Photograph by Sam Abell, National Geographic
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Close view of coffee being poured into a glass cup.
Photograph by Sam Abell, National Geographic
The Plate

Caffeine: The Buzz That Keeps Us Coming Back

March is Caffeine Awareness Month, and – depending on what and who you read – it’s either time to up your coffee intake or drop it altogether in favor of fruit smoothies or herbal tea.

Caffeine – though certainly not the most flashy – is possibly the world’s most popular psychoactive drug. People have been hooked on it for at least 5,000 years, ever since the legendary Chinese emperor Shen Nung – also known as the “Divine Farmer” – discovered naturally caffeinated tea.

The ancient Mexicans were getting a caffeine buzz from cacao at least 3,500 years ago, according to Murray Carpenter’s comprehensive Caffeinated; and coffee has been with us since at least the 9th Century when – according to Ethiopian lore – a goatherd named Kaldi saw his flock get frisky after eating some mysterious red berries. Sampling some for himself, he found that coffee had the same giddy effect on people.

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A blooming coffee tree bears blossoms and berries at the same time. Photograph by Luis Marden, National Geographic

About 90 percent of Americans consume caffeine every day, variously in the form of chocolate, tea, coffee, sodas, and energy drinks. Dunkin’ Donuts and Starbucks together sell a mind-boggling 26 million cups of coffee daily – enough to fill four Olympic-sized swimming pools; and worldwide, we gulp down 20,000 Coca-Cola drinks a second – a whopping 1.7 billion a day.

To feed our caffeine habit, the United States imports some 3.5 billion tons of coffee beans and 285 million pounds of tea each year. There’s a lot of caffeine going down our collective pipes.

About sixty different plant species produce caffeine, which functions in nature as an insecticide, protecting plants from munching pests. In human consumers, caffeine has a host of other effects. Among others, it perks us up, enhances our mental and physical performance, speeds up our reaction times, boosts our short-term memory, focuses our attention, and makes us feel springy and energetic.

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Tasters sample coffee brews before prescribing their blend. Photograph by Sam Abell, National Geographic

Caffeine has supported generations of students through stressful exam weeks; and has long been known as a means of upping physical endurance. Tea-drinking Tibetans, for example, once fed their horses and mules tea before embarking on strenuous journeys through the mountains. Distances were routinely measured in cups of tea: a three-cup journey was a trek of five miles. And people aren’t the only ones who seek it out. Bees have a far better memory for plants that offer a slug of caffeine in their nectar. Check out National Geographic’s Bees Buzzing on Caffeine.

Athletes love caffeine, which is often touted as the world’s most popular performance-enhancing drug. It inhibits the sense of fatigue, makes people stronger and faster, and – the icing on the cake – it’s legal. In a 2009 overview of 21 studies of caffeine and timed competitions in athletics, researchers found that in sports ranging from running to rowing, cross-country skiing, and cycling, caffeine consistently improved performances. In some cases, caffeine upped performance by as much as 3 percent – which, in the tightly timed world of sports, is enough to make the difference between glorious victory and ignominious defeat.

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Women harvest tea leaves on a hillside near the Caspian Sea in Iran. Photograph by James P. Blair, National Geographic

Similarly, soldiers in the field – who have to stay awake, keep focused, and move fast – do better when caffeinated. The army supplies caffeine through a variety of field-tested products, among them Military Energy Gum (each stick contains 100 mg of caffeine, about as much as is found in the average cup of coffee), caffeinated energy bars, and caffeinated tube foods – think chocolate pudding with a kick – for pilots.

All these benefits, though – the faster, stronger, smarter, and more energetic you that emerges from your cup of morning joe – come with a price. Most obvious of these is sleep disruption: the caffeine that wakes us up can also make us sleep-deprived. Caffeine doesn’t disrupt REM (Rapid Eye Movement) sleep like alcohol does; instead it appears to interfere with stages three and four sleep, the periods when we get our most restful and restorative down time. The result can be a vicious circle, as groggy people chug more caffeine to wake up during the day, then experience increasingly disrupted nights.

