Caffeine is one of the only drugs we embrace without guilt. We — the 87% of us who ingest caffeine — boast about being “so addicted,” duck out during work to get a fix and can’t even imagine the last time we didn’t start off the day with a hit.
“It’s the only drug that’s not really seen as a real drug, that doesn’t have a stigma. It’s one that many of us feel comfortable giving to our children in small doses,” says Murray Carpenter, author of Caffeinated, a tenaciously researched look into the physiology, psychology and commerce of caffeine.
And it is a drug — contrary to popular misconception. Though studies suggest that it can improve mood and concentration and increase life span, caffeine has a dark side, too — upping anxiety and sleeplessness in some, and even causing psychosis in a small minority.
“It’s a fantastic drug, but it amazes me that it doesn’t get much respect,” Carpenter says. “We consistently underestimate its role in our bodies, our brains and our daily activities.” We also underestimate how much we’re actually taking in.
A Starbucks grande bought at the same store during the same day might contain anywhere from 260 milligrams to 564 milligrams, depending on who is brewing the coffee and how much caffeine the beans contain. How much we weigh, our lifestyles and our genetic tolerance also contribute to how we digest caffeine.
In fact, our love for soft drinks might not be the only cause in the precipitous drop-off of coffee drinking, Carpenter explains.
Coffee consumption has fallen in tandem with smoking rates — and with reason. Smokers, because they activate a liver enzyme that digests coffee at double the rate of nonsmokers, need to drink twice the amount of coffee to get the same kick.
Women who are on birth control inhibit these same enzymes, which means they need half the amount of coffee to get their high.
“These are things that underscore that it is a powerful, important drug and each of us reacts differently to it. Most of us think of it as a mild stimulant, but is really is a powerful drug,” writes Carpenter.
A little biology here: Once the liquid hits your stomach, it takes 20 minutes until caffeine hits your brain. The small molecules easily pass the blood-brain barrier, blocking the uptake of the neurotransmitter adenosine, the chemical that tells the brain it’s tired.
Meanwhile, caffeine stimulates the central nervous system, increasing alertness, decreasing reaction time and sharpening focus. Blood pressure increases, as does heart rate and muscle response.
That’s one reason why so many athletes and soldiers use it — another is that it can increase athletic ability by 3%.
Dr. Mark Tarnopolsky at McMaster University in Canada found that caffeine increases the amount of calcium released inside our muscles, enabling them to work harder.
“So caffeine has the potential to help endurance athletes in two very different ways, in different parts of the body. The drug blocks adenosine’s ‘you’re getting tired’ mantra as it pours more coal on the intramuscular fires,” Carpenter writes.
Another byproduct of caffeine is that as it inhibits those adenosine neurotransmitters, others, like dopamine, increase.
In other words, a cup of coffee a day might help keep the shrink away.
A series of studies out of Harvard show a link between coffee drinking and depression in women, finding that those who drank the most (four or more a day) had the lowest rates of depression.
Coffee drinking might make you happier — and it also might make you live longer. Studies have shown a link between coffee-drinking and staving off Alzheimer’s and Parkinson’s. And a National Institute of Health study revealed that those who drank three or more cups a day had a 10% lower risk of death than those who did not.
Is it the coffee or the caffeine — or both? This is unclear. But what was clear is that the results “provide reassurance with respect to the concern that coffee drinking might adversely affect health.”
At too-high doses, though, many of the positives are reversed. Take a fatal dose — a mere tablespoon of pure caffeine — and the results are startling: “arrhythmia, tachycardia, vomiting, convulsions, coma and death.”
Withdrawal has its own familiar side effects, among them: inability to concentrate, headaches and flu-like symptoms. And it only takes a little — a mere daily regimen of 100 milligrams a day (or one chai-tea latte).
Thirteen percent of those who experience withdrawal reported “clinically significant distress or functional impairment.”
Sleep disturbance is one of the most chronically harmful side effects of caffeine users. Caffeine’s half-life — or the time it takes for levels to reach 50% — is four to five hours. That means if we have a cup at midday, we might still be feeling its residual effects if we try to get to bed at 10pm.
Anxiety in those with genetic predispositions is another widespread result of coffee use.
On the extreme and rarest end of the spectrum, excessive caffeine use can also lead to psychosis.
Olfactory hallucinations — the taste of “plastic or burnt coffee” — occurred in patients injected with 250 milligrams of caffeine in 1993. Another, led by a team of Greek researchers, found that when a man with a history of panic disorder was injected with 400 milligrams of caffeine, he had an auditory hallucination.
The most cited example of “caffeine-induced psychosis” was of a successful, 47-year-old male farmer. Though he had no history of psychiatric issues, he developed the belief that people were “plotting against him to drive him off his farm and take his land,” the study reads. He installed security cameras, stopped bathing and was placed on a slew of anti-anxiety meds.
He also drank between 12 to 36 cups of coffee day. Once he kicked that habit, all of the psychiatric symptoms stopped.
The message is clear, writes Carpenter: “Caffeine can really mess with your head.”
An unedited version of this story originally appeared on the
New York Post.