Despite having a poor reputation in the past, coffee actually has many health benefits. Yet, there has been talk of potentially harmful chemicals called mycotoxins in coffee.
Some people claim that a lot of the coffee on the market contains these toxins, increasing your risk of disease.
This article reviews mycotoxins in coffee and explains whether you should be concerned about them.
Mycotoxins are, as the name suggests, toxins formed by molds — tiny fungi that may grow on crops like grains and coffee beans if they’re improperly stored (1).
These toxins can cause poisoning when you ingest too much of them (
They may also cause chronic health concerns. In fact, mycotoxins are what cause indoor mold contamination, which can happen in old, damp, and poorly ventilated buildings (
Some chemicals produced by molds may affect your health, while some have been used as pharmaceutical drugs. These include the antibiotic penicillin, as well as ergotamine, an anti-migraine drug that can also be used to synthesize the hallucinogen LSD.
So, many different types of mycotoxins exist. The ones most relevant to coffee crops are aflatoxin B1 and ochratoxin A.
Aflatoxin B1 is a known carcinogen and has been shown to have various harmful effects. Ochratoxin A has been less studied, but it’s believed to be a weak carcinogen that may be harmful to your kidneys (
Still, it’s important to keep in mind that you are regularly exposed to trace amounts of harmful substances, including mycotoxins. What’s more, your liver can neutralize mycotoxins, which means they do not build up in your body as long as your exposure remains low.
Plus, at least 100 countries around the world regulate the levels of these compounds, though some have stricter standards than others (4).
Mycotoxins are toxic chemicals produced by molds — tiny fungi that are found in the environment. Molds and mycotoxins may occur in crops like grains and coffee beans.
Several studies have found measurable levels of mycotoxins in coffee beans — both roasted and unroasted — as well as brewed coffee:
- Of samples of green coffee beans from Brazil, 33% had low levels of ochratoxin A (5,
- Of coffee brews from commercially available coffee beans in Portugal, 18% contained ochratoxin A (7).
- Aflatoxins have been found in green coffee beans, the highest level in decaffeinated beans. Roasting reduced the levels by 42–55% (
- Though 27% of roast coffees contained ochratoxin A, much higher amounts were found in chili (
Evidence shows that mycotoxins are present in a large percentage of coffee beans and make it into the final drink. That said, a 2021 study found that there was no historical evidence to be able to say that ochratoxin A is acutely toxic if consumed from coffee or other sources (
Plus, their levels are far below the safety limit.
Understandably, you may still not like the idea of having toxins in your foods or beverages. But keep in mind that toxins — including mycotoxins — are everywhere, making it is impossible to avoid them completely.
According to one study, almost all types of foods can have mycotoxins, and virtually everyone’s blood may test positive for ochratoxin A. It has also been found in human breast milk (11,
Various other foods and beverages contain measurable — but acceptable — levels of mycotoxins as well, such as grains, raisins, beer, wine, cereal, dark chocolate, and peanut butter (
This means that though you may be ingesting and inhaling various toxins each day, you should not be affected if their amounts are small.
Claims that mycotoxins are responsible for coffee’s bitter taste are also incorrect. The amount of tannins in coffee determines its bitterness. Evidence to suggest that mycotoxins have anything to do with it is lacking.
Purchasing high quality products — whether coffee or other foods — is generally a good idea, but paying extra for mycotoxin-free coffee beans is most likely a waste of money.
Trace amounts of mycotoxins have been found in coffee beans, but the amounts are far below safety limits and too low to be of practical significance.
Molds and mycotoxins in foods are nothing new. They’re well-known concerns, and coffee growers have found efficient ways to deal with them.
The most important method is called wet processing, which effectively gets rid of most of the molds and mycotoxins (16).
Roasting the beans also kills the molds that produce the mycotoxins. According to one older study, roasting can reduce ochratoxin A levels by 69–96% (
Coffee’s quality is rated according to a grading system, and the presence of molds or mycotoxins significantly lowers this score. What’s more, crops get discarded if they exceed a certain level.
Even lower-quality coffees have levels well below the safety limits set by regulatory authorities and significantly below the levels shown to cause harm.
In a Spanish study, the total ochratoxin A exposure in adults was estimated to be only 3% of the maximum level regarded as safe by the European Food Safety Authority (
Another older study showed that 4 cups of coffee daily provide only 2% of the ochratoxin A exposure deemed safe by the Food and Agriculture Organization and the World Health Organization (19).
Decaf coffee tends to be higher in mycotoxins. This is because caffeine, which is removed from decaf coffee, helps stop the growth of molds. Instant coffee also contains higher levels than regular coffee, but they are still too low to be of concern (
Coffee makers are well aware of mycotoxin concerns and use methods like wet processing to significantly reduce levels of these compounds.
Mycotoxins are found in small amounts in various foods, including coffee.
However, their levels should be strictly monitored by producers and food safety authorities. When levels go above safety limits, the food products are recalled or discarded.
Research shows that the benefits of coffee still far outweigh the potential negatives. What’s more, there’s no evidence to suggest that low levels of mycotoxin exposure are harmful.
Still, if you want to minimize your risk, only drink quality caffeinated coffee and store it in a dry, cold place.
If you are concerned about nutrition and health benefits, you may also want to avoid adding sugar or heavy creamers. This will help keep your coffee healthy.