Updated March 21, 2025 at 2:30 p.m.*
HAMBURG — For years, coffee has had a bad reputation, but now science has begun to tell us otherwise. Packed with hundreds of plant-based compounds, coffee doesn’t just perk you up: it helps lower the risk of various diseases and may even slow down aging. To get the most out of it, though, your coffee routine matters. Studies show that roasting, brewing methods, and even the time of day of drinking it can make a difference. And when in doubt, it’s best enjoyed black.
You might assume coffee is just water, caffeine, and a few roasted aromas. In reality, scientists have identified hundreds of different compounds in your typical cup of java. Most are volatile aromatic substances, but many have bioactive properties, meaning they directly impact the body. Take polyphenols, for instance: these natural antioxidants help neutralize free radicals, those aggressive oxygen molecules that can damage DNA and proteins.
However, not every cup of coffee contains the same amount of polyphenols. Much of it comes down to the roasting process.
What does too much coffee mean?
Like many substances we consume, caffeine is all about dosage. In small amounts, it does exactly what coffee drinkers hope for: it wakes you up. This is because caffeine mimics adenosine, a neurotransmitter that signals fatigue. By binding to adenosine receptors, caffeine blocks this effect, making you feel more alert and focused.
But caffeine has another trick up its sleeve, it constricts blood vessels in certain parts of the brain, which is why it’s often included in painkillers to enhance their effectiveness.
However, too much caffeine (more than 200 milligrams per drink or 400 milligrams per day, according to studies) can trigger nervousness, anxiety, restlessness, and even insomnia. In extreme cases, it can be lethal, though that would require consuming around five to ten grams of caffeine in a short period: roughly 50 cups of coffee.
It’s the caffeine, baby
The German Nutrition Society estimates that three to four cups a day are safe – one to two for pregnant and breastfeeding women. The actual caffeine content in a cup, however, can vary widely. Arabica and Robusta beans, for example, have very different caffeine levels: Robusta contains nearly twice as much. This is largely because Robusta plants grow in warmer, more humid climates and need to fend off more pests, producing extra caffeine as a natural pesticide.
Even decaf is associated with lower mortality and a reduced risk of cardiovascular disease.
Caffeine metabolism also varies from person to person. Its effects can last anywhere from four to eight hours, though some people process it significantly faster, or much slower. Smokers, for example, metabolize caffeine up to 50 percent faster than non-smokers (N Engl J Med: Van Dam et al., 2020), whereas pregnant women and their unborn babies process it far more slowly. That’s why some people can drink coffee all day without any issue, while others struggle to fall asleep after a single cup in the afternoon.
Fortunately, caffeine isn’t necessary to reap coffee’s health benefits. Studies show that even decaffeinated coffee is associated with lower mortality and a reduced risk of cardiovascular disease. However, when it comes to protecting against Parkinson’s disease, caffeine appears to be the key factor due to its interaction with adenosine receptors.
Made for the morning
Timing matters, too. A recent study for European Heart Journal reinforces the case for drinking coffee in the morning. Among 40,000 participants, those who drank coffee before noon had the lowest risk of death: 12% lower than both non-coffee drinkers and those who drank it throughout the day. The theory? Drinking coffee too late can disrupt sleep, negating its benefits. A simple fix: switch to decaf in the afternoon.
And what about cream, oat, soy milk, as well as sugar and sweeteners in coffee?
But what’s the best way to make coffee? In a fully automatic machine, with a porta-filter, a mocha on the stovetop, or filtered? Scientists are primarily concerned with this question because of the cholesterol levels coffee can raise. The coffee oils kahveohl and cafestol are to blame.
Only one thing helps to remove these from the coffee: the classic paper filter, because they can’t pass through the small paper structures. Other types of coffee, such as Turkish mocha, which boils coffee grounds directly with water, French press, or espresso, contain higher levels of cholesterol-triggering components (Open Heart : Svatun et al., 2022 ; Medicinia : Hao et al., 2024).
Medium roast, good acidity
Depending on the variety, raw coffee beans contain anywhere from 4% to 12% polyphenols, mainly in the form of chlorogenic acid, which gives coffee its signature tartness. Robusta beans tend to have slightly higher levels than Arabica. But here’s the catch: the hotter the roast, the more chlorogenic acid is broken down.
That doesn’t mean you need to switch to green (unroasted) or lightly roasted “blonde” coffee, which many find too acidic. Coffee has a unique trait: the longer it’s roasted, the lower the acidity — but in the process, new compounds emerge, including melanoids, which also have antioxidant properties. Some polyphenols even seem to form primarily at the final stages of a long roasting process (Frontiers in Nutrition: Mestanza et al., 2023).
Considering all these factors, researchers suspect that the highest concentration of health-boosting compounds is found in medium-roasted beans (Food Science & Nutrition: Wu et al., 2022). In one study, for instance, beans roasted at 210 to 220 degrees Celsius (420 to 438 degrees Fahrenheit) showed the best results.
The problem? Most research focuses on drum roasting, the method used by traditional coffee roasters. In contrast, industrially roasted coffee is blasted at around 600 degrees Celsius (1,200 degrees Fahrenheit) for just a few minutes. How much of those beneficial antioxidants survive that process remains unclear.
Moderate coffee consumption has been linked to a reduced risk of cardiovascular disease.
Nevertheless, numerous studies and large meta-analyses suggest that coffee’s benefits extend far beyond its polyphenol content. Moderate coffee consumption has been linked to a reduced risk of cardiovascular disease, type 2 diabetes, dementia, Parkinson’s disease, and even lower overall mortality rates.
But there’s a catch: too much coffee can flip those benefits into risks. The key lies in finding the right balance and right quantity, which may largely come down to caffeine intake.
Hold the milk and sugar
That said, cholesterol levels in countries where filtered coffee is less common (such as Italy) are no higher than in places where it’s the norm. In other words, if your cholesterol is already high, switching to filter coffee might be a good idea. Alternatively, instant coffee is an option since it contains little to no cafestol or kahweol.
So, what does an ideal coffee-drinking day look like based on current research?
And what about cream, oat, soy milk, as well as sugar and sweeteners in coffee? A minority drink their coffee black. From a scientific perspective, this is where it becomes more difficult to assess. Of course, any sugar, milk, or vegetarian alternative means more calories are consumed. If these aren’t burned by the body, you can gain weight in the long run. Milk in coffee could also cause the proteins in it to bind the healthy polyphenols, making them less available. On the other hand, milk can neutralize stomach acid, making the coffee easier to digest for many people.
So, what does an ideal coffee-drinking day look like based on current research? A couple of cups of well-tempered black filter coffee made from medium-roast beans in the morning, followed by decaf in the afternoon. That said, the most important rule is probably the simplest: your coffee should taste good.
*Originally published March 17, 2025, this article was updated March 21, 2025 with enriched media.
