This episode is also on Bilibili too.
Today I want to talk to you about an English-language book I recently finished reading, This Is Your Mind on Plants. I’m going to use this book to chat about how caffeine has changed the human mind—and even changed the course of human history.
We know that some plants affect our psychology and alter our mental states. The examples we’ve probably been hearing most about lately are the red umbrellas and white stalks—some wild mushrooms with hallucinogenic effects, meaning they make people see things that aren’t there. We often hear about people in Yunnan accidentally eating these red-umbrella, white-stalk mushrooms, then seeing lots of little people dancing in front of them, and finally being sent to the hospital for gastric lavage.
For most of us, poisonous mushrooms like these are just something to talk about over tea, seemingly far removed from everyday life. But actually, plants that alter the mind are right beside us, affecting the daily lives of almost every one of us.
For example, have you had coffee or milk tea today? If you have, then your mental state isn’t exactly a normal one. You’re watching this episode with a mind that caffeine has already altered. Caffeine is the most widely consumed psychoactive substance in the world today. Around 90% of people on Earth regularly take in caffeine through drinks like tea and coffee, and most of them are addicted to it—without caffeine, they can barely function. Caffeine is also the only psychoactive substance we routinely give to children, mainly through cola and chocolate.
So, if 90% of humanity is almost constantly in a state of having its mind influenced by caffeine, can we really say that humans rule the Earth today? Maybe that statement is incomplete. The complete version should be: The Earth is actually ruled by humans with caffeine flowing through their veins. Humans and caffeine co-rule the world!
And caffeine doesn’t just affect people today. In the past, it also had an enormous impact on the course of human history.
We know that changes in human society have always been closely tied to certain important plants. For example, the reason humans were able to move from a primitive hunter-gatherer lifestyle into agricultural civilization was that we discovered staple crops such as wheat and rice. Without plants suitable for cultivation, agricultural civilization would never have emerged.
Have you ever wondered: if agricultural civilization was created by plants like wheat and rice, was there a plant that created the modern world we live in today, a world centered on industrial civilization?
The plants that created this modern world may well be coffee trees and tea plants—the two main plants that produce caffeine.
Without the caffeine supplied by these plants, the modern world we live in today might never have come into being.
So how did that happen? I got this idea from This Is Your Mind on Plants. I’ll unpack it in detail in a moment. First, let’s talk about what kind of book this is.
The author has quite a résumé. His name is Michael Pollan. Pollan was originally one of the very best food writers around. His earlier works won the James Beard Award—often called the Oscars of food—multiple times. In 2009, Michael Pollan was selected by Newsweek as one of the ten leading thinkers, and in 2010 Time named him one of the 100 most influential people in the world. His books on food, The Botany of Desire and The Omnivore’s Dilemma, are already available in Chinese editions. If you’re interested, you can look them up.
But I’m not sure what happened later: Pollan, this food writer, became fascinated with things that can alter the human mental state. In 2018, Pollan wrote a book called How to Change Your Mind. In it, he introduced the past and present of hallucinogens such as LSD and psilocybin, and recorded his own firsthand experiences trying various hallucinogens in the spirit of Shennong tasting every herb himself. After publication, the book received rave reviews and topped bestseller lists across the United States. I previously did a detailed guide to it on my audio program Psychology New Knowledge Class.
And This Is Your Mind on Plants is Pollan’s second round of deliberately courting disaster.
In this new book, Pollan once again channels the reckless spirit of Shennong tasting every herb himself, getting up close and personal with three plants that can alter the human mental state. Which three? The poppy, coffee, and the San Pedro cactus. Poppies contain opium, a depressant; coffee contains caffeine, a stimulant; and San Pedro cactus contains mescaline, a hallucinogen. Depressants, stimulants, and hallucinogens are exactly the three major categories of psychoactive substances.
This Is Your Mind on Plants is divided into three sections, each describing Pollan’s intimate encounter with one of these three psychoactive substances. In the first section, Pollan tries to grow poppies at his home in California, nearly getting arrested by the U.S. police and almost turning himself into a walking legal cautionary tale. In the final section, Pollan joins friends at a Native American religious ceremony in an Indigenous community. The ceremony has a history of thousands of years. Local Indigenous people have long drunk a beverage made from San Pedro cactus during it, getting woozy and experiencing all kinds of hallucinations—either to heal emotional wounds or to induce religious experiences. Michael Pollan also drank the cactus beverage at the ceremony he attended and experienced a psychedelic journey that sent his mind soaring beyond the ordinary world.