On the other hand, not everyone reacts to caffeine in the same way. On average, the half-life of caffeine in the human body is about five hours – that is, it takes five hours to flush out 50 percent of the caffeine in your system.

The rate at which caffeine is metabolized, however, can vary depending on body weight, genetic luck of the draw, lifestyle, and even what you had for lunch. Women on birth control pills, for example, take longer to metabolize caffeine, and so get more mileage out of a cup of coffee or a bottle of caffeinated soda; smokers, on the other hand, metabolize caffeine twice as fast as normal, and so get less of a buzz. Cruciferous veggies, like cabbage, broccoli, and cauliflower, increase the rate of caffeine metabolism; apiaceous veggies, like celery and carrots, decrease it, causing caffeine to hang around longer.

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Photograph by Rebecca Hale, National Geographic

Some studies even show an effect of personality type. Are you a gregarious extrovert or an introverted loner? Research indicates that extroverts get more of a cognitive boost from caffeine than introverts do. There are also differences in caffeine effect depending on chronotype – that is, when do you prefer to get up in the morning? Larks – naturally early risers – seem to be more sensitive to the sleep-disrupting effects of caffeine than night owls are.

Over the past three decades, over 19,000 scientific papers have been published on the effects of caffeine. Various studies have shown that caffeine can alleviate migraines and ward off depression, lower the risks of contracting Type 2 diabetes, heart disease, and certain kinds of cancers, stave off Parkinson’s and Alzheimer’s, and even, possibly, increase life expectancy.

Caffeine – at least in mice – protected test subjects from developing multiple sclerosis.

Coffee consumption appears to inhibit DNA strand breakage caused by free radicals – sinister offshoots of normal body metabolism that, if left to their own devices, can wreak biological havoc. Damaged DNA can lead to accelerated aging and increase the risk of cancer.

In many cases, however, the caffeine picture is confusing; and scientists hasten to point out that correlation does not necessarily mean causation. There’s also the chance that other molecules may be weighing in here. Coffee, for example, as well as caffeine, contains a huge number of different compounds, among them a handful of known carcinogens.

Caffeine may have benefits, but it also has a dark side. Just a tablespoonful of purified caffeine can kill you – though to get the same effect from coffee, you’d have to guzzle fifty brimming cups. More to the point, caffeine, in the susceptible, can trigger anxiety and panic attacks, and – in the rare, worst-case scenario – topple people into outright paranoia.

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A vendor at a market in Bahrain pours tea for a customer. Photograph by Steve Raymer, National Geographic

On the other hand, historically, caffeine looks pretty good. Bach, Beethoven, and Napoleon were all dedicated caffeine consumers; so was Voltaire, who claimed to owe his philosophy to coffee. Benjamin Franklin was a fan – coffee, he claimed admiringly, “excites cheerfulness without intoxication;” and the endlessly energetic Teddy Roosevelt is said to have put down a caffeinated gallon every day. Then again, there’s evidence that all that caffeine-fueled focus isn’t all it’s cracked up to be. Sometimes creativity and problem-solving are better served by a little loopy mind-wandering.

The bottom line? Caffeine is complicated and it’s clear that the votes aren’t all in yet. In the meantime, the American Medical Association recommends a cautious 300 mg of caffeine – say, two to three cups of coffee – a day.

UP Coffee is an app for monitoring your caffeine intake. Just be aware that this isn’t as easy as it sounds.

Got the jitters? Check out this graphic showing which products offer the most buzz. The Food and Drug Administration does not currently regulate caffeine in foods and drinks since caffeine has GRAS status – that is, it is “generally recognized as safe.” As manufacturers add more and more caffeine to foods, however, and serve caffeinated beverages in increasingly larger portions, concerns are on the rise about cumulative caffeine intake and its effects on health.