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Genetically engineered foods: a threat to
human health?
Encontro de Investigadores, Ciência 2009
Rita Batista
Which GM foods are under commercialization in EU?
5 plant species approved for human consumption:
Soya (drinks, tofu, oil, flour, lecitin…)
Maize (oil, flour, syrup, sweet maize, cereals, etc…)
Oilseed rape (oil)
Cotton (oil)
Sugar beet (sugar)
2 types of genes introduced :
Herbicide tolerance/resistance (CP4EPSPS and PAT
genes)
Insect resistance (Cry genes)
What are the major health concerns of GE plants ?
Putative horizontal transfer
Despite:
Natural prevalence of antibiotic resistance in soil and enteric bacteria
The concern persists:
Transfer of antibiotic marker genes to gastrointestinal bacteria or
bacteria we eat together with food
Food processing
DNA breakdown
Passage through gastrointestinal tract
Bacterial restriction enzymes
Recipient bacteria → take up and integrate DNA into their genome
DNA → associated with appropriate regulatory sequences
Transferred trait → confer competitive advantage
No scientific evidence for uptake ingested DNA by
gastrointestinal bacteria as consequence of food consumption
Putative transgene horizontal transfer
Another concern:
Inactivation of orally administered antibiotic by the resistance markers
Directly
By integration of antibiotic resistance marker genes in gut
epithelial cells
nptII
most common ARM gene
From E. coli → ubiquitous in nature
Rapidly inactivated by stomach acid and degraded by
digestive enzymes
Confers resistance to antibiotics with no therapeutic relevance
Argument of a putative increase of antibiotic resistance by
gastrointestinal bacteria due to nptII HT is unacceptable
Putative transgene horizontal transfer
Inactivation of orally administered antibiotic by marker gene product
By integration of antibiotic resistance marker genes in
gut epithelial cells
Gastrointestinal epithelial cells do not divide and have a short life
span (7 days)
Integration of antibiotic resistance marker genes in gut epithelial
cells would not compromise public health
Putative transgene horizontal transfer
Despite:
No expert panel has ever identified a significant risk
associated with antibiotic resistance marker genes use
Efforts aimed to produce ARM free GM plant products
Removal of these genes after transgenic plant selection
Use of intron-containing marker genes
Use of antibiotic resistance plant genes
Consumption of “foreign” DNA
Consumption of DNA from foreign species (i.e. viruses or bacteria)
in the genome of a food plant
Bacteria and viruses always present in our food
All DNAs are chemically equivalent
Potential risk of DNA consumption would not depend on the
species of origin → only on its sequence
Consumption of “foreign” DNA
CaMV35Spro lead to inappropriate over expression of genes in
species to which it is transferred?
Several barriers would limit potential interaction of CaMV35Spro
with human DNA
CaMV is present in 10% cabbages and cauliflowers
CaMV infects most plant cells and produces 105 particle per cell
(each with one copy of 19Spro and 35Spro)
Consumption of any CaMV-infected vegetables result in
ingestion of far more copies of 35S pro than consumption of
transgenic plants carrying this promoter
Unexpected alterations in nutritional composition
GE cause unexpected and/or undesired effects in nutritional
composition of final product?
Concern also valid for plants obtained through conventional
breeding techniques
GM foods nutritional and biochemical characteristics are tested
before its commercialization
Allergenicity/ toxicity
Products of introduced genes represent allergens and/or toxins or
induce unintended effects on plant metabolism that lead to
upregulated expression of allergens and/or toxins?
Studies claiming for higher toxicity/ allergenicity of GE foods
tainted with important flaws
Two allergenicity problems promptly detected by regulatory
systems
Pioneer Hi-Bred GE soybean variety
Aventis Starlink GE maize variety
To date, no experimental evidence has supported a higher
degree of toxicity/ allergenicity of approved GE foods as
compared to their non-transgenic counterparts
What are our major research interests in this issue?
Are GM foods more allergenic than conventional?
Does genetic engineering provoke more alterations
than other modern conventional breeding techniques?
How important is natural plant variability in the
context of the food safety assessment process?
Contribute to fill the lack of scientific data
Develop highthrouput methodologies to check for the
safety of genetically modified foods
What have been the major conclusions obtained so far?
Probability of an individual having eaten GM food near
100%
None of the tested products have presented increased
allergenicity after genetic modification
Transcriptome alterations due to genetic modification were
< for transgenic vs mutagenized plants
Safety assessment of improved plant varieties
should be carried out on a case-by-case basis
and not simply restricted to foods obtained
through genetic engineering
The beginning…