The most distinctive part of the book is the middle section—the caffeine section—which is an encounter in reverse. Like most of us, Michael Pollan is also addicted to caffeine, so in this section he tries to quit his caffeine habit and see what happens to him.
I think this is also the most valuable section of the book. The other two are basically creative nonfiction, mainly telling stories. But Pollan spends relatively little space on his own experience in the caffeine section; what he talks about most is the history and science of caffeine. It’s a popular-science essay about how caffeine affects our psychology, and even how it has affected the course of human history.
So, what I’m going to do next is talk to you about this caffeine section—how caffeine changed the human mind and, in turn, helped bring the modern world into existence.
I’ve organized this part of the book around five relationships.
1. Caffeine and Mind Control
2. Caffeine and the Enlightenment
3. Caffeine and the Industrial Revolution
4. Caffeine and Globalization
5. Caffeine and Health
These five relationships stretch in sequence from ancient times all the way to today.
1. Caffeine and Mind Control
Let’s start with caffeine and mind control.
When it comes to the relationship between caffeine and humans, the first question we need to ask is: why do some plants produce chemicals like caffeine that can alter an animal’s mind?
Here’s how it happened:
Molecules that alter an animal’s mental state originally began as defensive tools used by plants. Caffeine, for example, is an alkaloid. Alkaloids are generally bitter; they’re biological toxins. Their original function was to stop insects and animals from eating plants. If the animals insisted, the alkaloids would poison them to death.
But killing those animals isn’t necessarily the best evolutionary strategy for a plant, because it can easily select for animals that are resistant to the toxin—just as our use of antibiotics today selects for superbugs. So, in some plants, what ultimately won out through evolution wasn’t an alkaloid that could kill animals outright, but an alkaloid that could alter animal behavior. These alkaloids are relatively less toxic, making it harder to select for ultra-resistant animals, while still effectively getting rid of them.
For example, some alkaloids make insects behave recklessly. An insect that would normally stay put starts wandering around after eating the plant, and before long a bird spots it and eats it. See? Plants can use alkaloids to get someone else to do the killing for them. Pretty clever, right?
But there’s something even cleverer. In war, why wipe out all your enemies? Wouldn’t it be more profitable to capture them and make them work for you?
Some alkaloids really did evolve the ability to control animals and make them serve the plant. Caffeine belongs to this category of alkaloids.
In the 1990s, German researchers discovered that the nectar of some citrus plants (Citrus) also contained caffeine. But what was caffeine doing in flower nectar?
Scientists later found that the caffeine in nectar wasn’t there to drive insects away. It was there to attract them. Experiments showed that when a little caffeine was added to nectar, bees that had visited that nectar once were more likely to remember its flavor—and more eager to return to it.
In other words, the caffeine in nectar could actually get bees addicted. A caffeine-containing flower is like a drug dealer: once a bee is lured into taking its first hit, it can never really leave the dealer alone. It keeps coming back, craving another taste.
Caffeine’s appeal to bees is extremely strong. Later experiments found that even when a flower no longer had any nectar, the bees would still keep returning to it.
So who benefits from this relationship? Obviously, the plants whose nectar contains caffeine. They use caffeine to control the bees’ behavior, getting them to pollinate the plants willingly. In this relationship, the bees are essentially slaves, exploited workers. They may even produce less honey because they become too fixated on these caffeine-containing flowers.
It’s hard not to draw a parallel: could we humans who love coffee so much actually be just like these bees? Are we a bunch of oversized bees? Could we humans also be slaves whose minds are controlled by caffeine?
This question needs to be considered from two angles.
For one thing, coffee trees and tea plants have certainly benefited from humans’ love for them. There’s no doubt about that. Coffee trees and tea plants originally grew in scattered pockets of one or two regions of the Earth, but after humans fell in love with caffeine, coffee and tea plants—especially coffee trees—spread all over the world. From an evolutionary perspective, these plants’ genes spread across the globe thanks to human affection. That is, of course, a huge success. From this angle, humans are caffeine’s slaves.
