Mycotoxins: Fungal Toxins in Food and Their Health Risks

Every year, invisible fungal toxins contaminate a massive portion of the world’s food supply. These toxins – called mycotoxins – are produced by common molds that grow on crops in the field, during harvest, and in storage. According to the World Health Organization (WHO), mycotoxins can cause effects ranging from acute poisoning to long-term health consequences like immune deficiency and cancer. Understanding what these toxins are, where they come from, and how they affect human health is essential for anyone studying food safety or working in the food industry.

What are mycotoxins? 🔗

Mycotoxins are toxic secondary metabolites produced by certain species of filamentous fungi, commonly referred to as molds. The term “mycotoxin” comes from the Greek word mykes (fungus) and the Latin word toxicum (poison). Unlike primary metabolites that fungi need for basic growth and reproduction, secondary metabolites like mycotoxins are not essential for the organism’s survival. Instead, they are produced under specific environmental conditions – particularly when the fungus is under stress.

What makes mycotoxins especially dangerous is their chemical stability. Standard food processing methods such as cooking, boiling, baking, frying, and pasteurization cannot fully eliminate them. This means that once a food product is contaminated, the toxin is likely to persist all the way to the consumer’s plate. Research published in Toxicology Reports confirms that most mycotoxins are heat-stable and can even produce harmful breakdown products during processing.

Major mold species responsible for mycotoxin production 🔗

Three fungal genera are primarily responsible for producing the mycotoxins found in our food supply: Aspergillus, Fusarium, and Penicillium. Each genus thrives under different environmental conditions and produces distinct types of toxins.

Aspergillus species 🔗

Aspergillus flavus and Aspergillus parasiticus are the most notorious mycotoxin producers. These molds thrive in warm, humid climates and are responsible for producing aflatoxins – among the most potent naturally occurring carcinogens known. The U.S. Food and Drug Administration (FDA) lists crops like peanuts, corn, tree nuts, and rice as the most susceptible to aflatoxin contamination. Another important species, Aspergillus ochraceus, produces ochratoxin A, which commonly contaminates cereals, coffee, and dried fruits.

Fusarium species 🔗

Fusarium molds are major field fungi, meaning they typically infect crops before harvest. They produce several mycotoxins including fumonisins, deoxynivalenol (DON), zearalenone, and T-2 toxin. These toxins are prevalent in cereals such as wheat, barley, oats, and maize. Fusarium contamination is strongly influenced by climate conditions, and climate change is expected to shift the geographic range of these toxigenic species.

Penicillium species 🔗

Penicillium expansum is the primary producer of patulin, a toxin closely associated with rotting apples and apple products. Penicillium citrinum produces citrinin, which often co-occurs with ochratoxin A and primarily affects grains and fermented foods. While Penicillium is well known as the source of life-saving antibiotics, its toxigenic species remain a significant concern in food safety.

Common mycotoxins and the foods they contaminate 🔗

Although researchers have identified several hundred mycotoxins, a handful are responsible for the greatest damage to human health and the global food supply. Here are the most important ones.

Aflatoxins 🔗

Aflatoxins are produced primarily by Aspergillus flavus and Aspergillus parasiticus. The four main types found in food are aflatoxin B1, B2, G1, and G2, while aflatoxin M1 is found in milk from animals that consumed contaminated feed. Aflatoxin B1 is classified as a Group 1 human carcinogen by the International Agency for Research on Cancer (IARC), meaning there is sufficient evidence that it causes cancer in humans.

Foods most commonly contaminated include corn, peanuts, tree nuts (especially Brazil nuts and pistachios), cottonseed, sorghum, rice, and various spices such as chili peppers and turmeric. Aflatoxin contamination is particularly high in tropical and subtropical regions where warm, humid conditions favour Aspergillus growth.

Ochratoxin A (OTA) 🔗

Ochratoxin A is produced by certain Aspergillus and Penicillium species. It is commonly found in cereals (wheat, rye, barley, oats), coffee beans, wine, grapes, dried fruits, and spices. According to global contamination data, ochratoxin A accounts for approximately 20% of the worldwide mycotoxin burden. This toxin is particularly concerning because it can contaminate foods that appear dry and well-preserved, as the producing fungi can grow at relatively low water activity levels.

