Natural Toxins in Food

Natural toxins in food are plant secondary metabolites, bacterial toxins, phycotoxins (chemicals produced by algal cells) and mycotoxins.

Mycotoxins are secondary metabolites of fungi toxic to animals and humans. While only a small number of plant pathogenic fungal species are known to produce mycotoxins, most spoilage fungi secrete a range of toxic metabolites. The most important fungal genera producing mycotoxins that are found in food products are Aspergillus, Fusarium, Alternaria and Penicillium. Mycotoxin derivatives that are undetectable by conventional analytical techniques because their structure has been changed in the plant are called masked mycotoxins. Food processing, can on the other hand also chemically alter mycotoxins, but no step in the milling processes destroys mycotoxins. Some transformations that generate masked mycotoxins may lead to a decrease of toxicity.1

Among the various mycotoxins found in crops used for food and feed production, the trichothecenes toxin deoxynivalenol (DON or vomitoxin) is one of the most common and hazardous. The primary toxic effect of DON is inhibition of protein synthesis. In addition to native toxins, food also contains a large amount of plant and fungal derivatives of DON, including acetyl-DON, glucoside-DON (D3G), and potentially animal derivatives such as glucuronide metabolites present in animal tissues (blood, muscle and liver tissue). DON is one of the most common food-associated mycotoxins, particularly in cereals and cereal-derived products. In the US, 73% and 92% of wheat and corn samples, respectively, were found positive for DON. In Europe, food studies have shown that DON was present in 57% of all samples. The presence of DON in wheat decreases grain quality by rendering the crop unsuitable and unsafe for food, feed and malting process. Fungal contaminations have in fact been correlated with the beer “gushing” phenomenon, or the over-foaming of beer bottles bursting out the content. On the other hand, concentration of mycotoxins in animal feeds (bran, flour shorts screenings and middlings) compared to that in wheat grain may be up to 800% but more typically ranges from 150% to 340%.4

In addition to its prevalence, DON is one of the most hazardous food-associated mycotoxins. The ingestion of DON has been associated with vomiting, reduced weight gain, bleeding, skin lesions, anorexia, abdominal pain, diarrhea, malnutrition, headache and dizziness. Toxicity of DON relies on its ability to cross the intestinal and blood-brain barriers.2. In many animals bacteria convert toxic DON into its non-toxic metabolite DOM-1 and poultry, cows and sheep are almost insensitive to oral intoxication by DON. Humans on the other hand do not have intestinal bacteria that possess the ability to detoxify DON.3

Fusarium species fungal organism.
Fusarium species fungal organism (CDC/ Dr. Hardin)

Also, DON affects the plant metabolism in wheat because it leads to the inhibition of germination and decreases plant growth. The plant starts to develop a detoxification mechanism in which DON is glycosylated into 3-β-d-glucopyranosil-4-deoxynivalenol (D3G) and stored inside the vacuole or cell wall to combat this situation. This product is known as a “masked” mycotoxin, because one or more glucose molecules bind to the DON which reduces its toxicity in the plant and makes it unable to be detected by traditional methods for DON detection. D3G, in single cases, can even exceed the concentration of the native toxin in cereals and often results in high DON concentration in beers.3



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DON exposure adversely affects several types of immune system cells and could indirectly favor the emergence of tumors through a decrease in the immune vigilance associated to natural killer cells. At high doses, DON kills lymphocytes, leading to immuno-suppression, increased susceptibility to infection, reactivation of latent infections and decreased vaccine efficiency.

DON affects the nervous and the endocrine systems. It disrupts the production of several hormones causing reproductive disorders and increases proinflammatory molecules in the brain.

Biological control of DON contamination is emerging as a green approach. Functional BCAs include antagonistic microbes, natural fungicides derived from plants which inhibit the development and mycotoxin production, and enzymes from beneficial organisms for DON detoxification after production.

References

  1. Masked mycotoxins: A review. Franz Berthiller, Colin Crews, Chiara Dall'Asta, Sarah De Saeger, Geert Haesaert, Petr Karlovsky, Isabelle P Oswald, Walburga Seefelder, Gerrit Speijers, and Joerg Stroka
  2. From the Gut to the Brain: Journey and Pathophysiological Effects of the Food-Associated Trichothecene Mycotoxin Deoxynivalenol. Marc Maresca
  3. Prevalence and effects of mycotoxins on poultry health and performance, and recent development in mycotoxin counteracting strategies. G. R. Murugesan, D. R. Ledoux, K. Naehrer, F. Berthiller, T. J. Applegate, B. Grenier, T. D. Phillips, and G. Schatzmayr
  4. Mycotoxin Contamination in the EU Feed Supply Chain: A Focus on Cereal Byproducts. Luciano Pinotti,* Matteo Ottoboni, Carlotta Giromini, Vittorio Dell’Orto, and Federica Cheli



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