Evrim Yazgin
Cosmos science journalist
Before you reach for that cup of coffee or tea, have you ever thought about whether that caffeinated beverage is good or bad for you?
Most of us will drink coffee or tea each day.
It helps keep us alert, especially in a world of the nine-to-five grind. Some workers rely on caffeine to get them through shift work and night shifts.
Many, like me, would just collapse in a heap if it weren’t for that liquid black gold to keep us peppy in the morning.
What is caffeine?
To get a better picture of how coffee or tea affects us, let’s examine the active ingredient: caffeine.
Caffeine is a drug. It’s a white, odourless substance known to chemists as 1,3,7-trimethylxanthine and is made up of 8 carbon, 10 hydrogen, 4 nitrogen and 2 oxygen atoms.
Caffeine occurs naturally in coffee beans, cocoa beans, kola nuts, and tea leaves.
It is an adenosine antagonist, blocking the A1, A2A, and A2B receptors in the brain and body to promote wakefulness. Normally, adenosine (a chemical compound with a similar 3D structure to caffeine) binds to its receptors, slowing neural activity and making you sleepy.
When caffeine, instead, binds to the receptors, adenosine is blocked and brain activity speeds up, making you feel more alert.
History lesson
Tea and coffee are the most common way for humans to get their caffeine fix.
Drinks made using coffee beans date back more than a thousand years to the coffee forests of the horn of Africa.
Legend says that, around 800 CE, an Ethiopian goat herder named Kaldi noticed his goats were energetic and didn’t sleep when they ate the coffee beans. Coffee then spread eastward to the Arabian Peninsula, reaching Yemen in the 15th century, and Egypt, Syria, Persia and Turkey in the 1500s. From their it made it to Europe and eventually the whole world.
But caffeine is also present in other beverages like tea, cola and even some foods like chocolate.
Is it bad for you?
Given how prevalent the drug is, are there negative side effects we should be worried about?
For one thing, it is an addictive substance. And the more you drink, the more you need.
“Our body tends to adjust to a new level of consumption,” Kitty Pham, a PhD candidate at the University of South Australia and expert in nutritional and genetic epidemiology, tells Cosmos. “Your body does develop a tolerance to the caffeine. So, you start to need to drink more and more to feel the same effect as before.”
Caffeine can also act as an anxiogenic – a substance that can trigger heightened levels of anxiety.
Pham notes some risks associated with too much caffeine consumption over a long period of time.
“Greater than 6 cups per day, we did see an increase in dementia risk,” she notes. “There’s also some research on how it might increase your cholesterol. There’s a substance in coffee called cafestol that can regulate your blood cholesterol. If you’re drinking too much coffee, it might be increasing your cholesterol. So, there are risks, but often they are at really high consumption.”
What’s the limit?
So, how much caffeine is too much according to science?
“That’s, the million-dollar question, isn’t it?” Pham laughs. “There’s a lot of varying research on it. It’s hard to tell a definite limit. But generally, most studies really agree that one to two cups of coffee, or an equivalent of 100 to 200 milligrams of caffeine is safe and okay.”
The average cup of coffee has about 100 mg of caffeine. On average, instant coffee with one teaspoon of powder contains about 70 mg of caffeine, while a coffee pod has 60–90 mg.
Other drinks containing might have even more caffeine, making it important to monitor your consumption more carefully.
A 355 mL can of Red Bull energy drink has more than 110 mg of caffeine. Meanwhile, an average bar of dark chocolate has about 70 mg of caffeine.
Many people are moving away from coffee to drinks like tea and matcha which may have additional health benefits. A 100-gram cup of black tea has only about 20 mg of caffeine, while matcha can have 140–170 mg of caffeine!
“Looking at the US, they usually recommend less than 400 milligrams. So overall, moderation and keeping your consumption to one to two cups – that’s what I’d recommend.”
Now that I’ve written about caffeine, I think I need another cuppa. It’s only my second of the day, I swear.
