Coffee contains more than 1,000 chemical compounds, some of them bioactive. Caffeine, chlorogenic acids, trigonelline, cafestol, kahweol and melanoidins are just a few of them. Their concentration can change depending on the coffee's genetics, origin, processing, roast and brewing method. That's why, to understand how coffee may relate to our health, studying a single compound isn't enough: what matters is which coffee we drink, how much, how we brew it and who is drinking it.
When we think about what's in coffee, the first word that comes to mind is probably caffeine.
That makes sense. It's coffee's best-known compound and the one we tend to associate with that boost we look for in the morning.
But reducing coffee to caffeine is like trying to explain an entire book by reading just one of its pages.
Inside something as small as a coffee bean there is enormous chemical complexity. More than 1,000 compounds have been described, including caffeine, chlorogenic acids, trigonelline, diterpenes such as cafestol and kahweol, melanoidins and a huge number of compounds related to its aroma and flavour.
And the most interesting part is that this composition is not always the same. It changes from one coffee to another and keeps transforming until it reaches our cup.
So every time a new study comes out saying something about "coffee", there's a question we should ask first: which coffee are we talking about?
What compounds does coffee contain?
Coffee is a complex chemical matrix. Some of its components are already present in the green bean; others are transformed during roasting, and others appear precisely as a result of the high temperatures.
Caffeine. An alkaloid and coffee's best-known natural stimulant. One of its main actions is to block adenosine receptors, which are involved in regulating sleep and the feeling of tiredness.
Chlorogenic acids. A family of phenolic compounds found in coffee. They are being researched, among other reasons, for their antioxidant activity and their possible metabolic and vascular effects.
Cafestol and kahweol. Natural coffee diterpenes. Cafestol is especially interesting because human trials have shown that sufficiently high exposure can raise LDL cholesterol.
Trigonelline. Another alkaloid found in green coffee. During roasting, part of it breaks down and takes part in various chemical reactions, including those that produce aroma components and form niacin, a form of vitamin B3.
Melanoidins. These are generated during roasting through Maillard reactions. They contribute significantly to the colour and other characteristics of the drink and are also currently being researched for their biological properties.
And these are just a few examples. So the question is no longer simply "what's in coffee?" but a far more interesting one: what determines what ends up in our cup?
| Compound | What it is | Approximate amount | Main effect / interest |
|---|---|---|---|
| Caffeine | Alkaloid; coffee's best-known natural stimulant | 60–120 mg per cup of filter coffee (≈200 ml); 60–80 mg per espresso of 30 to 60 ml | Blocks adenosine receptors, which regulate sleep and the feeling of tiredness |
| Chlorogenic acids | Family of phenolic compounds | Around 70–350 mg per cup, depending on the bean and the roast | Studied for their antioxidant activity and possible metabolic and vascular effects |
| Cafestol and kahweol | Natural coffee diterpenes | 3–6 mg per 150 ml cup in unfiltered coffee (boiled, French press); almost none in paper-filtered coffee | At high doses, cafestol can raise LDL cholesterol |
| Trigonelline | Alkaloid found in the green bean | ≈0.6–1.2% of the green bean; decreases with roasting | As it breaks down, it contributes aroma compounds and forms niacin (vitamin B3) |
| Melanoidins | Polymers formed during roasting through Maillard reactions | Up to ≈25% of the dry matter of roasted coffee | Add colour and body to the drink; researched for their biological properties |
*Values are approximate. They vary widely depending on the species (arabica or robusta), the degree of roast, the brewing method and the cup size.
Not all coffees are chemically the same
A coffee's composition can be shaped long before it ever reaches a roaster. The species, the plant's genetics, where it is grown, environmental conditions, how ripe the fruit is, processing, drying, storage and, later on, roasting and brewing all play a part.
Cafestol offers a particularly curious example.
What is cafestol and how is it related to cholesterol?
Cafestol is a diterpene naturally present in coffee. Its nutritional interest lies mainly in the fact that it can raise LDL cholesterol when exposure is high enough.
And here, quantity matters.
In a randomised clinical trial, 22 people drank five to six cups of French press coffee a day for six months (0.9 litres a day), while another 24 drank filtered coffee.
