Understanding the Harmful Compounds in Coffee

November 18, 2025 •

4 min read

According to the International Agency for Research on Cancer, acrylamide, a byproduct of coffee roasting, is classified as a probable human carcinogen, prompting concerns about the harmful compounds in coffee. However, the level found in a typical cup is minimal, and other factors and compounds also warrant consideration.

Quick Summary

This article details potential health concerns related to coffee consumption, covering naturally occurring compounds like acrylamide and diterpenes, as well as contaminants like mycotoxins and pesticides. It explores how brewing methods influence exposure levels and provides actionable tips for mitigating risks.

Key Points

Acrylamide Reduction: Opt for darker roasts or higher-quality Arabica beans, as they tend to have lower acrylamide content compared to light roasts and Robusta varieties.
Cholesterol Control: Use paper filters to brew your coffee, which effectively removes the cholesterol-raising diterpenes cafestol and kahweol.
Mycotoxin Avoidance: Choose high-quality, specialty-grade coffee and store it properly in a cool, dry place to prevent mold growth.
Pesticide Minimization: Select certified organic coffee beans to ensure they are grown without the use of synthetic pesticides and herbicides.
Moderate Caffeine Intake: Be aware of your caffeine consumption, as excessive amounts can cause side effects like anxiety, high blood pressure, and sleep disturbances in sensitive individuals.
Holistic Health: While some compounds can be harmful in high doses, the overall health benefits of coffee, such as its high antioxidant content, often outweigh the minimal risks associated with moderate consumption.

Coffee is one of the most widely consumed beverages globally, cherished for its rich flavor and energizing effects. While numerous studies highlight coffee's antioxidant and anti-inflammatory benefits, others point to the presence of certain compounds that can be harmful, especially in excess or when coffee is improperly prepared or sourced. Understanding these components is key to making informed choices for a healthier coffee habit.

Unpacking the Compounds Formed During Processing

Acrylamide

Acrylamide is a chemical that naturally forms in many foods, including roasted coffee beans, during high-temperature cooking methods like roasting. It is a result of the Maillard reaction, which is responsible for the beloved browning and flavor of coffee. While the International Agency for Research on Cancer classifies acrylamide as a 'probable human carcinogen' based on animal studies, the levels in brewed coffee are significantly lower than the amounts shown to cause harm in animals.

The amount of acrylamide can vary significantly based on roasting time and bean type. Some studies suggest that darker roasts may contain less acrylamide than lighter roasts because the compound breaks down over a longer heating period. Additionally, Arabica beans typically contain less acrylamide than Robusta beans.

Diterpenes (Cafestol and Kahweol)

Cafestol and kahweol are naturally occurring oily compounds found in coffee beans that have been linked to an increase in LDL ('bad') cholesterol levels. These diterpenes are a concern for individuals with high cholesterol or those at risk for heart disease. The key takeaway is that the presence of these compounds is largely determined by the brewing method.

Filtered coffee, such as that made with a drip machine or pour-over using a paper filter, removes nearly all the diterpenes. Conversely, unfiltered methods like French press, espresso, and Turkish coffee allow these compounds to pass directly into the final brew. Therefore, for those monitoring cholesterol, the brewing technique is a critical consideration.

External Contaminants and How to Avoid Them

Mycotoxins

Mycotoxins, such as ochratoxin A (OTA) and aflatoxin, are toxic compounds produced by molds and fungi that can grow on crops like coffee beans, particularly during improper drying, storage, or transport in hot and humid conditions. Poor-quality, conventionally-grown beans are more susceptible to contamination.

The good news is that high-quality, specialty-grade coffee and the roasting process itself significantly mitigate this risk. Roasting effectively destroys 70-90% of mycotoxins. Regulatory standards also ensure that commercial coffee products remain well below safety limits. Consumers can minimize exposure by opting for reputable, organic, and well-processed coffee.

Pesticides and Herbicides

Conventional coffee agriculture often relies on a range of pesticides and herbicides, some of which are classified as probable carcinogens. Glyphosate is a commonly cited example, used to control weeds on large-scale farms. While roasting can remove some of these chemicals, residues can remain. Organic coffee, which is grown without synthetic pesticides or herbicides, is the best option for avoiding these residues.

