Aflatoxins in food: Overview, meaning and scientific definitions

Overview

The word aflatoxin is a relatively new term, as far as the history of named diseases go. It was first used in the UK in the 1960’s, after the outbreak of an unidentifiable disease on a turkey farm. The term was used to define a toxic component found in ground meal from Brazil, which had been fed to the turkeys leading to the outbreak of the disease. [1]

Aflatoxins are part of a wider group of fungal toxins knowns as mycotoxins, of which there is estimated to be around 450 different types globally, with aflatoxins being some of the most toxic and dangerous to humans and animals. Aflatoxin is a common name for specific secondary metabolites produced by Aspergillus fungi, primarily Aspergillus flavus, Aspergillus parasiticus and Aspergillus nomius. These types of aflatoxigenic fungi produce various members of the aflatoxin group of chemicals- AFB_1,AFB_2,AFG₁ and AFG_2.[2]

Exposure to aflatoxins through diet can lead to serious health complications and consequences. The effects can be both acute and long term, and their effects on the human body vary; they can be teratogenic, mutagenic, carcinogenic, immunotoxic and hepatotoxic to humans. Aflatoxins predominately affect the liver and kidneys, but can also affect reproductive organs. [3]

Many foods can become contaminated by aflatoxins, during the growing and harvesting process of many agricultural foods. Crops predominantly affected during pre-harvest contamination of aflatoxins are maize, cottonseed, peanuts and tree nuts. Contamination after harvest usually occurs in crops such as coffee beans, rice and spices. Crops and foods are more susceptible to aflatoxin contamination in humid and warmer climates or storage environments. [4]

Contaminated crops can also have an impact on animal feed, which often contains corn and/or cereals, which can subsequently lead to the contamination of animal food products and even dairy products. Ingestion of aflatoxin contaminated feeds by dairy cows can be absorbed and metabolised in the rumen’s digestive tract by microorganisms of the ruminal flora and excreted as aflatoxicol in either the urine or milk. Studies have shown that even pasteurisation of milk does not alter the carry over levels of aflatoxicol in milk and dairy products from cows which have been fed contaminated feed. [5]

FSTA Dictionary [6] definitions of various Aflatoxins:

Aflatoxins: Mycotoxins produced by certain strains of Aspergillus, most notably flavus and A. parasiticus. Formed during growth of these fungi on commodities such as cereals (e.g. corn), nuts (e.g. peanuts) and oilseeds (e.g. soybeans). Contamination can take place both pre- and post-harvest. Host crops are particularly susceptible to infection following prolonged exposure to high humidities or damage during drought conditions. Once ingested, aflatoxins are metabolized by the liver to a reactive intermediate, aflatoxin M1. Hepatotoxic and hepatocarcinogenic in humans and animals, and can result in aflatoxicosis.
Aflatoxin B1: Potent hepatotoxic, hepatocarcinogenic, mutagenic and teratogenic mycotoxins produced by Aspergillus flavus and parasiticus. Formed during growth on a wide range of crops, including peanuts, corn and other cereals, and oilseeds. Metabolized to aflatoxin M1 and aflatoxin Q1.

Peanuts | IFIS Publishing

Aflatoxin B2: Moderately potent hepatotoxic, hepatocarcinogenic, mutagenic and teratogenic mycotoxins produced by Aspergillus flavus and parasiticus. Dihydroxy derivatives of aflatoxin B1. Formed during growth on the same commodities as aflatoxin B1 (including peanuts, corn and other cereals, and oilseeds), but in smaller amounts. Metabolized to aflatoxin M2, and excreted in milk in this form.

Aflatoxin B3: Toxic mycotoxins produced by older cultures of Aspergillus parasiticus and flavus. Alternative name for parasiticol.

Aflatoxin D1: Carboxylated product of aflatoxin B1, produced by the reaction between aflatoxin B1 and heated ammonium hydroxide. Possesses lower toxicity than aflatoxin B1.

Aflatoxin G1: Potent carcinogenic and genotoxic mycotoxins produced by Aspergillus parasiticus and other Aspergillus species. Formed during growth on a wide range of crops, including peanuts, corn and other cereals, and oilseeds. Possess toxicity and structure similar to those of aflatoxin B1.

Aflatoxin G2: Mildly carcinogenic and genotoxic mycotoxins produced by Aspergillus parasiticus and other Aspergillus species. Occur in a wide range of foods, including nuts, seeds, beans, spices and fruits. Dihydroxy derivative of aflatoxin G1, with lower toxicity.

