Health Effects of Aflatoxins

Aflatoxins are a family of toxins produced by certain fungi that are found on agricultural crops such as maize, peanuts, cottonseed and tree nuts. Chronic consumption of aflatoxin-contaminated foods is a common problem in both humans and animals worldwide. Aflatoxins may contaminate as much as 25% of the world food supply. 

Aflatoxins are a big problem that day by day turns more important due to their implication in crop production, food quality and human and animal health. Aflatoxins are amongst the most poisonous mycotoxins. They have been shown to be genotoxic, meaning they can damage DNA.  

Mycotoxins

Mycotoxins are naturally occurring toxins produced by certain moulds (fungi) and can be found in food. The moulds grow on a variety of different crops and foodstuffs including cereals, nuts, spices, dried fruits, apples and coffee beans, often under warm and humid conditions. Mycotoxins can cause a variety of adverse health effects and pose a serious health threat to both humans and livestock. 

Mould growth can occur either before harvest or after harvest, during storage, on/in the food itself often under warm, damp and humid conditions. Most mycotoxins are chemically stable and survive food processing.

Aspergillus sp.

The main fungi that produce aflatoxins are Aspergillus flavus and Aspergillus parasiticus, which are abundant in warm and humid regions of the world. Aflatoxin-producing fungi can contaminate crops in the field, at harvest and during storage.

Aspergilluss sp. attacks crops on the field or during storage. Generally, those fungi are most frequent in tropical and subtropical regions where environmental factors characterized by high humidity and temperatures are favorable for their production. Aflatoxins are produced as their secondary metabolites including aflatoxin B1. 

Aflatoxicosis

Traditionally, aflatoxin contamination was not frequent in temperate regions such as the Mediterranean, however, with climate change patterns including elevated temperatures, increased humidity and increased droughts, a shift in fungal attack patterns is expected in such areas in a way that favors Aspergillus sp. infestation and aflatoxin contamination. 

Aflatoxins are readily absorbed from the site of exposure usually through the gastrointestinal tract and respiratory tract into blood stream. 

The diseases caused by exposure to aflatoxins are referred to as “aflatoxicosis” that could be acute or chronic.

The toxic effects exhibited by aflatoxins depend on several factors such as age, gender, intake dosage, exposure duration and nutritional status. Acute aflatoxicosis is prevalent when individuals are exposed to food contaminated with high doses of aflatoxins and its symptoms include abdominal pain, vomiting, diarrhea, pulmonary edema, cerebral edema, anorexia, fatty liver, jaundice, depression and photosensitivity. Acute poisoning is more prevalent in developing countries due to the increased risk of contamination of staple food, lack of food security, absence of aflatoxins awareness and lack of regulatory limits.

Aflatoxins in Animals  

Acute aflatoxicosis presents a risk to animals, as well, due to their exposure to aflatoxins through contaminated feed and the susceptibility varies among different species. Acute aflatoxicosis in animals leads to several complications including decreased weight gain, reduction in egg or milk production, decreased feed conversion and increased vulnerability to infectious diseases.

Aflatoxin B1

Aflatoxin B1 (AFB1) is a mycotoxin produced by the common Aspergillus flavus and Aspergillus parasiticus which are common and widespread in nature. The mycotoxin is found in foodstuffs, including corn, rice, oil seeds, dried fruits and peanuts, that have been improperly stored in hot, humid and unsanitary conditions. It is also found in the milk, meat and eggs of farm animals that feed on aflatoxin-contaminated foods. Approximately 4.5 billion people are at risk of chronic exposure to aflatoxin-contaminated food. AFB1 is considered to be an unavoidable contaminant of food, but nevertheless can be minimized. There are four aflatoxins (aflatoxin B1, B2, G1 and G2) that are known to be carcinogenic to both humans and animals, of which aflatoxin B1 is the most potent hepatotoxic and hepatocarcinogenic agent. AFB1 is well-known to have a range of biological activities, including acute toxicity, teratogenicity, mutagenicity and carcinogenicity. Reports from epidemiological studies have demonstrated that AFB1 is the most hepatocarcinogenic mycotoxin and the main contributor to the high rate of hepatocellular carcinoma.

AFB1 is very common in areas such as Southeast Asia and Sub-Saharan Africa. Individuals continuously exposed to this toxin through contaminated food grains and animal products may develop both acute hepatotoxicity and hepatocellular carcinoma.

Chronic Aflatoxicosis 

Chronic aflatoxicosis is caused by being exposed to low doses of aflatoxins for an extended period and results in immune suppression and cancer. The liver is the primary target organ for aflatoxins and chronic consumption could lead to liver cancer, especially when coupled with hepatitis B and/or C virus since those viruses interact synergistically with aflatoxins causing an increased risk of hepatocellular carcinoma. Many toxicological studies demonstrated the carcinogenicity of aflatoxins in many species including mice, rats, hamsters, monkeys and ducks. Aflatoxins have been demonstrated as mutagenic compounds that can alter DNA leading to changes in chromosomes and mutations in genetic codes. Aflatoxins can also lead to other liver diseases such as cirrhosis and hepatomegaly. 

Children are affected through breast milk and direct consumption of weaning foods. Some experts suspect an association between aflatoxin exposure and child growth stunting. 

Immunity

Chronic exposure to aflatoxins has been shown to affect immunity through decreased antibody production, reduced cell-mediated immunity, and decreased resistance to fungal, bacterial and parasitic secondary infection.

Aflatoxins are also responsible for the suppression of both the humoral and cell-mediated immunity and thus making individuals susceptible to infectious diseases. Aflatoxins are also responsible for the malabsorption of various nutrients thus leading to nutritional deficiencies, impaired immune function, malnutrition and stunted growth and hence the development of kwashiorkor and marasmus in infants. 

Pregnancy

Aflatoxins exposure may also lead to low birth weights since exposure can occur in the uterus through a trans-placental pathway. Impaired child growth can be also caused by being exposed to aflatoxins, especially since exposure is higher in children due to their low body weights which leads to more toxic effects. 

Preventing Aflatoxins in Food

Integrated network collaborations of different sectors, including public health, agricultural departments and mass media are required to ensure effective food regulation systems so as to minimize contamination of food by aflatoxins. By training farmers how to implement locally applicable interventions and increasing awareness of dietary changes and sanitation, prevention methods may be initiated at a local level.

Aflatoxins are relatively stable to heat and are not destroyed by normal food processing practices, such as fermenting, boiling, cooking, baking, pasteurization or autoclaving.

Make sure that foods are stored properly – kept free of insects, dry and not too warm. Do not keep foods for extended periods of time before being used. Avoid damage to grains before and during drying, and in storage, as damaged grain is more prone to invasion of moulds and therefore mycotoxin contamination. 

Inspect whole grains (especially corn, wheat, rice), dried figs and nuts such as peanuts, pistachio, almond, walnut, coconut, Brazil nuts and hazelnuts which are all regularly contaminated with aflatoxins for evidence of mould and discard any that look mouldy, discoloured or shriveled. Buy grains and nuts as fresh as possible. You can reduce your aflatoxin exposure by buying only major commercial brands of nuts and nut butters and by discarding nuts that look moldy, discolored or shriveled.

One very simple step that individuals can take to reduce their exposure to aflatoxin is to diversify their diet, where possible.