Patulin 🔗

Patulin is primarily associated with rotting apples and apple-based products such as juice, cider, and applesauce. It is produced by Penicillium expansum, Aspergillus, and Byssochlamys species. One critical point about patulin is that pasteurization does not eliminate it. This is why the quality of raw apples used in juice production is so important – using moldy fruit significantly raises the risk of patulin contamination in the finished product.

Citrinin 🔗

Citrinin is a polyketide mycotoxin produced by several Penicillium, Aspergillus, and Monascus species. It frequently co-occurs with ochratoxin A, and their combined presence can amplify toxic effects. Citrinin has been reported in rice, wheat, barley, oats, cheese, and various fermented foods. Red yeast rice products, used both as food colouring and traditional medicine in parts of Asia, have been found to be particularly susceptible to citrinin contamination.

Health effects of mycotoxin exposure 🔗

Mycotoxins can cause a wide range of health problems in humans, from acute illness to severe chronic conditions. The specific effects depend on the type of mycotoxin, the dose consumed, the duration of exposure, and individual factors like age, nutritional status, and overall health.

Liver toxicity (hepatotoxicity) 🔗

The liver is the primary target organ for aflatoxins. Acute exposure to high doses of aflatoxins can cause aflatoxicosis, a condition characterised by liver damage that can lead to liver failure and death. In 2004, a severe aflatoxicosis outbreak in Kenya resulted in hundreds of cases and over 100 deaths due to consumption of contaminated maize. Chronic, lower-level exposure is strongly linked to hepatocellular carcinoma (liver cancer), especially in individuals who are also infected with hepatitis B virus.

Kidney damage (nephrotoxicity) 🔗

Ochratoxin A and citrinin are known nephrotoxins, meaning they specifically damage kidney tissue. Chronic ochratoxin A exposure has been linked to Balkan endemic nephropathy, a progressive kidney disease found in parts of southeastern Europe. Research indicates that citrinin usually co-occurs with ochratoxin A, and their combined toxicity to the kidneys can be more severe than either toxin alone.

Carcinogenic effects 🔗

Several mycotoxins have been classified by IARC based on their cancer-causing potential. Aflatoxin B1 is a confirmed Group 1 carcinogen. Ochratoxin A and fumonisin B1 are classified as possible human carcinogens (Group 2B). These toxins promote cancer through multiple mechanisms including direct DNA damage, oxidative stress, disruption of the cell cycle, suppression of apoptosis (programmed cell death), and epigenetic modifications.

Immunosuppression 🔗

Many mycotoxins suppress the immune system, making exposed individuals more vulnerable to infections. Aflatoxins, ochratoxin A, and T-2 toxin are all known to impair immune function. This is especially concerning in developing countries where populations face simultaneous challenges of mycotoxin exposure, malnutrition, and infectious diseases.

Other health effects 🔗

Beyond the liver, kidneys, and immune system, mycotoxins can affect multiple organ systems. Zearalenone acts as an endocrine disruptor and can interfere with reproductive functions. Patulin can cause gastrointestinal disturbances, including nausea and vomiting, and may damage DNA in certain cells. Deoxynivalenol (commonly called “vomitoxin”) causes acute gastrointestinal distress. Some mycotoxins have also been linked to developmental delays in infants and children, particularly in populations with chronic exposure.

Why mycotoxins survive food processing 🔗

One of the most challenging aspects of mycotoxin contamination is the remarkable thermal and chemical stability of these compounds. Unlike bacteria, which can be killed by proper cooking or pasteurization, mycotoxins persist through most standard food processing techniques. Studies show that cooking, baking, frying, and even pasteurization are insufficient to completely eliminate mycotoxins from contaminated foods.

This stability means that prevention – stopping mycotoxin contamination before it occurs – is far more effective than trying to remove toxins from already-contaminated products. Post-harvest cleaning and processing can reduce mycotoxin levels to some extent (by up to 50% in some cases), but they cannot guarantee complete removal.

Scale of the global problem 🔗

Mycotoxin contamination is not a minor or localised issue. Research estimates that 60-80% of global crops are contaminated with detectable levels of mycotoxins, with about 20% exceeding the European Union’s legal food safety limits. The contamination spans nearly every food category – from cereals and nuts to animal products, fruits, spices, and even infant foods.