So, from the human point of view, are we simply being exploited by caffeine, or are coffee and humanity actually achieving a win-win? Are we ourselves getting enough benefits from caffeine?
This question can be analyzed from both a macro and a micro perspective. We can ask, on the macro level, whether caffeine has been a blessing or a curse for human civilization. And on the micro level, we can ask whether caffeine benefits or harms an individual’s physical and mental health.
So let’s start with the macro level: can caffeine really influence human civilization?
The answer is, it seems, yes. The modern world we live in today, built on industrial civilization, actually has a great deal to do with caffeine.
How did industrial civilization first emerge? It had two major sources. Its intellectual source was the Enlightenment, which arose in Europe in the 17th century. The Enlightenment discovered the value of rational thought and established a spirit of reason, greatly promoting the later development of science, technology, and modern forms of social organization. The other source was the 18th-century Industrial Revolution, which brought many new technologies and a new mode of production based on factories.
And caffeine was intimately connected with both of these great sources of modern society: the Enlightenment and the Industrial Revolution.
Let’s first look at the relationship between caffeine and the Enlightenment.
2. Caffeine and the Enlightenment
Coffee came from the Arab world to Europe in the 17th century, on the eve of the Enlightenment. Europe’s first coffeehouse opened in Venice in 1629. That was the late Ming period in China, the second year of the Chongzhen reign. After that, coffeehouses quickly blossomed across European cities.
You may have read in history books that from then on, coffeehouses became melting pots where new ideas, cultures, and institutions were incubated. Anyone could sit in a coffeehouse, exchange news and experiences, and make ideas collide.
Newton and Halley discussed their discoveries in physics and mathematics in coffeehouses; British writers like Jonathan Swift and Daniel Defoe chatted about everything under the sun in coffeehouses, eventually using this language to transform English literature; some of Britain’s earliest stockbrokers traded shares in a coffeehouse, which later developed into the London Stock Exchange; and later still, Parisians gathered in a coffeehouse to hatch the plan to attack the Bastille.
Coffeehouses provided a completely new kind of public space, advancing the Enlightenment’s new ideas and driving the various intellectual and social changes that began in the 17th century. But this may count only as an indirect push from caffeine toward those social transformations.
Caffeine’s more direct effect on Europeans at the time was probably psychological, because caffeine is a remarkably powerful stimulant. It raises and sustains alertness, keeps people from getting sleepy, sharpens concentration, speeds up thinking, improves memory, and heightens vigilance—and those are exactly the mental conditions required for rational thinking.
Coffee may have let Europeans, drowsy for centuries, collectively feel for the first time: Wow, so this is how good clear thinking feels!
—That sounds a little like a joke, doesn’t it? But it’s not as absurd as it sounds. Before coffee became widespread, Europeans had already been drinking wine and beer for several hundred years. Before coffee and tea appeared, Europeans drank alcohol in the morning, at noon, and at night—not only in taverns after dark, but also at home with breakfast, and even at work. For medieval Europeans who drank wine and beer like water, opportunities to think clearly were actually pretty scarce. If you’ve watched Game of Thrones, which is modeled on medieval Europe, you have some idea what I mean. The people in it almost never drink a drop of water; adults and children alike drink alcohol.
In fact, among the world’s three great centers of civilization over the past thousand-plus years—Chinese civilization in the East, Arab civilization in the Middle East, and Christian civilization in Europe—the Europeans’ mental state was consistently the worst.
In Chinese civilization, tea began spreading during the Tang dynasty, which also happened to be a golden age of Chinese civilization. I don’t know whether that was a coincidence.
In the Arab world, Islam prohibited alcohol, so alcohol had very little impact on Arabs. And from the 15th century onward, coffee became widespread in the Arab regions.
Only the miserable Europeans had nothing but alcohol. Medieval Europeans were, in reality, drunk Europeans.
Against this background, it’s easier to understand how huge a shock the arrival of coffee was for Europeans in the 17th century.
