Why toxicologists aren't losing sleep over coffee?

One of the occupational hazards of working in the coffee world is that many people start treating you like a barista, chemist, and doctor all at the same time. Someone will ask if darker coffees contain more caffeine. Another will bring up acidity. And, sooner or later, someone will lower their voice and ask:

—"What about acrylamides?"

That moment arrived during a course I was recently teaching. Suddenly, the room was filled with weekend toxicologists, wondering if their daily coffee ritual had been silently conspiring against them all these years.

My answer was immediate: "The dose makes the poison." It's an old phrase, borrowed from 16th-century medicine, that usually deflates the most dramatic food scares. But when the class ended, I realized that the students had stumbled upon a genuinely fascinating question, one that sits at the crossroads of chemistry, roasting, and the strange ways we think about risk.

Because acrylamide isn't really a story about coffee. It's a story about how a single molecule can shape our perception of an entire food.

The Molecule Nobody Asked For

Roasting coffee is an exercise in controlled chaos. Within a matter of minutes, a dense, grassy seed is transformed by heat into a roasted bean laden with compounds that will eventually give rise to one of the most chemically complex beverages on the planet.

Thousands of compounds are created along the way. Sugars caramelize, acids break down, proteins rearrange, and the Maillard reaction—the same process responsible for the aroma of freshly baked bread and roasted meat—generates many of the flavors we associate with coffee. Acrylamide is one of those compounds.

Food scientists first drew attention to it in 2002, when researchers discovered that starchy foods cooked at high temperatures could contain measurable amounts of a molecule that lab studies had linked to cancer in animals. Overnight, coffee found itself on an unexpected list alongside potato chips, toast, and French fries.

The concern was understandable. Acrylamide is classified by the International Agency for Research on Cancer as a probable carcinogen. That label often brings conversations to a screeching halt.

But labels, as it turns out, rarely tell the whole story.

The Roasting Paradox

Most people assume that darker coffee contains more acrylamide. After all, if roasting creates the molecule, shouldn't a longer roast create even more?

Surprisingly, no.

Studies tracking acrylamide formation during roasting have revealed something far more interesting: the compound follows a bell-shaped curve. It appears when beans reach high temperatures, peaks around a medium roast, and then begins to disappear as roasting continues.

The same heat responsible for creating acrylamide ends up destroying some of it.

In practical terms, this means darker coffees often contain less acrylamide than light or medium roasts. The relationship isn't perfectly linear—coffee variety, roast profile, and industrial practices all matter—but popular intuition gets the chemistry backward. Coffee, once again, refuses to be simple. (Our coffee world mantra continues: it depends...)

Not All Coffees Are Created Equal

The story gets even more complicated when we look beyond the roasting drum.

Different coffee species begin the process with varying chemical compositions. Coffea canephora, more commonly known as Robusta, contains significantly more amino acids involved in acrylamide formation than Coffea arabica. Since many commercial blends rely heavily on Robusta, they often start with a higher potential to generate the compound.

This is one reason why specialty coffee often fares slightly better in lab analyses.

Research comparing specialty and commercial coffees has found that industrial blends can contain about 25–30% more acrylamide than their specialty counterparts. Part of that difference comes from species selection, but processing decisions also play a role. Large-scale manufacturers often prefer faster roasting styles and water quenching systems, whereas specialty roasters generally rely on gentler roast profiles and air cooling.

This doesn't mean that specialty coffee is "clean" and commercial coffee is "contaminated." Coffee is chemistry, regardless of price. But it does remind us that decisions made long before brewing can shape the compounds that end up in the cup.

The Dose Problem

At this point, many readers will be asking the same question as my students:

Should I really be worried?

To answer that, we need to leave chemistry behind and delve into the world of toxicology.

One of the most comprehensive studies on acrylamide in coffee, conducted by Polish researcher Hanna Mojska and her team, found average concentrations of approximately 180 micrograms per kilogram in roasted coffee and about twice that in instant coffee.

Those numbers sound intimidating until we remember one detail: nobody eats whole coffee. Or, to be more precise, nobody except a handful of coffee folks who have somehow convinced themselves that eating roasted beans is normal behavior.

Once diluted in a cup, the picture changes dramatically.

A cup of coffee (180ml) contains about one microgram of acrylamide, sometimes less, sometimes a little more depending on how it's prepared. In comparison, a single serving of french fries can contain tens of times more. Toast, cereals, and other common dietary items can also contribute substantially larger amounts.

This is where Paracelsus's famous saying becomes relevant again.

The dose makes the poison.

The mere presence of a compound tells us surprisingly little about its actual risk.

The Epidemiological Mystery

And now we come to the strangest part of the story.

Coffee contains a compound classified as a probable carcinogen. In theory, acrylamide can be converted in the liver into molecules capable of damaging DNA. On paper, that sounds deeply concerning.

However, decades of research on actual coffee drinkers tell a very different story.

Large epidemiological studies involving hundreds of thousands of people consistently fail to find an increased risk of cancer associated with coffee consumption. In fact, many studies report the exact opposite: regular coffee drinkers tend to have lower rates of liver disease, type 2 diabetes, and premature death.

In 2017, an umbrella review led by Robin Poole analyzed over 200 meta-analyses and concluded that drinking three to four cups of coffee a day was associated with the greatest reduction in overall mortality.

How can both be true?

The answer is that coffee is not acrylamide.

