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[SANET-MG] no increased mycotoxin in organic food
Increased Mycotoxins in Organic Produce?
Prof. Joe Cummins exposes the propaganda campaign against organic food
that has little or no scientific basis; and genetic modification is not
the answer to reducing aflatoxin contamination
A fully referenced version of this paper is posted on ISIS members’
website. http://www.i-sis.org.uk
Corporate propaganda against organic produce
Mycotoxins are toxic metabolites produced by fungi. Mycotoxin poisoning
has been known since the beginning of agriculture and has taken a large
toll on humans and farm animals consuming contaminated crops. Mycotoxins
cause immunological effects, specific organ damage, cancer, and in some
cases, death. Agricultural workers may also suffer from skin and
respiratory exposure during crop harvest and storage. Mycotoxin
poisoning is a worldwide problem associated with maize, rice, tree nuts
and peanuts along with fresh fruits and vegetables.
Many countries regulate specific mycotoxins and most countries try to
limit exposure to the toxins [1]. Poor rural populations suffer greater
impacts from mycotoxin exposure than urban dwellers because the urban
food supplies have begun to be more strictly regulated [2].
Recently, pro-GM scientists in academia and biotech corporations have
been claiming that organic food and feed is more heavily contaminated
with mycotoxins than conventional and genetically modified foods, on
grounds that organic production does not use chemical fungicides, and
are hence more likely to be infected. But the United Nations Food and
Agriculture Organization (FAO) states [3] that, "studies have not shown
that consuming organic products leads to a greater risk of mycotoxin
contamination."
In fact, numerous publications support the comment of FAO; furthermore,
there is no evidence that organic foods are more contaminated than
conventional foods.
The fungal species of Fusarium, Penicillium, Aspergillus and
Stachybotrys are the main producers of mycotoxins. The genes for the
biosynthetic pathways for mycotoxin production are extensive and tend to
cluster on a few chromosomes, which are passed on through vertical or
horizontal gene transfer; in fungi, horizontal gene transfer is most
effective [4]. The structure, synthesis and biosynthesis of mycotoxins
such as fumonisin have been extensively analyzed [5].
Scientific studies refute corporate smear
The exaggerated claims about greatly elevated levels of mycotoxin in
organic foods on the internet or in news media have not been borne out
by the peer-reviewed scientific literature.
Ochratoxin, a toxin produced in Penicillium and Aspergillus, is mainly
found in grain, nuts and dried fruits and usually associated with
storage of such foods. The toxin damages the kidney, causes cancer and
immune suppression. Conventional and organic cereals on the Italian
market were compared and no differences were found between the two
agricultural practices [6]. Ochratoxin was evaluated in cereal baby
foods on the Italian market derived from integrated pest management,
organic and conventional farms. Cereals from integrated pest management
had no detectable toxin, those from conventional practices had elevated
toxin levels in multigrain and seminola-based cereal while only organic
rice-based cereal contained the toxin. The study concludes, however,
that there is no significant risk to children who occasionally consume
toxin contaminated at the observed levels [7].
Ochratoxin has also been found in the milk of cows consuming
contaminated grain. Norwegian milk and baby formula from organic and
conventional production was therefore compared. No toxin was found in
any of the infant formulae. But the toxin was detected in 6 out of 40
conventional milk samples and 5 out of 47 organic milk samples, the
highest level detected in conventional milk was twice the highest level
detected in organic milk [8].
Conventional and organic Italian foodstuffs made up of maize, wheat,
rice or mixed products were compared for the Fusarium toxins fumonisin
and deoxynivalenol. Fumonisin causes cancers of liver or kidney along
with blood disorders and pulmonary edema in farm and experimental
animals. Deoxynivalenol (vomitosin) causes anorexia at low levels and
vomiting at higher levels, and also damages the immune system. Both
organic and conventional foods contained the toxins, but more of the
conventional foods were contaminated than organic foods. The highest
deoxynivalenol levels were found in conventional rice-based foodstuffs
while the highest level of fumonisin was found in conventional
maize-based foodstuffs. Organic foodstuffs contained consistently lower
contamination than conventional foodstuffs [9].
A broad study including heavy metals, nitrates and mycotoxins in a range
organic and conventional foods in France found no significant
differences between organic and conventional foods in a number of
mycotoxins. One high level of patulin was observed in a sample of
organic apples but no values for patulin content in conventional apples
were reported in the study [10].
Patulin is produced by Penicillium and Aspergillus, and is known to
damage genes, cause birth defects, immune and neurological dysfunction.
No significant difference in patulin levels was found between organic
and conventional apple products [11]. Nevertheless, a report from
Science in Africa indicated that patulin was present in commercial apple
products and claimed that a study on organically produced apple cider
has found "levels up to 40,000 micrograms per liter". It used that
finding to make general claims about the unsafe practices in organic
agriculture [12]. Despite extensive and repeated literature searches, I
have been unable to locate a single peer-reviewed report documenting
such a huge level of toxin contamination. But that value has been
promulgated through a number of news media and web reports.
Genetic modification (GM) has been promoted as a means of preventing
mycotoxin contamination, particularly in maize. Several strategies have
been proposed but the only one deployed is to incorporate Bacillus
thuringiensis (Bt) toxin to prevent corn borer tunneling which
encourages fungal growth in maize [13]. Bt and conventional isogenic
maize was studied in France and Spain. Moderate to low levels of
mycotoxins were found on both GM and conventional maize but significant
differences were found in some areas [14]. The presence of mycotoxins in
Bt and conventional maize tested in central Europe concluded that under
European conditions the use of Bt maize will only slightly reduce
contamination of maize with mycotoxins produced by Fusarium fungi [15].