The historian Jules Michelet, known as the “father of French historiography,” was a caffeine fanatic. He once wrote: “Coffee, the sober drink, the mighty nourishment of the brain, which unlike other spirits, heightens purity and lucidity; coffee, which clears the clouds of the imagination and their gloomy weight; which illumines the reality of things suddenly with the flash of truth.” It lets people see, lucidly, “the reality of things.”
In Michelet’s view, coffee, along with the microscope, telescope, and pen, became an indispensable tool for humanity’s march toward rationalism. The difference was that the other tools were held in the hand, while coffee was a tool that worked inside the brain. The German historian Wolfgang Schivelbusch also said: “With coffee, the principle of rationality entered human physiology…”
These historians may have exaggerated somewhat. After coffeehouses rose, wine and beer certainly did not disappear from European life. But European thought does seem to have been liberated from alcohol’s grip; coffee gave the European mind more time in a clear-headed state, making it possible for Europeans to embrace reason.
Actually, alcohol and coffee really are somewhat opposed in the way they affect the human mind. Alcohol is a narcotic that suppresses the capacity for rational thought; what it stirs up is romanticism. As the saying goes, “Li Bai could write a hundred poems after drinking a dou of wine.” Once the wine gets you feeling good, you write poetry and express your romantic feelings.
But what if Li Bai had drunk a dou of coffee instead of a dou of wine? He probably would have written a hundred argumentative essays, and China might have entered the Enlightenment directly during the Tang dynasty. Just kidding. Anyway, what coffee stimulates is rationalism.
In fact, many of the thinkers in the European Enlightenment were coffee fanatics, and fanatical to a degree unimaginable today. For example, Voltaire, the grand master of the Enlightenment, was a passionate coffee devotee. Apparently, he drank 72 **cups of coffee a day!** Please, nobody imitate him. He was a rare genetic specimen; that kind of drinking will kill you.
All in all, coffee may indeed have helped give birth to the Enlightenment and rational thought. On the other hand, coffee also became deeply involved in another foundation of the modern world—the Industrial Revolution.
That brings us to the third relationship: caffeine and the Industrial Revolution.
3. Caffeine and the Industrial Revolution
The Industrial Revolution was first and foremost a technological revolution: machines such as steam engines and spinning machines replaced human labor. For workers operating in front of machines, a brain numbed by alcohol became a huge threat to safety and productivity. When people worked in small workshops, they could have a drink, chat, and then hammer metal while smelling of alcohol, and still get the job done. But factory workers really needed coffee and tea. They had to stay focused at all times to keep up with the machines’ pace, or something was bound to go wrong.
Capitalists were also pursuing efficiency. Factories commonly operated 24 hours a day, and many workers had to work night shifts for long periods—something unimaginable before caffeine became widespread. Human beings are not very good at changing their circadian rhythms for long periods through willpower alone. With caffeine, however, staying up late to work became possible.
Later, as industrial production grew more complex, factories developed many jobs involving mental labor—accountants, managers, and so on. To do that kind of work, people had to remain extraordinarily clear-headed, making caffeine indispensable to these new occupations as well.
So you see, without caffeine, even if the technology of the Industrial Revolution had existed, there would have been nobody to adapt to it.
Thus, during the Industrial Revolution, caffeine became a tool for capitalists to control workers. It helped workers keep up with the machines and made them more productive, ultimately allowing them to make money for capitalists more efficiently. From this angle, caffeine was a curse: it warped the human mind and made humanity better suited to the demands of the new economic order that emerged after the Industrial Revolution.
Next came another wave, sweeping across the world right after the Industrial Revolution: globalization. The Industrial Revolution triggered a huge leap in transportation technology. Trains and steamships made long-distance trade more profitable, and a global trade network took shape. Caffeine, surprisingly, also played a substantial role in that round of globalization.
This is the fourth relationship we’re going to discuss: caffeine and globalization.
4. Caffeine and globalization
As I mentioned, after the Industrial Revolution, workers developed a huge demand for caffeine. But coffee cultivation was not yet as widespread as it is today, and coffee was expensive. Europeans therefore urgently needed a cheaper source of caffeine—especially Britain, the birthplace of the Industrial Revolution, where the demand was even more pressing.
