Food for thought about mycotoxins, organic and genetically modified foods.
Authors: Marasas W. F. O. , Vismer H. F. 
Published: November 2017

Abstract

Food safety is an issue that is becoming increasingly important in national and international debates about agriculture, nutrition and health. Food safety is a complex and many-faceted issue. Three of these facets are food-borne toxic metabolites of fungi (mycotoxins), organically grown foods (organic foods) and genetically modified foods (GM-foods). Although there are different definitions and perceptions of "organic agriculture", the fact is that there is an increasing demand for organic foods in developed countries. Some people may argue that people in developing countries have always been eating organic foods. Be that as it may, the fact is that foods that are grown without the use of insecticides and fungicides may be expected to be infested by insects and infected by fungi to a larger extent than conventionally grown foods and concomitantly contaminated with higher levels of mycotoxins. A good example of this situation is patulin produced by the postharvest fungus, Penicillium expansum, in damaged or stored apples. In the case of conventionally grown apples, patulin levels in apple juice have been reported to range from 240-4000 µg/litre. Conversely, in organically produced apple cider, levels of up to 45 000 µg/litre were found. In organically produced apples, fewer apples were marketable, fungal rot was higher and the incidence of particularly P. expansum was increased over a short storage period. On the other hand, significant reductions in fumonisins produced by Fusarium verticillioides and F. proliferatum in genetically modified Bt-maize hybrids compared with standard maize lines have been achieved. Toxin-producing fungi, including Aspergillus flavus, A. ochraceaus, Fusarium verticillioides, F. graminearum, Penicillium expansum and their mycotoxins, such as aflatoxin B1, fumonisins and patulin, have been noted to occur in health foods such as nuts, oilseeds, muesli, cereals and partially milled rice, further posing a threat to human health. Serious health risks, such as liver cancer, may arise where mycotoxins are not controlled effectively in bulk productions of food commodities, such as aflatoxin in groundnut butter. Recently, groundnut butter used in the Primary Schools Nutrition Programme in South Africa was reported to contain high levels of aflatoxin. It is of great concern that the liver-cancer risk increases significantly if a child with hepatitis B infection consumes aflatoxin-contaminated foodstuffs such as groundnut butter at school and/or subsistence home-grown groundnuts at home. The statistics for mycotoxins in organic and health foods in South Africa and many other countries worldwide are still very limited, and should be further researched. The use of fungi and yeasts as biocontrol measures is also of concern, due to the emergence of fungi previously not considered important in human disease. In summary, it can be said that mycotoxin levels are generally higher in organically grown crops; that genetically modified crops can reduce mycotoxin levels significantly; that pesticides, in cases where insect infestations lead to fungal infections, reduce mycotoxin contamination; that fungicides are applied to control plant pathogenic fungi, and consequently lead to mycotoxin reduction; and that biological control is a concern with regard to emerging medically important fungi and the immune-compromised human host, as is the case in HIV/AIDS.