Coffee is liquid magic in a cup.
However hard Monday mornings are, once you have that hot, steaming brew in your hand and the aroma hits your nose, everything starts to seem bearable.
By the time the cup is empty, you feel ready to face another week in the office.
So many of us rely on coffee to see us through the working week, but have you ever wondered how much caffeine is in coffee?
How many cups is it safe to drink per day? And what happens if you drink too much?
Here we have the answers to these and all your other caffeine-related questions.
What is caffeine and how does it work?
Most people are aware that coffee contains something called caffeine and that when you drink it, the caffeine has certain effects on your body. It gives you a pleasant “buzz” and helps you stay awake when you’re tired.
Before we discuss how much of this substance is found in different coffee drinks, let’s have a quick look at what caffeine is and what it does to you.
Caffeine is the most commonly used psychoactive drug in the world. In its pure state, it is a white powdered alkaloid. When ingested, the compound stimulates the central nervous system, increasing heart rate and blood flow, making you feel more alert and energetic (1).
Caffeine also temporarily blocks adenosine receptors in the brain. Adenosine is a substance the body produces naturally that carries signals that calm you down and make you feel ready for sleep.
When caffeine binds itself to the adenosine receptors in the brain, it prevents the action of adenosine, causing you to feel more awake and lively.
Caffeine also encourages the production of dopamine, resulting in heightened brain activity and even a feeling of mild euphoria. Caffeine can improve mental performance, increase concentration levels and even improve performance in physical exercise.
However, the bad news is, if you take too much of this drug in one go, the effects can quickly turn negative, with symptoms including anxiety, increased heartbeat, headaches, and insomnia.
If this all seems a little abstract, check out this great video that explains it all very clearly.
Warning: Per study from sleep educator Terry Cralle, coffee increases the frequency people visit bathroom, which may lead to dehydration.
And it can even creates a vasoconstricting effect, further compounding the problem, so that's the reason why some people feel sleepy after drinking too much coffee.
How much caffeine in coffee? No simple answer
With all this in mind, it is very reasonable to wonder just how much caffeine there is in your cup of coffee. Unfortunately, giving a straight answer to this question is not so simple – for several reasons.
In short, there are so many variables involved in making a cup of coffee that trying to give a definitive figure would be somewhat arbitrary and even a little pointless (though we will still try at the end of the article!).
The type of coffee, the origin of the coffee, the preparation method, the dose and even the person making it, among many others, can all affect the result.
What factors affect the caffeine content of coffee?
Here are some of the most significant factors affecting caffeine levels in coffee.
One of the two principal factors affecting the caffeine content is the species of coffee plant the beans come from.
There are many plants in the genus Coffea, but two species are grown commercially for coffee production, Coffea arabica and Coffea canephora (commonly known as robusta). They give us arabica and robusta coffee beans respectively.
Robusta contains about twice as much caffeine as arabica. This means coffee brewed purely from robusta beans will have a higher caffeine content than arabica coffee.
Even within these two species, there is a small variation in the levels of caffeine present between different varietals (different “breeds” of the same species). There can even be slight differences in the amount of caffeine in the beans of two of the same plants growing side by side.
The other major factor affecting how much caffeine ends up in your cup is the preparation method. There is a multitude of different ways of turning roasted coffee beans into the rich and aromatic drink we know and love, and each method delivers varying amounts of caffeine.
Two of the most common ways of making coffee is “brewing” (which here is intended to include drip coffee, percolator and French press methods) and the espresso method.
Many people imagine that a shot of espresso contains more caffeine than coffee produced by brewing – but this depends on your definitions.
Espresso is often made with high-quality robusta beans and espresso also uses a very fine grind of coffee (see below), both of which mean the resulting drink has a very high caffeine content. If you take a 1oz cup of espresso and a 1oz cup of brewed coffee, the espresso has far more caffeine.
However, since the size of a regular cup of brewed coffee is much larger than a 1oz espresso shot, in the end, if you drink brewed coffee, you are consuming more caffeine overall.
To put this in other terms, the espresso has more caffeine by volume but the brewed coffee has more caffeine per serving.
Longer brewing times allow more caffeine to be released, and brewing methods that require the water to be in contact with the coffee for longer generally (but not always) tend to produce beverages with a higher caffeine content.