The French press coffee raised LDL cholesterol by approximately 9–14% compared with filtered coffee during the study. The changes were reversible once the intervention stopped.
This finding needs to be read carefully: the study assessed a high dose. And with more moderate amounts? A more recent clinical trial gave 40 people 12 mg of cafestol a day for 12 weeks, roughly what four 150 ml cups of French press coffee provide. Compared with the placebo group, no statistically significant differences were seen in LDL cholesterol or total cholesterol. It's a small, short study, but it fits with what the body of evidence shows as a whole: cafestol's effect depends on the dose, and relevant increases in cholesterol have been seen with high intakes of unfiltered coffee.
The amount of cafestol can also vary with the coffee itself
A study published in Scientific Reports analysed 107 accessions of Coffea arabica, including cultivars and wild genotypes.
The cafestol content of the green coffee ranged from approximately 300 to 1,300 mg per 100 grams of dry matter. That's more than a fourfold difference between the extremes studied.
It's a fantastic fact for understanding how complex coffee is. Our exposure to cafestol doesn't depend only on asking ourselves "How many coffees do I drink?" We also need to ask, "Which coffee am I drinking?" And there's still one more variable.
Does the brewing method change coffee's compounds?
Yes. The brewing method changes how much of certain compounds present in the coffee ends up in the drink.
Cafestol is a good example once again. Diterpenes are associated with coffee's lipid fraction and can also be found in fine particles. When we use certain filtration systems, especially paper, a very significant share is retained and the concentration that reaches the drink falls considerably.
But that doesn't make one method "good" and another "bad". It simply teaches us something important: the brewing method is another of the variables that determine the final composition of our cup.
And all it takes is switching to a different compound for the conversation to change again.
Coffee isn't just cafestol. It isn't just caffeine either
Two people can say they've had "two coffees" and have taken in different amounts of caffeine. The final concentration depends on many variables: the coffee used, the dose, the grind, the volume of the drink, the extraction time or the brewing method, among others.
That's why counting cups isn't always the same as measuring exposure.
And the same happens, in different ways, with other components. Chlorogenic acids change during roasting. Trigonelline is partly transformed. And as Maillard reactions take place, new molecules appear, including melanoidins.
Roasting coffee isn't simply about turning a green bean into a brown one. Roasting is a huge chemical transformation. And it is precisely this transformation that is responsible for much of what makes coffee extraordinary: its aromas, its colour and many of the flavours we find in the cup.
How composition changes with the type of coffee
The first difference lies in the species. Robusta has roughly twice as much caffeine as arabica and more chlorogenic acids, which partly explains its more bitter taste. Arabica has more lipids, sugars and trigonelline, and tends to give a more complex aromatic profile. Then comes the roast, which transforms the bean. A light roast retains more chlorogenic acids and trigonelline. A dark roast breaks down a larger share of these compounds and, in return, generates more melanoidins and more niacin. Caffeine, on the other hand, remains fairly stable.
Finally, the brewing method decides what passes from the bean into the drink. A paper filter retains almost all of the cafestol and kahweol. French press, Turkish and boiled coffee let them through in much larger amounts, and espresso sits somewhere in between. And decaffeination removes almost all of the caffeine, but keeps a good part of the other compounds. If you'd like to understand better why at Incapto we choose coffee beans over ground coffee or capsules, we explain it in this article on why to choose whole-bean coffee.
What beneficial compounds does coffee have?
So far we've devoted quite a lot of space to what's worth keeping an eye on. But it would be unfair to stop there, because coffee also contains compounds that are very interesting for their possible positive effects.
Polyphenols and chlorogenic acids
Chlorogenic acids are the main family of polyphenols in coffee and one of its most studied bioactive compounds. In fact, for many people coffee is one of the main sources of polyphenols and antioxidants in their diet. They are being researched for their antioxidant and anti-inflammatory activity and for their possible role in glucose metabolism and vascular health.
The amount depends on the bean and, above all, on the roast: a medium roast can lose roughly half of the chlorogenic acids present in green coffee. Part of that loss is offset because other compounds with antioxidant activity, such as melanoidins, form during roasting.
To give an idea of their importance: green arabica coffee contains roughly 4 to 8% chlorogenic acids on a dry-matter basis, and robusta even more. A single cup can provide anywhere from a few tens to several hundred milligrams, depending on the coffee, the roast and how it's brewed.
