What is aflatoxin?
Aflatoxins (AFT) are a group of chemically similar metabolites produced primarily by Aspergillus flavus, Aspergillus parasiticus, and have the highest occurrence in food and feed in hot and humid regions.
They are found in soil, plants and animals, and various nuts, and are particularly likely to contaminate peanuts, corn, rice, soybeans, wheat, and other food and oil products, and are among the most toxic of mycotoxins, with a significant risk to human health.
Carcinogenicity of aflatoxin
Aflatoxin is classified as a Class 1 carcinogen by the World Health Organization and remains most abundant in the human liver and causes the most damage to the liver.
A number of research studies have shown that aflatoxin may be an independent risk factor for the development of liver cancer.
- aflatoxin B1 (AFB1) has been shown to induce hepatocellular carcinoma in experimental animals;
- A positive association between aflatoxin B1 intake in the population (consumption of moldy corn or peanuts) and mortality from liver cancer was found;
- The mortality curve of liver cancer is consistent with the regional temperature and humidity curve, indirectly supporting the aflatoxin theory;
- Investigation of the relationship between food and liver cancer morbidity and mortality suggests that consumption of corn, peanuts, and peanut oil is associated with it, whereas consumption of rice, vegetables, protein, and fiber is not.
Where is aflatoxin found?
Aflatoxins are mainly B1, B2, G1, G2 and two other metabolites, M1 and M2. Aflatoxin B1 is the most carcinogenic and is mainly found in moldy peanuts, walnuts, corn and peanut oil containing oil or starch, but also in soybeans, rice, macaroni and spices. Aflatoxin M1 is mainly found in milk and dairy products.
Hot and humid environments are conducive to the growth of Aspergillus flavus and the production of aflatoxin, which can sometimes reach dangerous levels before the appearance of mold visible to the naked eye.
China’s National Standard for Food Safety Limits for Mycotoxins in Food (GB 2761-2017) stipulates that aflatoxin B1 in foods such as corn, peanuts and peanut oil should not exceed 20 μg/kg, and the limit for aflatoxin M1 in milk and dairy products should not exceed 0.5 μg/kg.
How to avoid the harmful effects of aflatoxin?
Aflatoxin is very “stubborn” and difficult to degrade or remove.
- Insoluble in water and cannot be removed by water washing;
- Very resistant to high temperatures, 268°C to be destroyed, the temperature at which food is normally cooked and processed cannot degrade aflatoxin;
- Aflatoxin and hepatitis virus infection also have a superimposed effect on liver damage.
The effects of aflatoxin can be avoided by:
- Discard moldy foods. Moldy peanuts or corn should always be thrown away and should not be given to animals. Try to eat peanuts or corn that has been dried promptly after harvest and is well preserved.
- Eat regular oils. Oil from informal sources, such as oil presses, can carry residue, which has high levels of aflatoxin. In the case of formal peanut oil, the “crude oil” is refined in several steps to bring the aflatoxin content down to the standard range.
- Clean your dishes regularly. Wooden and bamboo chopsticks are susceptible to mold and aflatoxin after 6 months of use, so pay attention to whether there are moldy spots, discoloration and odor when using them, wash and dry them after use, and be careful to replace them with new ones.
Aflatoxin-induced liver cancer is a long-term, chronic process, and occasional ingestion of foods with excessive aflatoxin levels is not a cause for undue concern, but it is important to avoid long-term ingestion of excess aflatoxin, which can accumulate in the body to produce chronic toxicity and carcinogenic effects.