that I know he is not. He is single-minded in his mission: to alert the world to an invisible public-health crisis, which is that we are not getting nearly enough sleep, the sleep we are getting stinks, and a principal culprit in this crime against body and mind is caffeine. Caffeine itself might not be bad for you, but the sleep it’s stealing from you may have a price: According to Walker, research suggests that insufficient sleep may be a key factor in the development of Alzheimer’s disease, arteriosclerosis, stroke, heart failure, depression, anxiety, suicide, and obesity. “The shorter you sleep,” he bluntly concludes, “the shorter your lifespan.”

Matt Walker grew up in England drinking copious amounts of black tea, morning, noon, and night. He no longer consumes caffeine, save for the small amounts in his occasional cup of decaf. In fact, none of the sleep researchers or experts on circadian rhythms whom I interviewed for this story use caffeine.

I thought of myself as a pretty good sleeper before I met Matt Walker. At lunch he probed me about my sleep habits. I told him I usually get a solid seven hours, fall asleep easily, dream most nights. “How many times a night do you wake up?” he asked. I’m up three or four times a night (usually to pee), but I almost always fall right back to sleep.

He nodded gravely. “That’s really not good, all those interruptions. Sleep quality is just as important as sleep quantity.” The interruptions were undermining the amount of “deep,” or “slow wave,” sleep I was getting, something above and beyond the REM sleep I had always thought was the measure of a good night’s shut-eye. But it seems that deep sleep is just as important to our health, and the amount we get tends to decline with age.

During deep sleep, low-frequency brain waves set out from the frontal cortex and travel toward the back of the brain, in the process synchronizing many thousands of brain cells into a kind of neural symphony. This harmonizing of our neurons helps us distill and consolidate the blizzard of information we’ve taken in during the day. Memories are carried on these slow waves from sites of short-term daily storage to more permanent locations. Picture the mental desktop being cleared off and reorganized at the end of the workday, as the brain’s files are stowed in their proper place or trashed.

With all the interruptions I was experiencing, Walker guessed I was sorely deficient in deep sleep. “You probably want to address that.” That night he sent me a link for a supplement that purported to improve prostate function.

Walker explained that, for most people, the “quarter life” of caffeine is usually about twelve hours, meaning that 25 percent of the caffeine in a cup of coffee consumed at noon is still circulating in your brain when you go to bed at midnight. That could well be enough to completely wreck your deep sleep.

“Some people say they can drink coffee at night and fall right to sleep,” Walker said, a note of pity in his voice. “That might be the case, but the amount of slow-wave sleep will drop by fifteen to twenty percent,” he said. “For me to decrease your deep sleep by that much, I’d have to age you by twenty percent.” Which meant that that after-dinner espresso would give me the lousy night’s sleep of a man twelve years my senior. I pictured the anarchy of my computer’s desktop after a long day of work when I have neglected to perform any digital hygiene.

Caffeine is not the sole cause of our sleep crisis; screens, alcohol (which is as hard on REM sleep as caffeine is on deep sleep), pharmaceuticals, work schedules, noise and light pollution, and anxiety can all play a role in undermining both the duration and quality of our sleep. But caffeine is at or near the top of the list of culprits. Walker says, “If you plot the rise in the number of Starbucks coffeehouses over the past thirty-five years and the rise in sleep deprivation over that period, the lines look very similar.”

(I was relieved to learn that Walker has since eased up a bit on his condemnation of coffee. In a recent exchange, he suggested that the demonstrated health benefits of “moderate morning coffee use” might outweigh the cost to our sleep health. “After all,” he wrote, “life is to be lived to a degree!”)

Caffeine and sleep continued

‍The sleep issue suggests an answer to the conundrum of how caffeine could be a source of human energy. It only looks that way, because caffeine is simply hiding, or postponing, our exhaustion by blocking the action of adenosine. As the liver removes the caffeine from circulation, the dam holding back all that pent-up, still-mounting adenosine will break, and when the rebounding chemical floods the brain you will crash, feeling even more tired than you did before that first cup of coffee. So what will you do then? Probably have another cup

It appears that there is no free lunch. The energy that cup of coffee or tea has given you has been borrowed, from the future, and must eventually be paid back. What’s more, there is interest to be paid on that loan, and it can be calculated in the quantity, and quality, of your sleep.

Here’s what’s uniquely insidious about caffeine: the drug is not only a leading cause of our sleep deprivation; it is also the principal tool we rely on to remedy the problem. Most of the caffeine consumed today is being used to compensate for the lousy sleep that caffeine causes. Which means that caffeine is helping to hide from our awareness the very problem that caffeine creates.

Charles Czeisler, an expert on sleep and circadian rhythms at Harvard Medical School, put the matter starkly several years ago in a National Geographic article by T. R. Reid:

The principal reason that caffeine is used around the world is to promote wakefulness. But the principal reason that people need that crutch is inadequate sleep. Think about that: We use caffeine to make up for a sleep deficit that is largely the result of using caffeine.

Here’s what’s uniquely insidious about caffeine: the drug is not only a leading cause of our sleep deprivation; it is also the principal tool we rely on to remedy the problem. Most of the caffeine consumed today is being used to compensate for the lousy sleep that caffeine causes. Which means that caffeine is helping to hide from our awareness the very problem that caffeine creates.

Why is Caffeine in soda?

‍Caffeine is naturally present in coffee and tea, but typically is added to sodas—so why would soda makers do that? Especially in a beverage marketed to children? The industry has claimed (to the FDA and other regulators) that the caffeine is there as a flavoring, and that they add it for the note of bitterness the alkaloid provides. They actually say this with a straight face. In 2000 Griffiths’s lab easily undermined the claim with a double-blind taste test in which cola drinkers were asked to detect differences in colas, some caffeinated and some uncaffeinated. Most couldn’t taste the difference. And yet the six top-selling soda brands in the U.S. all contain caffeine (typically about as much as in a cup of tea). Griffiths says that if you pair caffeine with any flavor, people will express a preference for that flavor. “Just like when I say ‘I love the way Scotch tastes.’"

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Learn more about This is Your Mind on Plants on Amazon.

Buy This is Your Mind on Plants: Print | Kindle | Audiobook

If you enjoy this summary, please consider buying me a coffee to caffeinate my reading sessions.