Dangers of toxicity
Aflatoxins are secondary metabolites produced by some fungi (fungi), notorious 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 hepatocarcinoma - when ingested in large quantities and for long periods - has been widely 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 the conservation of cereals does not respect satisfactory hygiene standards and liver diseases (such as hepatitis viral) are more common.
Aflatoxins in food
The foodstuffs most frequently contaminated by aflatoxins, both during cultivation and during harvesting and storage, are cereals, soybeans, legumes, cotton, some types of almonds and peanuts; often these substances do not give a visual trace of the their presence, however probable when the foodstuffs appear clearly moldy Aspergillus flavus (the most common in our latitudes), however, is not necessarily synonymous with aflatoxin contamination; these are in fact produced only if the humidity and temperature conditions are favorable. Similar assumptions are recorded, for example, in the fields of the Po Valley, where the humidity and heat of the summer period facilitate the contamination of corn, and especially in tropical and subtropical areas, where the drought climate favors the contamination of 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, lack of water, insufficient phytosanitary defense (especially in the case of the corn borer) and inadequate fertilization, while it is hindered by the "vegetable well-being". On the other hand, in a food immune from the presence of Aspergillus flavus, however, there may be mycotoxins, since these substances are particularly resistant to treatments, including those of 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, the aflatoxins accumulate in its meat and from these they pass to man through the consumption of steaks or other parts of animals (especially the liver); fortunately it is in any case of limited quantities, practically negligible. More worrying is the fact that aflatoxins are secreted, in proportionally reduced but still potentially dangerous quantities (such as aflatoxins M1 and M2, deriving from B1 and B2), in the milk of cows fed with contaminated feed; these aflatoxins they can therefore be transmitted to man both through the consumption of milk and through the consumption of its derivatives (yogurt and cheeses). Obviously, controls are rigorous, especially for milks intended for infants, in which tolerance limits are extremely low.
Impact on health and prevention
The toxicity of aflatoxins most likely stems from their ability to bind to nucleic acids and interfere with protein synthesis; in addition to the liver, these substances have a negative effect 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 how aflatoxins possess a "high fetotoxic and teratogenic activity (they are harmful and mutagenic to the fetus).
Currently, man has at his disposal important weapons in the fight against aflatoxins, ranging from the optimization of 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.