And here's a very curious fact: most of these compounds are not absorbed in the small intestine. In a study that measured what reached the end of the small intestine, around 70% of the chlorogenic acids in a cup of coffee had not been absorbed. But that doesn't mean they're lost: when they reach the colon, the gut microbiota transforms them into smaller molecules that do pass into the bloodstream, and it's likely that much of their possible effect is due precisely to those molecules. That's why each person may make use of them differently, and why the relationship between coffee and our microbiota is being studied so much today.
Trigonelline and caffeine
Trigonelline is the second most abundant alkaloid in green coffee, after caffeine: around 1% of the dry matter in arabica and slightly less in robusta. About half of it breaks down during roasting and, in the process, it contributes to the formation of aroma compounds and niacin, a form of vitamin B3.
It's also a compound that's attracting a lot of interest. A study published in Nature Metabolism in 2024 observed that older people with sarcopenia, the age-related loss of muscle mass and strength, had lower levels of trigonelline in their blood. In animal models, trigonelline increased levels of NAD+, a key molecule for our cells to produce energy, and helped maintain muscle function during ageing. These are preliminary results, but they show that we are still discovering what some of coffee's compounds do.
As for caffeine, the European Food Safety Authority (EFSA) considers that, in healthy adults, consuming up to 400 mg a day, and up to 200 mg in a single dose, does not raise safety concerns. During pregnancy and breastfeeding, the limit is set at 200 mg a day. Within these limits, caffeine is associated with greater attention and alertness.
What do studies in people say?
An umbrella review published in The BMJ in 2017, which brought together more than 200 meta-analyses, concluded that habitual coffee consumption seems more likely to be beneficial than harmful. The largest risk reductions for various health outcomes were seen at around three to four cups a day, including lower all-cause and cardiovascular mortality, and a lower risk of type 2 diabetes and some liver diseases.
Type 2 diabetes is a concrete example. A meta-analysis of 28 prospective studies, with more than a million participants, published in Diabetes Care in 2014, found that each daily cup was associated with a 9% lower risk for caffeinated coffee and a 6% lower risk for decaf. The fact that decaf also shows this association is particularly interesting: it suggests that not everything is explained by caffeine and that other compounds, such as chlorogenic acids, could play a role.
These are mostly observational associations: on their own, they don't prove that coffee is the cause. And the review itself points out exceptions, such as pregnancy. But they help explain why coffee can't be boiled down to just one of its compounds.
What compounds form during roasting?
Hundreds of new compounds form during roasting. Some are highly prized, such as volatile aroma compounds: more than 800 have been identified in roasted coffee, and they are responsible for much of its aroma and flavour. Others, however, are unwanted, which is why it's worth knowing about them, controlling them and studying them.
Among the latter, the best known is acrylamide, a compound that forms when various foods are heated and also during coffee roasting. Its levels can vary depending on the raw material and the process conditions, including the degree of roast.
Furans and other compounds can also appear during thermal processing.
Why does bean quality matter beyond flavour?
When we talk about coffee quality, we usually think of flavour first. But a good selection of raw material also matters for reasons that go beyond the sensory.
One of the clearest examples is defective beans. Not all defects are the same, but some can be linked to problems during cultivation, processing, drying or storage.
Ochratoxin A is a good example. Unlike acrylamide, it doesn't form during roasting: it's a mycotoxin produced by certain fungi, and various studies have linked a significant part of its presence in coffee to certain defective beans and poor post-harvest practices. In a study carried out with coffee from Kenya, unsound beans initially accounted for 95% of the ochratoxin A contamination in the batch analysed.
That's why there's a reason to stand up for something very simple: the quality of the raw material matters. Proper harvesting, bean selection, processing, drying and storage help reduce defects and allow us to control much better what we ultimately roast and drink.
When it comes to what we can control as consumers, we would start by choosing whole-bean coffee, roasted without added sugar, properly selected, processed and stored, and traceable. We explain how to do it in this guide on how to choose good coffee beans.
Quality isn't just about finding better aromas and flavours in the cup. It also starts much earlier: in carefully selecting what we decide to turn into coffee.
So, is coffee good or bad for your health?