This problem was not solved until the first half of the 18th century, when the British discovered tea in China. Starting in the first half of the 18th century, the British East India Company began trading regularly with the Qing government, and tea replaced coffee as the main vehicle for delivering caffeine into European veins. By the early 19th century, from aristocrats to commoners, hardly a Briton was left who didn’t drink tea.
What happened next is a story we Chinese know all too well. Since the Qing government had little interest in British goods, the tea trade created a huge British trade deficit with China. The British East India Company eventually came up with the dirty trick of smuggling opium to reduce the deficit.
As a result, at least several million Chinese people became addicted to opium, and the various humiliations China suffered in modern times began here. The most ironic thing is that tea is a stimulant that can make thinking more agile, while opium is tea’s exact opposite: a sedative that makes thinking dull and numb.
Michael Pollan writes in the book: “For the English to sharpen their minds with tea, the minds of the Chinese had to be clouded with opium.”
When I read this sentence in the book, I got goosebumps all over. It sparked a thought: **I feel that the trade cycle between China and Britain, from tea to opium, was like Britain performing a gigantic spell—the spell was a kind of soul-sucking magic stretching across the Eastern and Western Hemispheres, siphoning away the clear-mindedness of the Chinese and injecting it into the minds of people in Britain on the other side of the world.** After this spell, the British were all bright-eyed and bushy-tailed, while the Chinese became vacant-eyed and dazed, as if the British had sucked out the souls of the Chinese.
To get caffeine, the British also incurred another moral debt. In China, the birthplace of tea, people didn’t mind tea’s bitterness. The British of that era, however, minded it very much, so they drank tea with sugar. Thus, alongside the tea trade, the sugar trade began to flourish. One of sugar’s main uses in Britain at the time was as a flavoring added to tea. But back then, nowhere else in the world could produce sugar on the scale that China could produce tea. So, across Central and South America, huge plantations were opened to grow sugarcane. Who planted the sugarcane? Slaves transported from Africa. Scholars estimate that 70 % of the slave trade was used to support sugar production. In other words, the slave trade was closely tied to the sugar trade, and the source of the sugar trade was, in fact, still Europeans’ obsession with caffeine. Yet back then, few Europeans who drank tea and coffee knew that their clear-headed, rational way of life was built on the brutality of the slave trade.
So you see, **caffeine consumption profoundly changed Europe, profoundly changed the East, and profoundly changed the Americas.** We said at the beginning that the modern world may have been created by caffeine. Doesn’t that claim sound a little less exaggerated now?
There’s another bit of gossip we can chat about concerning caffeine’s impact on the Americas. During the American Civil War, the Union and Confederate armies had one enormous difference: the Confederate army couldn’t get coffee because its economy was completely blockaded. Supposedly, this seriously damaged Confederate morale, while the Union army had coffee in abundance. Each year, the Union army gave every soldier 36 pounds of coffee—enough to go around. The Union commanders also understood coffee’s effects perfectly well. One Union general even weaponized it, ordering soldiers to drink coffee before battle. So, **stimulated by coffee, the Union troops were bright-eyed and bushy-tailed, while the coffee-deprived Confederates were yawning their heads off.** I don’t know whether that was one of the reasons the Union ultimately defeated the Confederacy.
At this point, we’ve sorted through caffeine’s effects at the macro level, especially some of its major impacts on modern civilization. Can we answer the question now—has caffeine been a blessing or a curse for human civilization? I’m afraid we still don’t have an answer.
Caffeine unquestionably helped bring this modern world into being. In many ways, this world is of course extraordinary: human technology and culture have flourished as never before. But this world also has plenty of problems, and humanity paid many terrible prices on the way to establishing this world order. Has caffeine been a blessing or a curse for human civilization? It’s complicated.
So let’s finish by looking at the slightly more straightforward micro level. At the micro level, do coffee’s mental and physical effects on each of us do more good than harm, or more harm than good?
This is the last relationship we need to discuss: the relationship between coffee and health.
5. Caffeine and Health
Historically, coffee has faced all kinds of accusations over its effects on health. But the amazing thing is that, to date, caffeine has escaped almost all of the serious charges.
