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Aflatoxin is a potent human carcinogen. It is a naturally occurring toxic metabolite produced by certain fungi (Aspergillus flavis), a mold found on food products such as corn and peanuts, peanut butter. It acts as a potent liver carcinogen in rodents (and, presumably, humans). They are probably the best known and most intensively researched mycotoxins in the world. Aflatoxins have been associated with various diseases , such as aflatoxicosis , in livestock , domestic animals and humans throughout the world .
The occurrence of aflatoxins is influenced by the weather, (temperature, and humidity - warm & wet is worst!); so the extent of contamination will vary with geographic location , agricultural and agronomic practices, and the susceptibility of the peanuts (etc.) to fungus before they are harvested, and during storage, and/or processing periods . Aflatoxins have received greater attention than any other mycotoxins because they clearly have a potent carcinogenic effect in laboratory rats and their acute poisonous effects in humans .
In the 1960 more than 100,000 young turkeys on poultry farms in England died in the course of a few months from an apparently new disease that was termed "Turkey X disease" . It was soon found that the difficulty was not limited to turkeys . Ducklings and young pheasants were also affected and heavy mortality was experienced .
A careful survey of the early outbreaks showed that they were all associated
with feeds, namely Brazilian peanut meal . An intensive investigation of the
suspect peanut meal was undertaken and it was quickly found that this peanut
meal was highly toxic to poultry and ducklings with symptoms typical of Turkey X
Speculations made during 1960 regarding the nature of the toxin suggested that it might be of fungal origin. In fact, the toxin-producing fungus was identified as Aspergillus flavus (1961) and the toxin was given the name Aflatoxin by virtue of its origin (A.flavis--> Afla).
This discovery has led to a growing awareness of the potential hazards of these substances as contaminants of food and feed causing illness and even death in humans and other mammals.
U.S. FDA Action Levels for Aflatoxins
Level (in ng/g)
|All products, except milk, designated for humans||20|
|Corn for immature animals and dairy cattle||20|
|Corn for breeding beef cattle, swine and mature poultry||100|
|Corn for finishing swine||200|
|Corn for finishing beef cattle||300|
|Cottonseed meal (as a feed ingredient)||300|
|All feedstuff other than corn||20|
Even though absolute safety can never be achieved , many countries have attempted to limit exposure to aflatoxins by imposing regulatory limits on commodities intended for use as food and feed .
More importantly, research supported by our institute has provided clear evidence that aflatoxin ingestion through contaminated foodstuffs is one of the major etiological factors in human hepatocellular carcinoma (HCC) in China and sub-Saharan Africa. In certain regions of these countries, at least 250,000 deaths from HCC occur annually.
Aflatoxin is a naturally occurring mycotoxin produced by two types of mold: Aspergillus flavus and Aspergillus parasiticus. Aspergillus flavus is common and widespread in nature and is most often found when certain grains are grown under stressful conditions such as drought. The mold occurs in soil, decaying vegetation, hay, and grains undergoing microbiological deterioration and invades all types of organic substrates whenever and wherever the conditions are favorable for its growth. Favorable conditions include high moisture content and high temperature. At least 13 different types of aflatoxin are produced in nature with aflatoxin B1 considered as the most toxic. While the presence of Aspergillus flavus does not always indicate harmful levels of aflatoxin it does mean that the potential for aflatoxin production is present.
Evidence that aflatoxin ingestion through contaminated foodstuffs is one of the major etiological factors in human hepatocellular carcinoma (HCC) in China and sub-Saharan Africa. In certain regions of these countries, at least 250,000 deaths from HCC occur annually. A natural progression from the etiological studies discussed is the introduction of preventive strategies to reduce the risk of liver cancer by exposure to aflatoxin. Investigators funded by NIEHS (Groopman, P01ES06052, P30ES03819) initiated a Phase II Oltipraz chemoprevention trial in China to define a dose and schedule of Oltipraz for reducing levels of validated aflatoxin biomarkers and to characterize dose-limiting toxicities. Oltipraz reduces the biologically effective dose of aflatoxin by inhibiting its activation by P450s and by inducing detoxification pathways. Preliminary results show a small but significant reduction of aflatoxin-albumin adducts at the highest dose level. Another intervention using chlorophyllin is also planned. Chlorophyllin is a water soluble derivative of chlorophyll that forms molecular complexes with aflatoxin and thereby reduces its bioavailability. Modulation of blood and urine aflatoxin biomarkers will be studied.
Aflatoxins often occur in crops in the field prior to harvest . After harvest contamination can occur if crop drying is delayed and during storage of the crop if the crop is keep too moist. Insect or rodent infestations facilitate mold invasion of some stored commodities.
Aflatoxins are detected occasionally in milk, cheese, corn, peanuts, cottonseed, nuts, almonds, figs, spices, and a variety of other foods and feeds . Milk, eggs, and meat products are sometimes contaminated because of the animal consumption of aflatoxin-contaminated feed . However, the commodities with the highest risk of aflatoxin contamination are corn, peanuts, and cottonseed
Corn is probably the commodity of greatest worldwide concern , because it is grown in climates that are likely to have perennial contamination with aflatoxins and corn is the staple food of many countries . However, procedures used in the processing of corn help to reduce contamination of the resulting food product . This is because although aflatoxins are stable to moderately stable in most food processes , they are unstable in processes such as those used in making tortillas that employ alkaline conditions or oxidizing steps . Aflatoxin-contaminated corn and cottonseed meal in dairy rations have resulted in aflatoxin M1 contaminated milk and milk products , including non-fat dry milk , cheese , and yogurt .
Humans are exposed to aflatoxins by consuming foods contaminated with products of fungal growth . Such exposure is difficult to avoid because fungal growth in foods is not easy to prevent . Even though heavily contaminated food supplies are not permitted in the market place in developed countries, concern still remains for the possible adverse effects resulting from long-term exposure to low levels of aflatoxins in the food supply .
Evidence of acute aflatoxicosis in humans has been reported from many parts of the world , namely the Third World Countries, like Taiwan, Ouganda, India, and many others . The syndrome is characterized by vomiting, abdominal pain, pulmonary edema, convulsions, coma, and death with cerebral edema and fatty involvement of the liver , kidneys , and heart.
Conditions increasing the likelihood of acute aflatoxicosis in humans include limited availability of food, environmental conditions that favor fungal development in crops and commodities, and lack of regulatory systems for aflatoxin monitoring and control.
Because aflatoxins, especially aflatoxin B1, are potent carcinogens in some animals, there is interest in the effects of long-term exposure to low levels of these important mycotoxins on humans . In 1988, the IARC placed aflatoxin B1 on the list of human carcinogens. This is supported by a number of epidemiological studies done in Asia and Africa that have demonstrated a positive association between dietary aflatoxins and Liver Cell Cancer (LCC) . Additionally , the expression of aflatoxin-related diseases in humans may be influenced by factors such as age, sex, nutritional status, and/or concurrent exposure to other causative agents such as viral hepatitis (HBV) or parasite infestation.
So what can you do to avoid aflatoxins?
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