Hazards of toxicity
Aflatoxins are secondary metabolites produced by some fungi (mycetes), sadly known for their toxic, carcinogenic and mutagenic power, and for being frequent food contaminants.
The toxicity of these molecules mainly affects the liver, to the point that their ability to induce hepatocellular carcinoma - when they are ingested in large quantities and for long periods - has been amply demonstrated. The damaging action of these toxins is accelerated by the simultaneous presence of chronic liver diseases; this would explain the higher incidence of liver cancer in developing countries, where cereal conservation does not meet satisfactory hygiene standards and liver diseases (such as viral hepatitis) are more common.
Aflatoxins in foods
The most frequently contaminated foodstuffs from aflatoxins, both during cultivation and during harvest and storage, are cereals, soy, legumes, cotton, some types of almonds and peanuts; often these substances do not give a visual trace of their presence, however probable when the foodstuffs appear obviously moldy. The presence in a food of Aspergillus flavus (the most common in our latitudes), however, is not necessarily synonymous with aflatoxin contamination; these are in fact produced only if the conditions of humidity and temperature are favorable. Similar assumptions are recorded, for example, in the fields of the Po Valley, where the humidity and the heat of the summer facilitate the contamination of the corn, and especially in the tropical and subtropical areas, where instead the drought climate favors the contamination of the crops. In general, the production of aflatoxins in the field is favored by the stress conditions to which the plant is subjected, such as high temperatures and humidity, water scarcity, insufficient phytosanitary defense (especially in the case of corn borer) and inadequate fertilization, while it is hampered by "vegetable well-being". On the other hand, in a food that is immune to the presence of Aspergillus flavus, mycotoxins may still be present, since these substances are particularly resistant to treatments, including pasteurization and sterilization, which only partially inactivate them.
Among the many characteristics of aflatoxins is the ability to be transmitted through the food chain; in practice, if an animal is fed with contaminated cereal-based feed, aflatoxins accumulate in its flesh and from these pass to humans through the consumption of steaks or other parts of animals (especially the liver); fortunately, however, these quantities are limited, practically negligible. More worrying is the fact that aflatoxins are secreted, to a proportionally reduced but potentially dangerous extent (such as aflatoxins M1 and M2, deriving from B1 and B2), in the milk of cows fed with contaminated feed; these aflatoxins can therefore be transmitted to humans both through the consumption of milk and through the consumption of its derivatives (yogurt and cheese). Obviously the controls are rigorous, above all for the milk destined to the newborns, in which the limits of tolerance are extremely reduced.
Repercussions on health and prevention
The toxicity of aflatoxins probably arises from their ability to bind to nucleic acids and to interfere with protein synthesis; In addition to liver disease, these substances act negatively on the immune system and promote the appearance of tumors even in extrahepatic sites (gall bladder, colon, salivary glands, lungs, kidney, rectum, stomach, subcutaneous and bone tissue). Finally, we recall that aflatoxins have a high fetotoxic and teratogenic activity (they are harmful and mutagenic to the fetus).
Currently the man has available important weapons in the fight against aflatoxins, ranging from the optimization of the controls and the phases of cultivation, harvesting and storage (including the choice of resistant hybrids), to the use of transgenic seeds, then genetically manipulated to be less susceptible to Aspergillus infestation.