As for coffee’s effects on health, the current scientific consensus is more than reassuring—it is downright cause for celebration. Current research shows that coffee and tea not only aren’t harmful to our health, but may also bring some important benefits.
Of course, the proviso is that you don’t overdo it. But how much is too much? The scientific recommendation is no more than 400 milligrams of caffeine a day. That’s roughly equivalent to three shots of espresso or two large Starbucks Americanos. My own daily coffee intake is about that much right now.
As long as you stay below that limit, drinking coffee and tea offers the following benefits: regular coffee drinking can reduce the probability of developing many types of cancer, including breast, prostate, colorectal, and endometrial cancer; caffeine can also lower the risk of cardiovascular disease, type 2 diabetes, Parkinson’s, and Alzheimer’s; there is even evidence that moderate coffee consumption may reduce the risk of depression and suicide; and coffee and tea are also rich in antioxidants, which have many benefits for the body.
But (unfortunately, there is a but here), all of these benefits of coffee may be completely wiped out by one harmful effect. What harm?—It interferes with sleep.
Once caffeine enters the body, one of the most important biochemical reactions is its binding to adenosine receptors in the central nervous system. Adenosine is a psychoactive compound in the brain. When its concentration in the brain is high, you feel alert. Once it binds to receptors and its concentration drops, you start to feel sleepy. This is normally part of our sleep mechanism: when we get tired from working, more and more adenosine binds to receptors, we start feeling sleepy, and then we go to sleep, restoring the adenosine concentration. But after we take in caffeine, those receptors are occupied by caffeine molecules, leaving adenosine floating free. So we stay wide awake.
So caffeine’s most important and direct effect on the human body is actually to disrupt our normal sleep rhythm and force us to stay awake.
For people who need to stay functional during the day, this interference may be helpful. But there is a serious problem: caffeine is metabolized much more slowly than we imagine. Many people think that having some coffee or tea during the day is no big deal, as long as they don’t drink any at night. In reality, for most people, it takes 12 hours for 75% of caffeine to be metabolized. In other words, if you finish your coffee at noon and go to bed at midnight, 25% of the caffeine is still in your body. This means that the overwhelming majority of people who habitually drink tea or coffee are sleeping with their sleep mode seriously disrupted.
This leads to a serious lack of deep sleep and overall sleep time. Matthew Walker, a sleep expert at the University of California, Berkeley, said: “If you plotted the increase in the number of Starbucks cafés over the past 35 years against the increase in the number of people getting insufficient sleep during that period, the curves would look remarkably similar.”
We all know that many people around the world have sleep problems today. Phone screens, noise pollution, and the stresses of life may all bear some responsibility, but in Matthew Walker’s view, caffeine must be added to that blacklist.
There is now ample scientific evidence that insufficient sleep seriously threatens people’s health. Sleep deprivation may be a key trigger for Alzheimer’s, atherosclerosis, stroke, heart failure, depression, anxiety, suicide, and obesity. In other words, caffeine’s health benefits may ultimately be canceled out by its serious negative effect on sleep.
I mentioned earlier that Michael Pollan writes in the book about his own attempt to quit coffee. During the period when he successfully quit, one of his most important experiences was a huge improvement in sleep quality: he slept deeply and for a long time.
Of course, he eventually started drinking coffee again. After all, that fresh, energetic feeling you get from coffee is still wonderful—and for a mental worker like him, that state is indispensable.
If you’re someone who habitually drinks coffee, none of this is meant to tell you to quit completely. The takeaway we get from the book is actually very simple: control the total amount of coffee you drink, and more importantly, drink it only in the morning.
So, at the micro level, we can say that drinking coffee and tea does more good than harm, provided you consume them properly.
All right, with that, we’ve finished introducing the “caffeine chapter” of Michael Pollan’s book This Is Your Mind on Plants. Through five pairs of relationships, we’ve talked our way from caffeine’s evolutionary history to all its entanglements with humanity.
If you have any thoughts or questions about today’s content, you’re very welcome to leave a comment and discuss them.
I’m Zhichao Wei. If you enjoy my show, please follow, like, save, and comment. I’ll keep sharing new psychology insights on this channel. That’s all for today—see you next time.
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