Danger of aflatoxins

By Prof. Deepal Mathew

Emeritus Professor
Dept. of Biochemistry and Molecular BiologyFaculty of MedicineUniversity of ColomboSLAAS General President – 2015

Aflatoxins were isolated and characterized in 1960s after the turkey x disease. This disease killed more than 100,000 turkeys in Europe. The toxicity wad discovered to be due to peanut meal produced in South America been contaminated with aflatoxins. Turkeys are very sensitive to aflatoxins as cytochrome P₄₅₀ mediated metabolism of aflatoxin B₁ in liver is efficient while glutatathion X- transferase mediated detoxification is deficient.

Aflatoxin is a mycotoxin mainly produced by two fungi Aspergillus flavurs and Aspergillus parasiticus. These fungi grow well under hot humid conditions in decaying vegetables in soil. Fungi produce four major toxic aflatoxins B₁, B₂, G₁ and G₂ which are present in almost all major food crops. Animal metabolism produces aflatoxin M₁ and M₂ from metabolism of aflatoxin B₁ and B₂. These compounds are found in milk including Brest milk

Food crops are contaminated either pre-harvest or post-harvest. In considering pre-harvest contamination, crops commonly affected are maize, cotton seed and peanuts. Post-harvest contamination occurs mainly in coffee, rice and spices. Improper storage under warm and humid conditions leads to contaminations. In coconut when improperly dried copra is stored under humid conditions the fungi grow on the copra and secrete aflatoxins. When coconut oil is produced from contaminated copra aflatoxins will be present in the coconut oil. Organics crops not treated with fungicides are more susceptible for contamination with aflatoxins.

Toxicity

Aflatoxins, specially aflatoxins B₁ (AFB¹) is associated with toxicity and carcinogenicity in human and animal populations. The international agency for research in cancer has classified AFB₁ as a group 1 carcinogenic. The disease aflatoxicosis is coursed by consumption of aflatoxins. Acute aflatoxicosis lead to death while chronic aflatoxicosis results in liver cancer and immune suppression. Aflatoxins are mutagenic in bacteria and can cause birth defects. Children may become stunted although no direct evidence is available to come to a conclusion. Consumption of food containing 1μg/Kg or higher of aflatoxins are likely to cause aflatoxicosis. Consumption over a period of 1 – 3 week of AFB₁ dose of 20 – 120 μg / Kg body weight per day is acutely toxic and potentially lethal. In most animal species LD₅₀ for aflatoxin vary from 0.3 – 18 mg/ Kg body weight. The safe level for aflatoxin is considered to be 20μg / Kg food and for infant food 10μg / Kg.

Production and removal of aflatoxins

Production of aflatoxins by fungi is temperature and moisture depended. At high humanity no AFB₁ is produced below 20⁰C and above 37⁰C. High production is observed at 28⁰C. High temperature and drought conditions favor the growth of aflatoxin producing fungi in food crops. Aflatoxins are decomposed at temperatures from 237-306⁰C. Therefore, pasteurization does not remove aflatoxin in milk. Prof. Samarajeewa and coworkers reported that aflatoxin in coconut oil is decomposed by exposing as a thin layers to solar radiation. However, no work has been carried out to setup a largescale economical aflatoxin removing method.

Biological methods for removal for aflatoxin

In 2009 a biological method was developed in Africa to reduced aflatoxin contamination in maize and ground nuts. They produced aflasafe a mixture of nonaflatoxin producing strains of Aspergillus flavus isolated from soil. Aflasafe is broadcast in the field and prevent colonization by aflatoxin producing Aspergillus strains. It has been reported that there is a 99% reduction of aflatoxin contamination by using aflasafe in maze and groundnut fields.

Outbreaks of Aflatoxins contamination

1974 – Gujarat and Rajasthan: 106 deaths. Maize contaminated with aflatoxins

2003 – Kenya: 120 confirmed deaths. Maize contaminated with aflatoxins

2013 – Many countries of Europe reported contamination of milk with aflatoxins

2014 – Kenya: five brands of maize flour recalled due to contamination with aflatoxins

2021 – USA: contamination with pet food with aflatoxins

2021 – Sri Lanka: contamination of Coconut oil important from Malaysia with aflatoxins

Conclusion

Aflatoxin is present in most foods. It is important to monitor food we consume to establish that the levels of aflatoxin are in the acceptable levels of below 20μg/ Kg of food.