Monday, July 03, 2017

Defining Consensus Regarding the Safety of Genetically Modified Foods

The World Health Organization, the American Medical Association, and the National Academy of Sciences have all issued statements regarding the safety of foods derived from genetically engineered crops. However, in a recent letter critical of the documentary film Food Evolution, the following paper is cited:

No scientific consensus on GMO safety. Environmental Sciences Europe. 2015 27:4

This was the first time I had seen this paper so I spent some time going through it to see what kinds of arguments were being made. Below are a few excerpts and some discussion.

"the scarcity and contradictory nature of the scientific evidence published to date prevents conclusive claims of safety, or of lack of safety, of GMOs. Claims of consensus on the safety of GMOs are not supported by an objective analysis of the refereed literature."
"The health, environment, and agriculture authorities of most nations recognize publicly that no blanket statement about the safety of all GMOs is possible and that they must be assessed on a 'case-by-case' basis."

"There are no epidemiological studies investigating potential effects of GM food consumption on human health"

"an expert panel of the Royal Society of Canada issued a report that was highly critical of the regulatory system for GM foods and crops in that country. The report declared that it is 'scientifically unjustifiable' to presume that GM foods are safe without rigorous scientific testing and that the 'default prediction' for every GM food should be that the introduction of a new gene will cause 'unanticipated changes' in the expression of other genes, the pattern of proteins produced, and/or metabolic activities."

"We support the application of the Precautionary Principle with regard to the release and transboundary movement of GM crops and foods."

 I have not had a chance to check every single reference and citation made. However the general framework sketched out in the paper I am getting is this:

  • there is no absolute or conclusive evidence that genetically engineered foods are safe or unsafe
  • the risks are associated with unintended effects related to gene insertions (i.e. genetic disruptions)
  •  invocation of the precautionary principle is used to obviate the statements often cited by the World Health Organization, the American Medical Association, and the National Academy of Sciences

This leads me to ask, can we make a blanket statement about the safety of all conventionally modified or organic foods that utilize plant breeding and mutagenesis? Have there been epidemiological studies investigating the effects of these methods on human health?

Suddenly this thinking brings up a question I have addressed before: why would we invoke the precautionary principle in the case of  food from genetically engineered crops and not for conventionally and mutagenically improved crops? 

From the literature:

“We found that the improvement of a plant variety through the acquisition of a new desired trait, using either mutagenesis or transgenesis, may cause stress and thus lead to an altered expression of untargeted genes. In all of the cases studied, the observed alteration was more extensive in mutagenized than in transgenic plants” - (Batista, et al; 2008)

With greater disruptions, critics might favor increased regulatory scrutiny. However, we do not have a framework in place for mutagenically improved crop varieties that have been safely used for decades and approved by the organic food industry and accepted by consumers, nor do we have anything like this for conventionally bred crops. If an argument for the precautionary principle holds for genetically engineered crops on this basis, then it should also hold for all types of crop improvement.

Therefore it seems tenuous to make a scientific risk based justification for special treatment of genetically engineered crops without further evidence. When many refer to a consensus on the safety of genetically engineered foods, this is what I have in mind.

Policies related to genetically engineered foods leveraging the precautionary principle could lead to increased risk of doing more harm than good to human health and the environment if policies prevent or delay adoption of traits that could decrease use of toxic pesticides, or reduce carbon emissions and improve soil conservation as some biotech traits have been shown to do in the literature.

See also:

Fat Tails, The Precautionary Principle, and GMOs
Comments on Rules for Gene Editing Technology
Organic Activists Realize Hypocrisy in Opposition to Gene Editing Technology


Batista R, Saibo N, Louren├žo T, Oliveira MM. Microarray analyses reveal that
plant mutagenesis may induce more transcriptomic changes than transgene
insertion. Proc Natl Acad Sci U S A. 2008 Mar 4;105(9):3640-5. doi:
10.1073/pnas.0707881105. PubMed PMID: 18303117; PubMed Central PMCID: PMC2265136

Baudo MM, Lyons R, Powers S, Pastori GM, Edwards KJ, Holdsworth MJ, Shewry PR. (2006). Transgenesis has less impact on the transcriptome of wheat grain than conventional breeding. Plant Biotechnol J. 2006 Jul;4(4):369-80

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