Aflatoxin is a mycotoxin of global significance
Aflatoxin is a naturally occurring mycotoxin that has attracted
worldwide attention because it is a powerful toxin that damages genes.
Two types pf mould - Aspergillus flavus and Aspergillus parasiticucus -
can produce the toxin. Aspergillus flavus is widespread in soil, and
mouldy grains and nuts are commonly contaminated with the fungus.
Aflatoxin production is favoured by moisture and high temperature. At
least 13 different types of aflatoxin are produced and the most potent
of these is aflatoxin B1. Grain testing for aflatoxin is provided by the
Grain Inspection Packers and stockyard administration of USDA at a cost
of $25 per test [16].
Liver cancer is the fifth most prevalent cancer in the world; and 80% of
the cases are in the developing world. The primary causes of liver
cancer in the developing world are the hepatitis B virus and aflatoxin,
and most ferociously, the two combined. Limiting the contamination of
foodstuffs by aflatoxin is a particularly important target for public
health [17]. However, aflatoxin contamination of food is also a major
problem in the developed world.
The biological strategies explored to reduce or eliminate aflatoxin in
food and feed include inoculating seeds with Aspergillus strains unable
to produce aflatoxin, to replace toxin-producing strains in the soil.
Crops resistant to Aspergillus are selected using traditional genetic
methods with molecular marker-assisted selection or by direct genetic
modification.
A workshop on aflatoxin elimination and fungal genomics provided an
overview on ecological and genetic approaches to controlling aflatoxin
[18]. Cotton seed is an important crop for oil and feed. Strains of
Aspergillus flavus without toxins were made to colonize sterile seed, a
treatment that reduced the proportion of toxin-contaminated seed by over
50% the first year, and more in later years, providing an economic
benefit to the producer [19]. Non-toxin strains of Aspergillus flavus
and Aspergillus parasiticus alone or in combination significantly
reduced aflatoxin content of peanuts, a mixture of the two types of
fungus being the most effective [20]. Intra-specific competition is the
basis of the biological control of aflatoxin. Sexually compatible
strains fuse to form mycelia that produce aflatoxin, while vegetative
incompatibility reactions result in the death of the fused mycelia
resulting in reduced aflatoxin production [21]. The strain of
Aspergillus flavus used to reduced aflatoxin in cotton has been found to
be defective in aflatoxin synthesis [22]. Growth and mycotoxin
production of Aspergillus flavus and Aspergillus parasiticus were
inhibited by extracts of Agave cactus (the cactus used in tequila).
Scaling up production of such natural inhibitors may be worthwhile [23].
Conventional plant breeding and conventional breeding using molecular
markers are being used to select for genes conferring resistance to
Aspergillus infection. Genetic resistance to Aspergillus and to
aflatoxin production have been identified in maize but more work is
needed to produce commercial varieties [24]. It is becoming clear that
traits for low aflatoxin production are quantitative trait loci (QTL)
involving the additive effects of many genes, rather than a qualitative
effect of one or a few genes. Such quantitative loci are the most
important kind of genes in plant breeding, governing plant size, yield
of grain, disease resistance, etc. QTL for low aflatoxin have been
identified in maize [25]. QTL have been pyramided (pyramiding is
combining genes from many strains into a single strain by crossing) in
maize combining resistance to Aspergillus with resistance to ear feeding
insects, which wound the maize and allow fungal infection to take place
[26]. QTL provide the most promising long term protection against
aflatoxin crop pollution.
Genetic engineering has focused on Bacillus thuringiensis (Bt) toxin to
reduce wounding of the crop to allow fungal infestation or on more
direct methods to limit fungal infestation. Maize was inoculated with
Aspergillus flavus and infested with corn borers, Bt strains produced
grain with less aflatoxin than isogenic lines lacking Bt [27]. The
experiment was interesting but employed artificial conditions, with
neither natural fungal infection nor borer infestation. Peanuts modified
with a Bt cry 1Ac gene were found to contain reduced levels of
aflatoxin. Peanuts were also modified with a bacterial choroperoxidase
gene that resisted Aspergillus infection and showed promise in producing
peanuts with reduced aflatoxin [28]. The bacterial chloroperoxidase gene
and several other candidate genes have been used to transform cotton but
data on their effectiveness in reducing aflatoxin has not yet been
obtained [29]. A gene for a ribosomal inhibiting protein (RIP) was
isolated from maize and used to transform peanut, RIP blocked fungal
ribosomes without inhibiting the ribosomes of maize, the effectiveness
of the modified peanut has not yet been tested [30]. In general the GM
crops are not yet fully tested for their ability to reduce aflatoxin
pollution of maize, peanut and cottonseed.
Conclusion
In conclusion, peer-reviewed publications indicate that organic foods
are not more hazardous sources of mycotoxins than conventional foods. On
the contrary, organic foods tend to be less contaminated, and may
provide protection from the toxins. The use of GM maize has not provided
major protection from mycotoxins in comparison to conventional maize.
There is a growing sense that the world of public relations has
unleashed a propaganda campaign against organic food that has little or
no scientific basis.
As far as aflatoxin is concerned, biological control using fungi unable
to make the toxin to control those that produce it has proved effective
in cotton, and conventional breeding using QTL to produce strains
resistant to fungal infestation has proved useful in maize. Genetic
modification has had preliminary success using Bt genes to prevent
insect wounding followed by fungal infestation, though the toxicity of
Bt genes and proteins is still untested and unknown [31]. Thus, the
biological control and conventional breeding methods are the most
immediately useful in reducing aflatoxin contamination of food and feed.
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