All other things being equal, the longer you brew the coffee, the higher the caffeine content of the resulting drink. However, it is thought that 90% of caffeine extraction occurs in the first minute of brewing, so leaving it longer will only release limited amounts of extra caffeine while potentially spoiling the flavor of the beverage.
The finer the grind, the larger the surface area of the coffee, allowing more caffeine to be released into the drink. This means that if two coffees are brewed from the same beans under the exactly the same conditions but one using a finer grind, the coffee with the finer grind will have more caffeine.
It is important to remember that grind size is one of the most important ways we control the flavor of coffee during the brewing process. Using a finer grind in an attempt to increase caffeine levels may result in an inferior drink.
The temperature at which coffee is brewed has some effect on the amount of caffeine released, with higher temperatures delivering larger doses of caffeine.
The problem with higher temperatures is that other bitter compounds are also released, spoiling the flavor.
Cold-brewed coffee has a lower caffeine content than coffee brewed using hot-brewing techniques.
Amount of coffee used
Using a larger quantity of coffee will result in a beverage with a higher caffeine content, but the resulting flavor may be too strong.
Many people believe that coffee roast has a significant effect on the caffeine content. Some claim that dark roast beans contain higher caffeine levels; others assert that dark roasting destroys the caffeine and that lighter roasts contain much more caffeine.
The truth, however, is that the roast of the coffee has little or no effect on the caffeine content since the compound remains very stable at the temperatures to which coffee beans are exposed during the roasting process.
Examples of caffeine levels in home-brewed coffee
As we have explained, there are so many variables affecting how much caffeine ends up in your cup of coffee. For this reason, it is impossible to give exact amounts per cup. The following is an approximate guide that can help estimate how much caffeine you are consuming.
Amounts stated are per 8oz serving.
Drip or filtered coffee
French press coffee
Turkish or Greek coffee
Examples of caffeine levels in other coffee drinks as consumed at home
Caffeine content in the coffees of some major chains
Since major chains standardize their drinks ranges, it is easier to give a definitive value to the amount of caffeine found in a serving of any particular drink.
That said, there is still the possibility of slight variations, depending on factors like the batch of coffee and the individual barista.
Starbucks has an extensive coffee menu. The following is a selection of some of the more common beverages. Starbucks coffees are some of the most caffeinated of all high street brands.
Amounts are per 8oz serving unless otherwise stated.
75 mg (single shot)
75 mg (single shot)
Pike Place brewed coffee
#2 Dunkin’ Donuts
Per 10oz serving unless otherwise stated.
98 mg (single shot)
Per 12oz serving unless otherwise stated.
71 mg (single shot)
Is caffeine bad for you?
For many years, coffee seems to have been given a bad press. The accepted wisdom was always that coffee was harmful to your health, and the best advice was to consume it in moderation, if at all (2).
However, the good news for coffee lovers everywhere is that there is a growing consensus within the medical community that, far from being bad from you, coffee-drinking actually has wide-ranging health benefits. One of the major reasons for this is the caffeine it contains.
However, as mentioned earlier, caffeine is a psychoactive drug, and unsurprisingly, overindulgence can have negative side effects. So how much is a safe amount of caffeine to consume per day?
The answer to this question varies, depending on which authority you consult. At the lower end of the scale, some might advise no more than 300mg per day. Others suggest limiting caffeine intake to around 400mg per day, while a slightly higher 400-600mg may still be within healthy limits (3).
Safe daily amounts also vary from person to person. Larger people may be able to consume more without experiencing adverse effects and some people are just naturally more or less tolerant to caffeine than others.
It is also worth pointing out that high doses of caffeine are toxic, and in sensitive individuals, even in lower doses, caffeine can be fatal. Deaths from caffeine overdose from only a few highly-caffeinated beverages have been recorded.
The best advice is to use common sense when enjoying your brew. Be aware of what your body is telling you, and if you begin to experience side effects, you know it’s time to cut down. If you regularly drink around three to five cups per day, you should experience all the health benefits with no negative reactions.
Sometimes we all need a cup of coffee to give us a boost, whether it’s waking up early in the morning or keeping us awake late at night when we need to finish some urgent work or have to study for an exam.
When taken in moderation, caffeine has many positive effects on our bodies, and coffee-drinking should be encouraged, not frowned upon.
If you understand how much caffeine is in coffee and how much there is in different types, you can easily make sure you don’t drink too much.
How many coffees do you drink per day? What do you think is a good amount of coffee to consume per day? Have you ever drunk too much coffee? How did it feel?
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