Heavy Metals

Trace amounts of heavy metals like lead and cadmium can naturally occur in the environment and be absorbed by coffee plants. These levels are generally extremely low and within safe limits set by regulatory bodies. However, improper agricultural practices or contamination from industrial runoff can increase these levels. High-quality, ethically-sourced coffee is less likely to contain elevated levels of heavy metals.

Comparison Table: Filtered vs. Unfiltered Coffee


Feature	Filtered Coffee (e.g., Drip, Pour-Over)	Unfiltered Coffee (e.g., French Press, Espresso)
Effect on Cholesterol	Lowers risk due to removal of cafestol and kahweol.	Higher risk due to retention of cholesterol-raising diterpenes.
Diterpene Content	Very low to negligible.	Significantly higher.
Acrylamide Content	Varies, but influenced more by roast level.	Varies, but concentration can be high depending on preparation.
Body and Mouthfeel	Cleaner, lighter body.	Richer, heavier body with more oil.
Taste Profile	Brighter, cleaner flavor notes.	More intense, full-bodied flavor.

How to Reduce Harmful Compounds in Your Coffee

To enjoy your coffee with greater peace of mind, consider these strategies:

Choose Certified Organic Beans: Opt for organic coffee to avoid synthetic pesticides and herbicides.
Buy High-Quality, Specialty-Grade Coffee: Higher-grade beans are processed and stored with greater care, which minimizes the risk of mycotoxin contamination.
Select Darker Roasts: Some research suggests darker roasts contain lower levels of acrylamide than medium roasts.
Use a Paper Filter: This is the most effective method for removing the cholesterol-raising diterpenes like cafestol and kahweol.
Store Properly: Keep your coffee beans in a cool, dry place to prevent mold growth and the formation of mycotoxins.
Brew Wisely: For filtered methods, shorter brew times and lower water temperatures can minimize acrylamide extraction.

Conclusion: A Balanced Perspective on Coffee

While the presence of harmful compounds like acrylamide, mycotoxins, and diterpenes is a valid concern, it is crucial to maintain perspective. The concentration of these compounds in most high-quality, properly prepared coffee is very low and unlikely to pose a significant health risk for moderate consumers. Many studies even suggest that the overall health benefits of coffee, particularly from its antioxidants and other beneficial compounds, outweigh the risks. By being mindful of your coffee's source and preparation method, you can minimize potential risks and continue to enjoy your daily cup as part of a healthy lifestyle. For more information on the beneficial aspects of coffee, visit Coffee and Health.

Moderation and mindful consumption are the ultimate strategies for enjoying coffee responsibly. The choice between filtered and unfiltered, light and dark, or organic and conventional beans offers control over your exposure to specific compounds, allowing you to tailor your coffee habit to your personal health needs.

Frequently Asked Questions

Yes, all coffee made from roasted beans contains small amounts of acrylamide, which forms during the high-temperature roasting process via the Maillard reaction. However, the levels are typically very low, and some factors like roast time and bean type can influence the final amount.

To avoid cafestol and kahweol, the cholesterol-raising diterpenes in coffee, use filtered brewing methods such as a drip machine, pour-over, or Chemex with a paper filter, which effectively traps these oily compounds.

Yes, certified organic coffee is grown without synthetic pesticides and herbicides, which can reduce your exposure to those chemicals. High-quality organic coffee is also less prone to mycotoxin contamination due to better processing and storage practices.

For high-quality, commercially available coffee, mycotoxins are not a major concern. Stringent quality controls and the roasting process itself remove or significantly reduce mycotoxin levels to well below safety limits.

Filtered methods like pour-over or drip coffee are considered the safest for minimizing exposure to cholesterol-raising compounds. However, the 'safest' method overall depends on which specific compound you are most concerned about.

It depends. Dark roasts may contain lower levels of acrylamide, as the compound breaks down over a longer roasting time. However, some other compounds, like polycyclic aromatic hydrocarbons (PAHs), might increase in dark roasts. The best choice is often a matter of balancing different factors.

While caffeine is safe in moderation for most people, excessive intake can lead to side effects such as insomnia, nervousness, anxiety, restlessness, and increased heart rate. It can also temporarily raise blood pressure in sensitive individuals.

Decaf coffee still undergoes the roasting process, so it still contains acrylamide. Some studies even show decaf may have higher mycotoxin levels, as caffeine inhibits mold growth. However, the decaffeination process itself, if done with solvents, could introduce trace chemicals, so choosing a Swiss Water Process decaf is recommended.