Coffee is one of the most popular drinks in the world, yet a surprising number of myths still surround it. Some sound logical: darker coffee seems stronger, espresso is intense, and freshly roasted beans should taste best straight away. The trouble is that flavour, caffeine content and quality don’t always work the way intuition suggests.
Below we take on five of the biggest coffee myths, without oversimplifying the subject, but without unnecessary theory either.
Myth 1: espresso has the most caffeine
Espresso tastes intense, has a dense body and comes in a small volume. It’s easy to assume that also makes it the coffee with the most caffeine. That’s only true if you compare drinks millilitre for millilitre. The caffeine concentration in espresso is high, but the shot itself is small, usually around 25 to 40 ml.
A large mug of filter coffee has a lower concentration, but it holds far more liquid. As a result, the whole serving can deliver more caffeine than a single espresso. The final figure depends on the dose of ground coffee, the species, the brew ratio, brew time and the size of the drink.
So it’s not worth judging a coffee’s “strength” by flavour intensity alone. Bitterness, a heavy body and a strong aroma are not a direct measure of caffeine content. If you want to cut down on caffeine, pay attention to the dose of coffee and the volume you drink rather than the taste.
Myth 2: the darker the roast, the more caffeine
Dark-roasted beans are associated with strong coffee because they bring more bitterness, roasted notes and a heavier aroma. That doesn’t automatically mean more caffeine. Caffeine is fairly resistant to roasting temperature, so the difference between light and dark roasts is usually much smaller than the flavour would suggest.
How you measure the beans matters too. During roasting, coffee loses water and some mass while the beans expand in volume. That makes dark-roasted coffee less dense. If you measure by volume, with a scoop for example, you’ll get a different result than if you use a scale. At home and in a café, the sensible approach is to weigh the beans. That way you’re comparing the actual dose, not its apparent volume.
Dark roasting mainly affects the flavour profile. More bitterness doesn’t mean more caffeine, just as the gentler taste of a light roast doesn’t automatically make it “weaker.”
Myth 3: robusta is sour
Robusta is often described as strong, intense and bold. Sometimes all of that gets lumped together and labelled “sour.” That’s a mistake. Acidity and bitterness are different taste sensations, even though people new to coffee often mix them up.
In the cup, robusta usually has lower and less complex acidity than arabica. What it shows more often is pronounced bitterness, a heavier body, and notes of cocoa, spice, wood and roasted nuts. It’s this strong, bitter or slightly astringent character that can be mistaken for sourness, even though it’s a completely different sensation.
That doesn’t mean every robusta is completely free of acidity. Flavour depends on origin, how ripe the cherries were, processing, roast profile and brewing method. A sharp, sour taste can also come from under-extraction, for example too coarse a grind, water that’s too cool, or too short a brew time. It’s not something you can pin on the species alone. You can also check which whole bean coffees are the least acidic.
Good-quality robusta used in an espresso blend can boost intensity, give the drink a fuller body and build a lasting crema without any dominant acidity. That’s why it often ends up in coffees meant for bean-to-cup machines, espresso machines and moka pots.
Myth 4: coffee tastes best straight after roasting
Freshly roasted coffee is a better choice than beans that have sat on a shop shelf for months. But “fresh” doesn’t mean “brewed a few hours after coming out of the roaster.” Freshly roasted beans hold a lot of carbon dioxide, which is released gradually. We call this process degassing.
Too much gas can get in the way of even extraction. In espresso, it often causes unstable flow, an overblown crema and difficulty dialling in a recipe. In pour-over methods, very fresh coffee “blooms” intensely, and the water can end up with poorer contact with the grounds.
Coffee needs a rest, then. There’s no single correct number of days for every bean. Roast level, density, brewing method and packaging all play a part. Filter coffee often starts tasting good after a few days, while espresso beans may need around 7 to 14 days. These aren’t fixed rules, just a practical starting point.
The roast date still matters a great deal, but it’s not a race. Well-packaged coffee has an optimal window, not a single perfect day.
Myth 5: coffee flushes magnesium and iron out of your body
This popular claim lumps two different things together, which leads to the wrong conclusions. Magnesium and iron don’t behave the same way in the body, and the word “flushes out” is an oversimplification in both cases.
Caffeine can briefly increase how much magnesium is excreted in urine, especially after a larger dose and in people who don’t drink it regularly. That doesn’t mean a few cups of coffee automatically causes a deficiency. The scale of this loss is small, and the drink itself also contains magnesium. Research reviews suggest that at typical intake levels, coffee can even be a small extra source of magnesium in the diet. What matters far more is your overall daily diet.
Iron works differently. Coffee doesn’t remove iron that your body has already absorbed. The polyphenols in coffee can reduce the absorption of non-haem iron, the type found mainly in plant foods, if you drink coffee alongside a meal. The effect depends partly on what’s in the meal and how many polyphenols are involved. Adding milk doesn’t solve this, but vitamin C improves the absorption of non-haem iron.
For a healthy person with a balanced diet, none of this is a reason to give up coffee. But if you have a diagnosed iron deficiency, low ferritin, or you’re taking an iron supplement, don’t wash it down with coffee and avoid drinking coffee right alongside a meal that’s an important source of iron. In that case, the timing and any supplementation are best worked out with your doctor.
Why do coffee myths stick around?
Most myths start from an observation that contains a grain of truth. Espresso really does have a high caffeine concentration, dark coffee really does taste intense, and the roast date really does matter. The mistake happens when we start treating one variable as a simple answer to every question.
Good coffee needs the whole picture: the quality of the green coffee, the roast, freshness, grind, water and recipe. You don’t need to know the full chemistry of extraction. It’s enough to stop following slogans on the bag and start paying attention to taste, changing one variable at a time.
If you’re after freshly roasted beans, choose your coffee to match your equipment and preferred flavour profile first. In the Colbergcoffee shop you’ll find coffee for espresso machines and moka pots, as well as light-roasted beans for pour-over methods.
FAQ: coffee myths
Does espresso have more caffeine than filter coffee?
Espresso has a higher caffeine concentration per millilitre, but it’s served in a small volume. A large serving of filter coffee can therefore contain more caffeine than a single espresso. The dose of coffee, the species and the recipe all play a part too.
Does dark-roasted coffee have more caffeine?
No. A darker roast brings more bitterness and roasted notes, so the coffee can seem stronger. But the actual difference in caffeine between light and dark roasts is much smaller than the flavour suggests.
Is robusta sour?
Robusta usually has lower, less complex acidity than arabica. It’s more often defined by strong bitterness, a heavy body and slight astringency, which get mistaken for sourness. A sour taste can also come from under-extraction.
How many days after roasting does coffee taste best?
There’s no single number that fits every coffee. Beans for pour-over methods often need just a few days’ rest, while espresso coffee can reach a more stable flavour after around 7 to 14 days. Roast profile, the beans themselves and how they’re stored all matter.
Does coffee flush out magnesium and iron?
Coffee doesn’t automatically remove magnesium or iron from the body. Caffeine can briefly increase magnesium excretion, while polyphenols can reduce the absorption of non-haem iron if you drink coffee right alongside a meal. If you have an iron deficiency, keep a gap as advised by your doctor.