Coffee is an astonishingly complex mixture of hundreds of compounds that interact with each other and with our own biology. Researchers suspect that molecules like cafestol, kahweol, and various antioxidants may help activate the body's detoxification systems, although the details are still being uncovered.

What we can confidently assert is that isolating a single molecule rarely tells the whole story of a food.

Coffee Science Enters the Biotech Age

Acrylamide may not pose a major public health crisis, but that hasn't stopped the food industry from trying to reduce it.

Manufacturers of instant coffee, in particular, have invested heavily in mitigation strategies because instant coffee tends to concentrate acrylamide during processing.

One of the most fascinating developments came this year when European regulators approved the use of Acrylerase®, an enzyme specifically designed to break down acrylamide before coffee extracts are dried into powder.

The enzyme doesn't change the taste of the coffee or alter its aroma. It simply dismantles the molecule itself, reducing acrylamide concentrations by up to 90%.

It's a reminder that coffee science isn't just limited to farms and roasteries. Increasingly, it also lives in bioreactors, research labs, and regulatory agencies.

A Lesson in Perspective

The internet has an extraordinary talent for turning infinitesimal amounts of chemistry into existential threats.

Acrylamide is real, and scientists are right to study it carefully. The molecule deserves scrutiny, and the coffee industry has good reason to continue reducing its presence wherever possible.

But the broader lesson has less to do with coffee and more to do with how we think.

We tend to fear compounds we can name and ignore risks we encounter every day. We hear the words *probable carcinogen* and imagine a catastrophe, even when the quantities involved are minuscule and the epidemiological evidence points in the opposite direction.

There, in our classroom, my students asked exactly the right question. However, the answer wasn't hidden in a chromatograph or a toxicology textbook. It was hidden in a principle that has survived for almost five centuries:

The dose makes the poison.

And in the case of coffee, context matters even more.



Referencias y lecturas sugeridas

References and further reading

• Bagdonaite, K., Derler, K., & Murkovic, M. (2008). Determination of acrylamide during roasting of coffee. Journal of Agricultural and Food Chemistry, 56(15), 6081–6086. https://doi.org/10.1021/jf073051p
  
  

• Cavin, C., Holzhaeuser, D., Scharf, G., Constable, A., Huber, W. W., & Schilter, B. (2002). Cafestol and kahweol, two coffee specific diterpenes with anticarcinogenic activity. Food and Chemical Toxicology, 40(8), 1155–1163. https://doi.org/10.1016/s0278-6915(02)00029-7
  
  

• Ding, M., Satija, A., Bhupathiraju, S. N., Hu, Y., Sun, Q., Han, J., Lopez-Garcia, E., Willett, W., van Dam, R. M., & Hu, F. B. (2015). Association of coffee consumption with total and cause-specific mortality in 3 large prospective cohorts. Circulation, 132(24), 2305–2315. https://doi.org/10.1161/circulationaha.115.017341
  
  

• Duale, N., Bjellaas, T., Alexander, J., Becher, G., Haugen, M., Paulsen, J. E., Frandsen, H., Olesen, P. T., & Brunborg, G. (2009). Biomarkers of human exposure to acrylamide and relation to polymorphisms in metabolizing genes. Toxicological Sciences, 108(1), 90–99. https://doi.org/10.1093/toxsci/kfn269
   

• Esposito, F., Fasano, E., De Vivo, A., Velotto, S., Sarghini, F., & Cirillo, T. (2020). Processing effects on acrylamide content in roasted coffee production. Food Chemistry, 319, 126550. https://doi.org/10.1016/j.foodchem.2020.126550
  
  

• Farah, A. (2012). Coffee constituents. Coffee: Emerging Health Effects and Disease Prevention, 21–58. https://doi.org/10.1002/9781119949893.ch2
  
  

• Freedman, N. D., Park, Y., Abnet, C. C., Hollenbeck, A. R., & Sinha, R. (2012). Association of coffee drinking with total and cause-specific mortality. New England Journal of Medicine, 366(20), 1891–1904. https://doi.org/10.1056/nejmoa1112010
  
  

• Mojska, H., Gielecińska, I., Szponar, L., & Ołtarzewski, M. (2010). Estimation of the dietary acrylamide exposure of the Polish population. Food and Chemical Toxicology, 48(8–9), 2090–2096. https://doi.org/10.1016/j.fct.2010.05.009
  
  

• Poole, R., Kennedy, O. J., Roderick, P., Fallowfield, J. A., Hayes, P. C., & Parkes, J. (2017). Coffee consumption and health: Umbrella review of meta-analyses of multiple health outcomes. BMJ, j5024. https://doi.org/10.1136/bmj.j5024
  
  

• Stadler, R. H., Blank, I., Varga, N., Robert, F., Hau, J., Guy, P. A., Robert, M.-C., & Riediker, S. (2002). Acrylamide from Maillard reaction products. Nature, 419(6906), 449–450. https://doi.org/10.1038/419449a
  
  

• Zorn, H., Barat Baviera, J. M., Bolognesi, C., Catania, F., Gadermaier, G., Greiner, R., Mayo, B., Mortensen, A., Roos, Y. H., Solano, M. L. M., Van Loveren, H., Vernis, L., Fernàndez‐Fraguas, C., Cavanna, D., Criado, A., Lunardi, S., & Liu, Y. (2026). Safety evaluation of the food enzyme amidase from the genetically modified Escherichia coli strain SP‐a. EFSA Journal, 24(5). https://doi.org/10.2903/j.efsa.2026.10089