This is probably too simple a question for such a complex drink.
As we've seen, epidemiological research has found associations between coffee consumption and various health outcomes, many of them favourable. But much of this evidence is observational: an association doesn't, on its own, prove that coffee is the cause of a particular effect.
And here a very interesting apparent paradox appears. How can coffee consumption be associated in population studies with certain favourable cardiovascular outcomes and, at the same time, contain cafestol, which we know from clinical trials can raise LDL?
Precisely because a cup of coffee isn't a single molecule. We don't drink isolated cafestol. Nor do we drink only caffeine, chlorogenic acids or melanoidins. We drink the whole coffee.
The four questions we should ask about coffee and health
1. Which coffee?
Not all coffees have the same composition. Species and genetics, origin, processing, possible defects, storage and roasting can all change what we ultimately find in the bean and in the drink.
2. How much?
Quantity matters. Drinking two coffees a day isn't the same as drinking five: the higher the consumption, the greater our exposure to certain coffee compounds, such as caffeine or cafestol, may be. What's more, two "cups" don't necessarily represent the same drink or the same dose. A "cup" can be a 30 ml espresso or a 200 ml filter coffee. So rather than counting cups, it's worth looking at the total amount of coffee we drink and how it's prepared.
3. How?
Brewing matters too. The dose, grind, temperature, contact time with the water and filtration system can change the extraction and, therefore, the concentration of certain compounds we end up drinking. A difference in one specific compound doesn't automatically make one brewing method better or worse than another.
4. For whom?
Our response to coffee isn't identical either. Genetics, our sensitivity to caffeine, our habits, the time of day we drink it and our individual context can all influence how we respond to it. For example, during pregnancy it's recommended not to exceed 200 mg of caffeine a day. And anyone who prefers to cut down on caffeine can opt for decaf. In that case, it's also worth checking how it was decaffeinated: some processes use solvents such as methylene chloride, while others, such as water decaffeination, don't use chemical solvents. Ideally, the packaging should state the process.
A bean just a few millimetres long and more than 1,000 compounds
Perhaps, after this whole journey, the most interesting conclusion isn't deciding whether coffee is good or bad.
It's discovering the extraordinary things that something as small as a coffee bean can hide.
A seed barely a few millimetres long holds enormous complexity that begins with the plant's own genetics and keeps changing with where it grows, how we process the fruit, how we store the bean, how we roast it and, finally, how we choose to brew it.
Science needs to isolate its components in order to study them. We, on the other hand, drink the whole coffee.
Every new study helps us understand one more piece of the puzzle. But we shouldn't mistake that piece for the whole puzzle.
And in the end, coffee is also aroma, flavour, pleasure, ritual, conversation and sharing. Knowing more about what's inside our cup should help us do exactly that: choose our coffee better and enjoy the experience even more. If you're still torn between coffee beans and capsules, we explain it in detail in this article on beans vs. capsules.
Because life is too short to drink bad coffee.
Main scientific sources
- Coffee: biochemistry and potential impact on health (Food & Function, 2014)
- Transforming coffee from an empirical beverage to a targeted nutritional intervention (review)
- Comparison of effect of cafetière and filtered coffee: six month randomised controlled trial
- Genome-wide association study: cafestol and kahweol in 107 Coffea arabica accessions (Scientific Reports)
- Ochratoxin A contamination of coffee batches from Kenya and unsound beans
- A comprehensive review of coffee melanoidins (2026)
- Mechanisms of action of coffee bioactive compounds — the coffee paradox
- Coffee consumption and health: umbrella review of meta-analyses (BMJ, 2017)
- Effects of 12-week supplementation with coffee diterpene cafestol: randomized, placebo-controlled trial (Nutrients, 2024)
- Caffeinated and decaffeinated coffee consumption and risk of type 2 diabetes: a systematic review and dose-response meta-analysis (Diabetes Care, 2014)
- Bioavailability of chlorogenic acids following acute ingestion of coffee by humans with an ileostomy (Archives of Biochemistry and Biophysics, 2010)
- Trigonelline is an NAD+ precursor that improves muscle function during ageing and is reduced in human sarcopenia (Nature Metabolism, 2024)
- EFSA Scientific Opinion on the safety of caffeine (2015)