Aflatoxin M1: The toxic, 4-hydroxy derivative of aflatoxin B1, found in the livers, kidneys, blood, faeces, urine and milk of mammals that have consumed aflatoxin B1 contaminated feeds or foods. Subsequently occurs in dairy products, particularly cheese, and human milk. Produced in small quantities by Aspergillus flavus and parasiticus, and can occur in corn, nuts and soybeans. Associated with liver damage and cancer. Possesses lower toxicity than aflatoxin B1. Aflatoxin M1 can be degraded by UV radiation.

Aflatoxin M2: The toxic, 4-hydroxy derivative of aflatoxin B2, found in the livers, kidneys, blood, faeces, urine and milk of mammals that have consumed aflatoxin B2 contaminated feeds or foods. Also occurs in human milk. Aflatoxin M2 is considerably less toxic than aflatoxin M1. Produced in small quantities by Aspergillus flavus and parasiticus.

Aflatoxin Q1: The 3-hydroxy derivative and major metabolite of aflatoxin B1 in humans, rats and primates. Considerably less toxic than aflatoxin B1.

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Related terms:

Aflatoxicosis: Mycotoxicosis caused by ingestion of aflatoxins in contaminated foods and feeds.
Mycotoxicosis: Disease of humans and animals resulting from the ingestion of mycotoxins in foods or feeds.
Mycotoxins: Toxins, e.g. aflatoxins and ochratoxins, produced by fungi.
Toxins: Poisonous substances, especially those that are produced by one living organism, and are poisonous to other living organisms.

Data around aflatoxins in FSTA

FSTA, our dedicated food science and health database, currently holds approximately 9,000 records related to aflatoxins, including the following examples:

Title: Aflatoxin B1: a review on metabolism, toxicity, occurrence in food, occupational exposure, and detoxification methods.
Authors: Rushing, B. R.; Selim, M. I.
Source: Food and Chemical Toxicology; Vol. 124, February 2019. 81–100.
Peer reviewed: Yes
DOI: 10.1016/j.fct.2018.11.047
Title: Determination of aflatoxins in edible oils from China and Ethiopia using immunoaffinity column and HPLC-MS/MS.
Authors: Lingyun Chen; Molla, A. E.; Getu, K. M.; Ma, A.; Chengsong Wan
Source: Journal of AOAC International; Vol. 102 (1), February 2019. 149–155.
Peer reviewed: Yes
DOI: 10.5740/jaoacint.18-0106
Title: Aflatoxin M1 in cow, sheep, and donkey milk produced in Sicily, Southern Italy.
Authors: Cammilleri, G.; Graci, S.; Collura, R.; Buscemi, M. D.; Vella, A.; Macaluso, A.; Giaccone, V.; Giangrosso, G.; Cicero, A.; Dico, G. M. lo; Pulvirenti, A.; Cicero, N.; Ferrantelli, V.
Source: Mycotoxin Research; Vol. 35 (1), January 2019. 47–53.
Peer reviewed: Yes
DOI: 10.1007/s12550-018-0329-y

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References

[1] Coppock, R., Christian, R. and Jacobsen, B. (2018) Veterinary Toxicology. Basic and Clinical Principles. 3rd edn. Academic Press, p. Chapter 69.

[2] Richard, J. (2008) "Discovery of aflatoxins and significant historical features", Toxin Reviews, 27(3-4), pp. 171-201. DOI: 10.1080/15569540802462040.

[3] Kowalska, A. et al. (2017) "Aflatoxins: characteristics and impact on human health", Postępy Higieny i Medycyny Doświadczalnej, 71(1), pp. 0-0. DOI: 10.5604/01.3001.0010.3816.

[4] Aflatoxins (2018). Available at: https://www.who.int/foodsafety/FSDigest_Aflatoxins_EN.pdf (Accessed: 11 February 2019).

[5] Fink-Gremmels, J. (2008) "Mycotoxins in cattle feeds and carry-over to dairy milk: A review", Food Additives & Contaminants: Part A, 25(2), pp. 172-180. DOI: 10.1080/02652030701823142.

[6] IFIS Publishing. (2009) IFIS Dictionary of Food Science and Technology. 2rd edn. Oxford: Wiley-Blackwell. (Small updates made by Taylor, G, co-author of original text at IFIS Publishing, March 2019).

'Peanuts' photograph by Vladislav Nikonov on Unsplash, 'Cornfield' photograph by Milada Vigerova on Unsplash.

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