The economic impact is significant as well. Contaminated crops face rejection in international markets, reduced yields, and lower product quality. Developing countries in Africa and Asia are disproportionately affected, as their agricultural economies are highly dependent on crop exports that are vulnerable to mycotoxin contamination.

Prevention and control strategies 🔗

Since mycotoxins cannot be easily eliminated after they form, effective management focuses on prevention at every stage of the food supply chain – from the field to the consumer’s table.

Pre-harvest measures 🔗

Good agricultural practices (GAP) are the first line of defence. These include selecting resistant crop varieties, proper land preparation, timely planting and harvesting, effective pest and insect control, and managing irrigation to avoid moisture stress. Biocontrol strategies, such as the use of non-toxigenic strains of Aspergillus flavus to competitively exclude toxin-producing strains, have shown promising results in several countries.

Post-harvest measures 🔗

Proper drying of harvested crops to safe moisture levels is critical. Crops should be stored in clean, dry, well-ventilated environments. Sorting and cleaning can remove visibly damaged or mouldy grains. Technologies like optical sorting and cold plasma treatment are emerging as effective post-harvest interventions. Traditional processing methods such as nixtamalization (alkaline cooking of maize) and fermentation can also reduce certain mycotoxin levels.

Regulatory frameworks and monitoring 🔗

Multiple international bodies have established maximum allowable levels for mycotoxins in food. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) conducts risk assessments that inform the Codex Alimentarius Commission’s international food standards. The U.S. FDA, the European Food Safety Authority (EFSA), and the Food Safety and Standards Authority of India (FSSAI) all set specific regulatory limits for key mycotoxins in various food products.

For example, the Codex Alimentarius sets maximum aflatoxin levels in the range of 0.5 to 15 µg/kg for various nuts, grains, dried figs, and milk. The FDA has established action levels for aflatoxins in food (20 ppb total) and milk (0.5 ppb for aflatoxin M1). Patulin limits in apple juice are generally set at 50 µg/L. Continuous monitoring through laboratory testing using methods like HPLC, ELISA, and LC-MS/MS helps enforce these standards across the food supply chain.

The role of climate change 🔗

Climate change is adding a new layer of complexity to the mycotoxin problem. Rising temperatures, shifting rainfall patterns, and increasing atmospheric CO₂ levels are altering the conditions that favour fungal growth and toxin production. Recent research highlights that climate change is shifting the geographic range of toxigenic fungal species, meaning regions that were previously unaffected may face new contamination risks. This makes strengthened surveillance and adaptive agricultural practices more important than ever.

Key takeaways about mycotoxins 🔗

Mycotoxins are toxic secondary metabolites produced primarily by Aspergillus, Fusarium, and Penicillium molds. The most important mycotoxins from a food safety perspective include aflatoxins, ochratoxin A, patulin, and citrinin. These toxins contaminate a wide variety of foods – cereals, nuts, fruits, spices, dairy products, and more. Their health effects are serious: liver cancer, kidney damage, immunosuppression, reproductive issues, and gastrointestinal problems. Because they are chemically stable and survive standard food processing, prevention through good agricultural practices, proper storage, and rigorous regulatory monitoring remains the most effective approach to controlling mycotoxin contamination.

What do you think? Given that a significant majority of global crops show detectable levels of mycotoxin contamination, how well-prepared do you think your local food safety systems are to handle this challenge? And considering the impact of climate change on fungal growth patterns, what new strategies should be prioritised to protect the food supply in the coming decades?

References

1. https://www.who.int/news-room/fact-sheets/detail/mycotoxins
2. https://pmc.ncbi.nlm.nih.gov/articles/PMC11954124/
3. https://www.fda.gov/food/natural-toxins-food/mycotoxins
4. https://publications.iarc.who.int/Book-And-Report-Series/Iarc-Scientific-Publications/Improving-Public-Health-Through-Mycotoxin-Control-2012
5. https://pmc.ncbi.nlm.nih.gov/articles/PMC11545588/
6. https://www.intechopen.com/chapters/80725
7. https://www.sciencedirect.com/science/article/abs/pii/B9780128042397000482
8. https://www.mdpi.com/2304-8158/9/2/137
9. https://pmc.ncbi.nlm.nih.gov/articles/PMC11898784/
10. https://link.springer.com/article/10.1186/s12302-025-01166-x
11. https://pmc.ncbi.nlm.nih.gov/articles/PMC12599949/