Genetically engineered foods: a threat to human health?

Encontro de Investigadores, Ciência 2009

Rita Batista

Which GM foods are under commercialization in EU?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)

2 types of genes introduced :

Insect resistance (Cry genes)

Herbicide tolerance/resistance (CP4EPSPS and PAT genes)

Sugar beet (sugar)

What are the major health concerns of GE plants ?What are the major health concerns of GE plants ?

Putative horizontal transferPutative horizontal transfer

Transfer of antibiotic marker genes to gastrointestinal bacteria or bacteria we eat together with food

Natural prevalence of antibiotic resistance in soil and enteric bacteria

DNA breakdown

Recipient bacteria → take up and integrate DNA into their genome

DNA → associated with appropriate regulatory sequences

Transferred trait → confer competitive advantage

Despite:

The concern persists:

Food processing

Passage through gastrointestinal tract

Bacterial restriction enzymes

No scientific evidence for uptake ingested DNA by gastrointestinal bacteria as consequence of food consumption

Putative transgene horizontal transferPutative 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

most common ARM gene

Rapidly inactivated by stomach acid and degraded by digestive enzymes

From E. coli → ubiquitous in nature

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

nptII

Putative transgene horizontal transferPutative 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

No expert panel has ever identified a significant risk associated with antibiotic resistance marker genes use

Despite:

Putative transgene horizontal transferPutative transgene horizontal transfer

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” DNAConsumption 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” DNAConsumption of “foreign” DNA

CaMV35Spro lead to inappropriate over expression of genes in species to which it is transferred?

Consumption of any CaMV-infected vegetables result in ingestion of far more copies of 35S pro than consumption of

transgenic plants carrying this promoter

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)

Unexpected alterations in nutritional compositionUnexpected 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/ toxicityAllergenicity/ toxicity

To date, no experimental evidence has supported a higher degree of toxicity/ allergenicity of approved GE foods as

compared to their non-transgenic counterparts

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

What are our major research interests in this issue?What are our major research interests in this issue?

Are GM foods more allergenic than conventional?Are GM foods more allergenic than conventional?

Does genetic engineering provoke more alterations Does genetic engineering provoke more alterations than other modern conventional breeding techniques?than other modern conventional breeding techniques?

How important is natural plant variability in the How important is natural plant variability in the context of the food safety assessment process?context of the food safety assessment process?

Develop highthrouput methodologies to check for the safety of genetically modified foods

Contribute to fill the lack of scientific data

What have been the major conclusions obtained so far?What have been the major conclusions obtained so far?

None of the tested products have presented increased None of the tested products have presented increased allergenicity after genetic modificationallergenicity after genetic modification

Transcriptome alterations due to genetic modification were Transcriptome alterations due to genetic modification were < for transgenic < for transgenic vsvs mutagenized plants 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

Probability of an individual having eaten GM food near Probability of an individual having eaten GM food near 100%100%

The beginning…