Aflatoxins are potential health hazard for human and animals, as it is a common natural contaminant of food and feed. Its prevalence is greatest in parts of the world where the climate is hot and humid. The Aspergillus fungi which produce the mycotoxins survive best in heat and humidity. As a result, although the prevalence of Aflatoxin is greatest in the developing world, climate change and global warming may lead to an increase in the occurrence of both the fungi and its toxic metabolites in parts of the world with temperate climates, like Europe and the United States.
There are thousands of metabolites produced by filamentous fungi within the Aspergillus family, some of which are beneficial. However, approximately 400 of these metabolites have been deemed mycotoxins and are hazardous. There are four major types of Aflatoxin: B1, B2, G1, and G2; according to their fluorescent color under ultraviolet light (blue or green). Aspergillus parasiticus produces all four, while Asperigillus Flavus produces strains B1 and B2. They are mutagenic, carcinogenic, and teratogenic; causing cancer and reproductive and development toxicity.
Commonly Contaminated Crops
Major sources of Aflatoxin in the food supply are peanuts, pistachios, Brazil nuts, cottonseed and maize. Aflatoxin is also a common contaminant of cereals (oats, rice, wheat, corn, and rye), dried fruit, coffee and cocoa beans, and cassava. Spices and herbs are often contaminated but to a lesser extent, and the toxin can be found in fermented beverages such as beer, wine, and fruit juices. Aflatoxin can enter the meat and dairy food supply through contaminated animal feed.
Of the major four, Aflatoxin B1 is of principal concern to human health. It is classified as a Group 1 carcinogen, meaning it definitely causes cancer in humans.
Specifically, Aflatoxin B1 causes Hepatic (liver) cancer. When ingested by ruminant animals like cows, Aflatoxin B1 is metabolized in the liver to Aflatoxin M1, which may be excreted into the milk. Aflatoxin M1, is a Group 2B carcinogen, in that it is possibly carcinogenic to humans. There are set limits on the amount of Aflatoxin B1 that is allowed in the foods to which they normally contaminate, since it is not possible to completely remove them. In the case of milk and other dairy products no amount of Aflatoxin B1 should be present, trace amounts of its metabolite Aflatoxin M1 however are permissible.
Aflatoxin Mechanism of Action
The toxic mechanism of action for all aflatoxin involve oxidative stress, lipid peroxidation, mitochondrial damage, and cell death as a result of apoptosis (versus necrosis).
Toxic exposure may be an acute single exposure at high levels, or a chronic with low but persistent levels—chronic exposure is most common. In addition to causing liver cancer, Aflatoxin may also have adverse affects on the immune system. It is also known that when Aflatoxin and infection with Hepatitis B are present at the same time, they cooperate to induce Hepatocellular carcinoma. Hepatitis B is the leading cause of Hepatocellular carcinoma, which is the fifth greatest malignancy worldwide, and is most prevalent in developing countries. As such the presence of Aflatoxin in the food supply, primarily in developing regions of the world, make it a significant pubic health concern.
Various treatment methods have been devised for the removal of Aflatoxin from contaminated food and feed. The amount of aflatoxin can be greatly reduced, but it does not appear that it can be completed removed. Physical methods of reduction include milling, microwave heating, and irradiation (ultra-violet or gamma). Chemical treatments involve using binders and sequestering agents or ozonation. However, ozonation is a rather expensive chemical process. Lastly, biodegradation can be used to decontaminate crops. Biodegradation is a biological method involving the use bacteria to detoxify aflatoxins. Flavobacterium aurentiacum as well as Mycobacterium are capable of this. However, lactobacillus does not metabolize aflatoxins, it only binds the toxin.
Aflatoxin are a family of toxic metabolites which contaminate crops used for food and feed, in humans and animals respectively. Aflatoxin contamination and the fungi that produce the toxin are most common in developing nations and regions of the world where the climate is hot and humid. However, food supplies are regularly and increasing imported due to globalization. Likewise, global warming and climate change, may make it so that the environment here in the United States or parts of Europe favor the growth of aspergillus fungi, increasing the burden of their toxic metabolites in the environment, and food supply. Therefore, the public should have an awareness and an understanding of the presence of this natural toxin in the foods supply chain, especially with the increase in organic, vegetarian, and vegan dietary patterns.
6 thoughts on “Natural Food Contaminant: Aflatoxin”
This was so interesting to read (I’m a health science student) and so well-written, amazing job!
Hi! Thanks for the blog post. How can consumers tell which grains and nuts contain aflatoxins and which don’t? Also, I wasn’t familar with all the terms used in this blog post. What do the terms lipid peroxidation, oxidative stress and apoptosis mean and why are these things harmful?
You can’t see or smell aflatoxin, so you wouldn’t know based off of that. Mostly, your location matters… how the country you reside in regulates it. Oxidative stress and lipid peroxidation have to with reactive oxygen species being generated, which cause oxidation, which if you think about “antioxidants” you want to prevent or counteract oxidation, so its not a good thing. Lipid peroxidation would be an example of damage from oxidative stress, in which the lipids within the membranes of cells are broken down. Oxidative stress can lead to cell damage causing cell death. Apoptosis is a type of cell death, another type of cell death being necrosis.
Question…I come from a place and like to travel to places that are hot/humid. How would I or anyone avoid aflatoxins? Or are they harder to avoid in places like the West Indies? What can a vacationer/traveler do? What can the locals do?
Well how many foods would you really be consuming while on vacation that are potentially contaminated with aflatoxin? Also the risk is greatest to those who are constantly exposed by engaging in agricultural work with the land, and eating unprocessed peanuts for example and stuff like that. I wouldn’t worry heavily about it.