Aflatoxins are naturally occurring secondary fungal metabolites that are produced by two species of fungus Aspergillus flavus and Aspergillus parasiticus that are found naturally all over the world. They can contaminate food crops and pose a serious health threat to humans and livestock. The Food and Agriculture Organization (FAO) estimated that 25% of the world’s crops are contaminated with aflatoxins

Health Hazards of Consumption of Aflatoxin Contaminated Foods

By Aween Nazeer

Aflatoxins are naturally occurring secondary fungal metabolites that are produced by two species of fungus Aspergillus flavus and Aspergillus parasiticus that are found naturally all over the world. They can contaminate food crops and pose a serious health threat to humans and livestock. The Food and Agriculture Organization (FAO) estimated that 25% of the world’s crops are contaminated with aflatoxins

Discovery of Aflatoxins

Aflatoxins were discovered in 1960s when more than 100,000 young turkeys died in England over the course of a few months from an apparently new disease that was termed Turkey-X disease. It was soon found that the mortality was not limited to turkeys. Ducklings and young pheasants were also affected. After a careful survey of the outbreaks, the disease was found to be associated with the Brazilian groundnut meal. An intensive study of groundnut meal revealed its toxic nature as it produced typical symptoms of Turkey-X disease when consumed by poultry and ducklings. A study on the nature of the toxin suggested its origin from the fungus Aspergillus flavus. Thus, the toxin was named “aflatoxin” by virtue of its origin from Aspergillus flavus.

Types of Aflatoxins

Aflatoxin consists of a group of 20 fungal metabolites. However only six of them are common i,e, B1, B2, G1, G2, M1 and M2.

  • B1, B2, G1, and G2 are found in plant-based foods.
  • M1and M2 are found in foods of animal origin.

Presence of Aflatoxins

Aflatoxins can be found in over a hundred kinds of agro-products and foods such as barley, oats, rye, maize, sorghum, corn, rice, peanut, cocoa, bread, spices, soy sauce, vinegar, plant oil, pistachio, tea, Chinese medicinal herb, egg, milk, feed etc.

Favorable Conditions for Aflatoxin Growth

The favorable conditions for aflatoxins growth include:

  1. A high moisture content (at least 70 %).
  2. A range of temperature (10-40 oC).
  3. A pH of 4-8.
  4. Other factors such as stress drought, insect infestation, damage and broken grain kernels.

 Health Effects of Aflatoxins on Human

The amount of aflatoxins consumed contributes to the mutagenic, carcinogenic, teratogenic, and immunosuppressive health effects in the body. Aflatoxicosis is a condition caused by aflatoxins in both humans and animals. It mainly occurs in two general forms:

  1. Acute primary aflatoxicosisis
  2. Chronic primary aflatoxicosis

Acute primary aflatoxicosisis

The acute primary aflatoxicosisis is produced when moderate to high levels of aflatoxins contaminated foods are consumed over a short period of time. Specific acute episodes of disease may include hemorrhage, acute liver damage, edema (fluid retention), alteration in digestion, absorption and/or metabolism of nutrients, and this can also lead possibly to malnutrition and rarely death.

Chronic Primary Aflatoxicosisis

The chronic primary aflatoxicosis is produced when low to moderate levels of aflatoxins contaminated foods are consumed over a long period of time. The effects are usually subclinical and are difficult to recognize. The chronic forms of aflatoxicosis include (1) teratogenic effects associated with congenital malformations and (2) mutagenic effects where aflatoxins cause changes or mutations in the genetic code, altering DNA and these changes can lead to chromosomal breaks, rearrangement of chromosome pieces, gain or loss of entire chromosomes, or changes within a gene.

Health Hazards of Consumption of Aflatoxin Contaminated Foods

Physiological Effects of Aflatoxins

Aflatoxins have been reported to affect the various body organs like the liver, kidneys, lungs, brain, testes and many endocrine and exocrine organs, the heart, skeletal muscles and the different body systems.

 

 

Effect of Aflatoxins on Central Nervous System

Aflatoxins have been reported to be toxic to various aspects of brain chemistry and their function. Aflatoxin causes a decrease in dopamine, serotonin and alterations in the levels of the precursor’s tyrosine and tryptophan. Deficiencies in these neurotransmitters lead to neurological symptoms such as dullness, restlessness, muscle tremor, convulsions, loss of memory, epilepsy, idiocy, loss of muscle coordination, and abnormal sensations.

Effect of Aflatoxins on Gastrointestinal Tract

Aflatoxins have been reported to cause digestive system effects such as diarrhea, vomiting, intestinal hemorrhage, and liver necrosis and fibrosis. Aflatoxins have been reported also to damage the integrity of the pancreas.

Effect of Aflatoxins on Respiratory System

Aflatoxins have been reported to have serious acute effects on the respiratory systems such as respiratory tract and lung cancers. Nose-only inhalation exposure to aflatoxins may suppress alveolar macrophage which release the tumor necrosis factor-alpha and impair systemic innate and acquired immune defenses as well as suppress peritoneal macrophage phagocytosis which may lead to suppression of respiratory tract defenses system.

Effect of Aflatoxins on Cardiovascular System

Aflatoxins have reported to have serious acute effects on the cardiovascular systems including vascular fragility and hemorrhaging in tissues as well as heart damage and teratogenic effects. It is reported that there is a decrease in protein content of the muscles of these tissues and organs as well as inhibition of their metabolic processes attributable by the aflatoxin consumption of contaminated foods.

Effect of Aflatoxins on Urinary System

Aflatoxin have been reported to develop nephrotoxicity , fatty and hemorrhagic kidney syndrome, thickening of the glomerular basement membrane, abnormal development of glomerular epithelial cells and degenerative changes in renal tubular cells, congestion and parenchyma hemorrhage.

Effect of Aflatoxins on Endocrine System

Aflatoxins have been reported to interfere with the functioning of the various endocrine gland by disrupting the enzymes and can cause various cancers in different endocrine glands like pituitary gland, kidneys, thyroid gland, ovaries, testes, thyroid gland, parathyroid glands and endocrine pancreas.

Effect of Aflatoxins on Reproductive System

Aflatoxins have been reported to disrupt the reproductive system in both male and female. They can interfere with the reproductive capabilities of sexes, causing sterility, infertility, and abnormal sperm, low sperm count, and/or affect hormone activity.

Effect of Aflatoxins on Immunity

Chronic consumption of aflatoxin-contaminated foods has been reported to cause immuno‐ suppression in humans as they affect both the cellular and humoral immune responses where they alter immunological parameters resulting in impairments in cellular immunity hence decreasing the host resistance to infections.

Control of Aflatoxin

Overall, an integrated approach, whereby aflatoxins are controlled at all stages from field to the table is required. A number of strategies can be used to reduce the risk of contamination such as preharvesting strategies i.e., using genetically resistant varieties of crops, good tillage and weeding practices, Proper timing of irrigation and harvest, appropriate use of fertilizers and crop rotation, biological controls chemical controls, Harvesting strategies i.e., controlling moisture content and minimizing exposure to mold spores, Post-harvest strategies i.e.,   proper drying and storage of potentially affected crop products.

Health Hazards of Consumption of Aflatoxin Contaminated Foods 1
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